| Message ID | 529ec882-734f-17ae-e4cb-3aeb563ad1d5@bluespec.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | irqchip/sifive-plic: add irq_mask and irq_unmask | expand |
On Thu, 12 Sep 2019 14:40:34 PDT (-0700), Darius Rad wrote: > As per the existing comment, irq_mask and irq_unmask do not need > to do anything for the PLIC. However, the functions must exist > (the pointers cannot be NULL) as they are not optional, based on > the documentation (Documentation/core-api/genericirq.rst) as well > as existing usage (e.g., include/linux/irqchip/chained_irq.h). > > Signed-off-by: Darius Rad <darius@bluespec.com> > --- > drivers/irqchip/irq-sifive-plic.c | 13 +++++++++---- > 1 file changed, 9 insertions(+), 4 deletions(-) > > diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c > index cf755964f2f8..52d5169f924f 100644 > --- a/drivers/irqchip/irq-sifive-plic.c > +++ b/drivers/irqchip/irq-sifive-plic.c > @@ -111,6 +111,13 @@ static void plic_irq_disable(struct irq_data *d) > plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); > } > > +/* > + * There is no need to mask/unmask PLIC interrupts. They are "masked" > + * by reading claim and "unmasked" when writing it back. > + */ > +static void plic_irq_mask(struct irq_data *d) { } > +static void plic_irq_unmask(struct irq_data *d) { } > + > #ifdef CONFIG_SMP > static int plic_set_affinity(struct irq_data *d, > const struct cpumask *mask_val, bool force) > @@ -138,12 +145,10 @@ static int plic_set_affinity(struct irq_data *d, > > static struct irq_chip plic_chip = { > .name = "SiFive PLIC", > - /* > - * There is no need to mask/unmask PLIC interrupts. They are "masked" > - * by reading claim and "unmasked" when writing it back. > - */ > .irq_enable = plic_irq_enable, > .irq_disable = plic_irq_disable, > + .irq_mask = plic_irq_mask, > + .irq_unmask = plic_irq_unmask, > #ifdef CONFIG_SMP > .irq_set_affinity = plic_set_affinity, > #endif I can't find any other drivers in irqchip with empty irq_mask/irq_unmask. I'm not well versed in irqchip stuff, so I'll leave it up to the irqchip maintainers to comment on if this is the right way to do this. Either way, I'm assuming it'll go in through some the irqchip tree so Acked-by: Palmer Dabbelt <palmer@sifive.com> just to make sure I don't get in the way if it is the right way to do it :).
I had issues with that plic driver. The current implementation wasn't usable with driver using level sensitive interrupt together with the IRQF_ONESHOT flag. Those null were producing crashes in the chained_irq_enter function. Filling them with dummy function fixed the issue. On Sat, Sep 14, 2019 at 9:00 PM Palmer Dabbelt <palmer@sifive.com> wrote: > > On Thu, 12 Sep 2019 14:40:34 PDT (-0700), Darius Rad wrote: > > As per the existing comment, irq_mask and irq_unmask do not need > > to do anything for the PLIC. However, the functions must exist > > (the pointers cannot be NULL) as they are not optional, based on > > the documentation (Documentation/core-api/genericirq.rst) as well > > as existing usage (e.g., include/linux/irqchip/chained_irq.h). > > > > Signed-off-by: Darius Rad <darius@bluespec.com> > > --- > > drivers/irqchip/irq-sifive-plic.c | 13 +++++++++---- > > 1 file changed, 9 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c > > index cf755964f2f8..52d5169f924f 100644 > > --- a/drivers/irqchip/irq-sifive-plic.c > > +++ b/drivers/irqchip/irq-sifive-plic.c > > @@ -111,6 +111,13 @@ static void plic_irq_disable(struct irq_data *d) > > plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); > > } > > > > +/* > > + * There is no need to mask/unmask PLIC interrupts. They are "masked" > > + * by reading claim and "unmasked" when writing it back. > > + */ > > +static void plic_irq_mask(struct irq_data *d) { } > > +static void plic_irq_unmask(struct irq_data *d) { } > > + > > #ifdef CONFIG_SMP > > static int plic_set_affinity(struct irq_data *d, > > const struct cpumask *mask_val, bool force) > > @@ -138,12 +145,10 @@ static int plic_set_affinity(struct irq_data *d, > > > > static struct irq_chip plic_chip = { > > .name = "SiFive PLIC", > > - /* > > - * There is no need to mask/unmask PLIC interrupts. They are "masked" > > - * by reading claim and "unmasked" when writing it back. > > - */ > > .irq_enable = plic_irq_enable, > > .irq_disable = plic_irq_disable, > > + .irq_mask = plic_irq_mask, > > + .irq_unmask = plic_irq_unmask, > > #ifdef CONFIG_SMP > > .irq_set_affinity = plic_set_affinity, > > #endif > > I can't find any other drivers in irqchip with empty irq_mask/irq_unmask. I'm > not well versed in irqchip stuff, so I'll leave it up to the irqchip > maintainers to comment on if this is the right way to do this. Either way, I'm > assuming it'll go in through some the irqchip tree so > > Acked-by: Palmer Dabbelt <palmer@sifive.com> > > just to make sure I don't get in the way if it is the right way to do it :). > > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv
On Sat, 14 Sep 2019 12:42:32 PDT (-0700), charles.papon.90@gmail.com wrote: > I had issues with that plic driver. The current implementation wasn't > usable with driver using level sensitive interrupt together with the > IRQF_ONESHOT flag. > > Those null were producing crashes in the chained_irq_enter function. > Filling them with dummy function fixed the issue. I'm not arguing it fixes a crash, the code Darius pointed to obviously doesn't check for NULL before calling these functions and will therefor crash. There is a bunch of other code that does check, though, so I guess my question is really: is the bug in the PLIC driver, or in this header? If we're not allowed to have these as NULL and there's nothing to do, then this is a reasonable patch. I'm just not capable of answering that question, as I'm not an irqchip maintainer :) > On Sat, Sep 14, 2019 at 9:00 PM Palmer Dabbelt <palmer@sifive.com> wrote: >> >> On Thu, 12 Sep 2019 14:40:34 PDT (-0700), Darius Rad wrote: >> > As per the existing comment, irq_mask and irq_unmask do not need >> > to do anything for the PLIC. However, the functions must exist >> > (the pointers cannot be NULL) as they are not optional, based on >> > the documentation (Documentation/core-api/genericirq.rst) as well >> > as existing usage (e.g., include/linux/irqchip/chained_irq.h). >> > >> > Signed-off-by: Darius Rad <darius@bluespec.com> >> > --- >> > drivers/irqchip/irq-sifive-plic.c | 13 +++++++++---- >> > 1 file changed, 9 insertions(+), 4 deletions(-) >> > >> > diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c >> > index cf755964f2f8..52d5169f924f 100644 >> > --- a/drivers/irqchip/irq-sifive-plic.c >> > +++ b/drivers/irqchip/irq-sifive-plic.c >> > @@ -111,6 +111,13 @@ static void plic_irq_disable(struct irq_data *d) >> > plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); >> > } >> > >> > +/* >> > + * There is no need to mask/unmask PLIC interrupts. They are "masked" >> > + * by reading claim and "unmasked" when writing it back. >> > + */ >> > +static void plic_irq_mask(struct irq_data *d) { } >> > +static void plic_irq_unmask(struct irq_data *d) { } >> > + >> > #ifdef CONFIG_SMP >> > static int plic_set_affinity(struct irq_data *d, >> > const struct cpumask *mask_val, bool force) >> > @@ -138,12 +145,10 @@ static int plic_set_affinity(struct irq_data *d, >> > >> > static struct irq_chip plic_chip = { >> > .name = "SiFive PLIC", >> > - /* >> > - * There is no need to mask/unmask PLIC interrupts. They are "masked" >> > - * by reading claim and "unmasked" when writing it back. >> > - */ >> > .irq_enable = plic_irq_enable, >> > .irq_disable = plic_irq_disable, >> > + .irq_mask = plic_irq_mask, >> > + .irq_unmask = plic_irq_unmask, >> > #ifdef CONFIG_SMP >> > .irq_set_affinity = plic_set_affinity, >> > #endif >> >> I can't find any other drivers in irqchip with empty irq_mask/irq_unmask. I'm >> not well versed in irqchip stuff, so I'll leave it up to the irqchip >> maintainers to comment on if this is the right way to do this. Either way, I'm >> assuming it'll go in through some the irqchip tree so >> >> Acked-by: Palmer Dabbelt <palmer@sifive.com> >> >> just to make sure I don't get in the way if it is the right way to do it :). >> >> _______________________________________________ >> linux-riscv mailing list >> linux-riscv@lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/linux-riscv
On Thu, 12 Sep 2019 22:40:34 +0100, Darius Rad <darius@bluespec.com> wrote: Hi Darius, > > As per the existing comment, irq_mask and irq_unmask do not need > to do anything for the PLIC. However, the functions must exist > (the pointers cannot be NULL) as they are not optional, based on > the documentation (Documentation/core-api/genericirq.rst) as well > as existing usage (e.g., include/linux/irqchip/chained_irq.h). > > Signed-off-by: Darius Rad <darius@bluespec.com> > --- > drivers/irqchip/irq-sifive-plic.c | 13 +++++++++---- > 1 file changed, 9 insertions(+), 4 deletions(-) > > diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c > index cf755964f2f8..52d5169f924f 100644 > --- a/drivers/irqchip/irq-sifive-plic.c > +++ b/drivers/irqchip/irq-sifive-plic.c > @@ -111,6 +111,13 @@ static void plic_irq_disable(struct irq_data *d) > plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); > } > > +/* > + * There is no need to mask/unmask PLIC interrupts. They are "masked" > + * by reading claim and "unmasked" when writing it back. > + */ > +static void plic_irq_mask(struct irq_data *d) { } > +static void plic_irq_unmask(struct irq_data *d) { } This outlines a bigger issue. If your irqchip doesn't require mask/unmask, you're probably not using the right interrupt flow. Looking at the code, I see you're using handle_simple_irq, which is almost universally wrong. As per the description above, these interrupts should be using the fasteoi flow, which is designed for this exact behaviour (the interrupt controller knows which interrupt is in flight and doesn't require SW to do anything bar signalling the EOI). Another thing is that mask/unmask tends to be a requirement, while enable/disable tends to be optional. There is no hard line here, but the expectations are that: (a) A disabled line can drop interrupts (b) A masked line cannot drop interrupts Depending what the PLIC architecture mandates, you'll need to implement one and/or the other. Having just (a) is indicative of a HW bug, and I'm not assuming that this is the case. (b) only is pretty common, and (a)+(b) has a few adepts. My bet is that it requires (b) only. > + > #ifdef CONFIG_SMP > static int plic_set_affinity(struct irq_data *d, > const struct cpumask *mask_val, bool force) > @@ -138,12 +145,10 @@ static int plic_set_affinity(struct irq_data *d, > > static struct irq_chip plic_chip = { > .name = "SiFive PLIC", > - /* > - * There is no need to mask/unmask PLIC interrupts. They are "masked" > - * by reading claim and "unmasked" when writing it back. > - */ > .irq_enable = plic_irq_enable, > .irq_disable = plic_irq_disable, > + .irq_mask = plic_irq_mask, > + .irq_unmask = plic_irq_unmask, > #ifdef CONFIG_SMP > .irq_set_affinity = plic_set_affinity, > #endif Can you give the following patch a go? It brings the irq flow in line with what the HW can do. It is of course fully untested (not even compile tested...). Thanks, M. From c0ce33a992ec18f5d3bac7f70de62b1ba2b42090 Mon Sep 17 00:00:00 2001 From: Marc Zyngier <maz@kernel.org> Date: Sun, 15 Sep 2019 15:17:45 +0100 Subject: [PATCH] irqchip/sifive-plic: Switch to fasteoi flow The SiFive PLIC interrupt controller seems to have all the HW features to support the fasteoi flow, but the driver seems to be stuck in a distant past. Bring it into the 21st century. Signed-off-by: Marc Zyngier <maz@kernel.org> --- drivers/irqchip/irq-sifive-plic.c | 29 +++++++++++++++-------------- 1 file changed, 15 insertions(+), 14 deletions(-) diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c index cf755964f2f8..8fea384d392b 100644 --- a/drivers/irqchip/irq-sifive-plic.c +++ b/drivers/irqchip/irq-sifive-plic.c @@ -97,7 +97,7 @@ static inline void plic_irq_toggle(const struct cpumask *mask, } } -static void plic_irq_enable(struct irq_data *d) +static void plic_irq_mask(struct irq_data *d) { unsigned int cpu = cpumask_any_and(irq_data_get_affinity_mask(d), cpu_online_mask); @@ -106,7 +106,7 @@ static void plic_irq_enable(struct irq_data *d) plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1); } -static void plic_irq_disable(struct irq_data *d) +static void plic_irq_unmask(struct irq_data *d) { plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); } @@ -125,10 +125,8 @@ static int plic_set_affinity(struct irq_data *d, if (cpu >= nr_cpu_ids) return -EINVAL; - if (!irqd_irq_disabled(d)) { - plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); - plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1); - } + plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); + plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1); irq_data_update_effective_affinity(d, cpumask_of(cpu)); @@ -136,14 +134,18 @@ static int plic_set_affinity(struct irq_data *d, } #endif +static void plic_irq_eoi(struct irq_data *d) +{ + struct plic_handler *handler = this_cpu_ptr(&plic_handlers); + + writel(d->hwirq, handler->hart_base + CONTEXT_CLAIM); +} + static struct irq_chip plic_chip = { .name = "SiFive PLIC", - /* - * There is no need to mask/unmask PLIC interrupts. They are "masked" - * by reading claim and "unmasked" when writing it back. - */ - .irq_enable = plic_irq_enable, - .irq_disable = plic_irq_disable, + .irq_mask = plic_irq_mask, + .irq_unmask = plic_irq_unmask, + .irq_eoi = plic_irq_eoi, #ifdef CONFIG_SMP .irq_set_affinity = plic_set_affinity, #endif @@ -152,7 +154,7 @@ static struct irq_chip plic_chip = { static int plic_irqdomain_map(struct irq_domain *d, unsigned int irq, irq_hw_number_t hwirq) { - irq_set_chip_and_handler(irq, &plic_chip, handle_simple_irq); + irq_set_chip_and_handler(irq, &plic_chip, handle_fasteoi_irq); irq_set_chip_data(irq, NULL); irq_set_noprobe(irq); return 0; @@ -188,7 +190,6 @@ static void plic_handle_irq(struct pt_regs *regs) hwirq); else generic_handle_irq(irq); - writel(hwirq, claim); } csr_set(sie, SIE_SEIE); }
On Sun, 15 Sep 2019 07:24:20 PDT (-0700), maz@kernel.org wrote: > On Thu, 12 Sep 2019 22:40:34 +0100, > Darius Rad <darius@bluespec.com> wrote: > > Hi Darius, > >> >> As per the existing comment, irq_mask and irq_unmask do not need >> to do anything for the PLIC. However, the functions must exist >> (the pointers cannot be NULL) as they are not optional, based on >> the documentation (Documentation/core-api/genericirq.rst) as well >> as existing usage (e.g., include/linux/irqchip/chained_irq.h). >> >> Signed-off-by: Darius Rad <darius@bluespec.com> >> --- >> drivers/irqchip/irq-sifive-plic.c | 13 +++++++++---- >> 1 file changed, 9 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c >> index cf755964f2f8..52d5169f924f 100644 >> --- a/drivers/irqchip/irq-sifive-plic.c >> +++ b/drivers/irqchip/irq-sifive-plic.c >> @@ -111,6 +111,13 @@ static void plic_irq_disable(struct irq_data *d) >> plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); >> } >> >> +/* >> + * There is no need to mask/unmask PLIC interrupts. They are "masked" >> + * by reading claim and "unmasked" when writing it back. >> + */ >> +static void plic_irq_mask(struct irq_data *d) { } >> +static void plic_irq_unmask(struct irq_data *d) { } > > This outlines a bigger issue. If your irqchip doesn't require > mask/unmask, you're probably not using the right interrupt > flow. Looking at the code, I see you're using handle_simple_irq, which > is almost universally wrong. > > As per the description above, these interrupts should be using the > fasteoi flow, which is designed for this exact behaviour (the > interrupt controller knows which interrupt is in flight and doesn't > require SW to do anything bar signalling the EOI). > > Another thing is that mask/unmask tends to be a requirement, while > enable/disable tends to be optional. There is no hard line here, but > the expectations are that: > > (a) A disabled line can drop interrupts > (b) A masked line cannot drop interrupts > > Depending what the PLIC architecture mandates, you'll need to > implement one and/or the other. Having just (a) is indicative of a HW > bug, and I'm not assuming that this is the case. (b) only is pretty > common, and (a)+(b) has a few adepts. My bet is that it requires (b) > only. > >> + >> #ifdef CONFIG_SMP >> static int plic_set_affinity(struct irq_data *d, >> const struct cpumask *mask_val, bool force) >> @@ -138,12 +145,10 @@ static int plic_set_affinity(struct irq_data *d, >> >> static struct irq_chip plic_chip = { >> .name = "SiFive PLIC", >> - /* >> - * There is no need to mask/unmask PLIC interrupts. They are "masked" >> - * by reading claim and "unmasked" when writing it back. >> - */ >> .irq_enable = plic_irq_enable, >> .irq_disable = plic_irq_disable, >> + .irq_mask = plic_irq_mask, >> + .irq_unmask = plic_irq_unmask, >> #ifdef CONFIG_SMP >> .irq_set_affinity = plic_set_affinity, >> #endif > > Can you give the following patch a go? It brings the irq flow in line > with what the HW can do. It is of course fully untested (not even > compile tested...). > > Thanks, > > M. > > From c0ce33a992ec18f5d3bac7f70de62b1ba2b42090 Mon Sep 17 00:00:00 2001 > From: Marc Zyngier <maz@kernel.org> > Date: Sun, 15 Sep 2019 15:17:45 +0100 > Subject: [PATCH] irqchip/sifive-plic: Switch to fasteoi flow > > The SiFive PLIC interrupt controller seems to have all the HW > features to support the fasteoi flow, but the driver seems to be > stuck in a distant past. Bring it into the 21st century. Thanks. We'd gotten these comments during the review process but nobody had gotten the time to actually fix the issues. > > Signed-off-by: Marc Zyngier <maz@kernel.org> > --- > drivers/irqchip/irq-sifive-plic.c | 29 +++++++++++++++-------------- > 1 file changed, 15 insertions(+), 14 deletions(-) > > diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c > index cf755964f2f8..8fea384d392b 100644 > --- a/drivers/irqchip/irq-sifive-plic.c > +++ b/drivers/irqchip/irq-sifive-plic.c > @@ -97,7 +97,7 @@ static inline void plic_irq_toggle(const struct cpumask *mask, > } > } > > -static void plic_irq_enable(struct irq_data *d) > +static void plic_irq_mask(struct irq_data *d) > { > unsigned int cpu = cpumask_any_and(irq_data_get_affinity_mask(d), > cpu_online_mask); > @@ -106,7 +106,7 @@ static void plic_irq_enable(struct irq_data *d) > plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1); > } > > -static void plic_irq_disable(struct irq_data *d) > +static void plic_irq_unmask(struct irq_data *d) > { > plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); > } > @@ -125,10 +125,8 @@ static int plic_set_affinity(struct irq_data *d, > if (cpu >= nr_cpu_ids) > return -EINVAL; > > - if (!irqd_irq_disabled(d)) { > - plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); > - plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1); > - } > + plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); > + plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1); > > irq_data_update_effective_affinity(d, cpumask_of(cpu)); > > @@ -136,14 +134,18 @@ static int plic_set_affinity(struct irq_data *d, > } > #endif > > +static void plic_irq_eoi(struct irq_data *d) > +{ > + struct plic_handler *handler = this_cpu_ptr(&plic_handlers); > + > + writel(d->hwirq, handler->hart_base + CONTEXT_CLAIM); > +} > + > static struct irq_chip plic_chip = { > .name = "SiFive PLIC", > - /* > - * There is no need to mask/unmask PLIC interrupts. They are "masked" > - * by reading claim and "unmasked" when writing it back. > - */ > - .irq_enable = plic_irq_enable, > - .irq_disable = plic_irq_disable, > + .irq_mask = plic_irq_mask, > + .irq_unmask = plic_irq_unmask, > + .irq_eoi = plic_irq_eoi, > #ifdef CONFIG_SMP > .irq_set_affinity = plic_set_affinity, > #endif > @@ -152,7 +154,7 @@ static struct irq_chip plic_chip = { > static int plic_irqdomain_map(struct irq_domain *d, unsigned int irq, > irq_hw_number_t hwirq) > { > - irq_set_chip_and_handler(irq, &plic_chip, handle_simple_irq); > + irq_set_chip_and_handler(irq, &plic_chip, handle_fasteoi_irq); > irq_set_chip_data(irq, NULL); > irq_set_noprobe(irq); > return 0; > @@ -188,7 +190,6 @@ static void plic_handle_irq(struct pt_regs *regs) > hwirq); > else > generic_handle_irq(irq); > - writel(hwirq, claim); > } > csr_set(sie, SIE_SEIE); > } > -- > 2.20.1 > > > -- > Jazz is not dead, it just smells funny. Reviewed-by: Palmer Dabbelt <palmer@sifive.com> Tested-by: Palmer Dabbelt <palmer@sifive.com> (QEMU Boot) We should test them on the hardware, but I don't have any with me right now. David's probably in the best spot to do this, as he's got a setup that does all the weird interrupt sources (ie, PCIe). David: do you mind testing this? I've put the patch here: ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/palmer/linux.git -b plic-fasteoi
On Sun, 15 Sep 2019 18:31:33 +0100, Palmer Dabbelt <palmer@sifive.com> wrote: Hi Palmer, > > On Sun, 15 Sep 2019 07:24:20 PDT (-0700), maz@kernel.org wrote: > > On Thu, 12 Sep 2019 22:40:34 +0100, > > Darius Rad <darius@bluespec.com> wrote: > > > > Hi Darius, > > > >> > >> As per the existing comment, irq_mask and irq_unmask do not need > >> to do anything for the PLIC. However, the functions must exist > >> (the pointers cannot be NULL) as they are not optional, based on > >> the documentation (Documentation/core-api/genericirq.rst) as well > >> as existing usage (e.g., include/linux/irqchip/chained_irq.h). > >> > >> Signed-off-by: Darius Rad <darius@bluespec.com> > >> --- > >> drivers/irqchip/irq-sifive-plic.c | 13 +++++++++---- > >> 1 file changed, 9 insertions(+), 4 deletions(-) > >> > >> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c > >> index cf755964f2f8..52d5169f924f 100644 > >> --- a/drivers/irqchip/irq-sifive-plic.c > >> +++ b/drivers/irqchip/irq-sifive-plic.c > >> @@ -111,6 +111,13 @@ static void plic_irq_disable(struct irq_data *d) > >> plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); > >> } > >> +/* > >> + * There is no need to mask/unmask PLIC interrupts. They are "masked" > >> + * by reading claim and "unmasked" when writing it back. > >> + */ > >> +static void plic_irq_mask(struct irq_data *d) { } > >> +static void plic_irq_unmask(struct irq_data *d) { } > > > > This outlines a bigger issue. If your irqchip doesn't require > > mask/unmask, you're probably not using the right interrupt > > flow. Looking at the code, I see you're using handle_simple_irq, which > > is almost universally wrong. > > > > As per the description above, these interrupts should be using the > > fasteoi flow, which is designed for this exact behaviour (the > > interrupt controller knows which interrupt is in flight and doesn't > > require SW to do anything bar signalling the EOI). > > > > Another thing is that mask/unmask tends to be a requirement, while > > enable/disable tends to be optional. There is no hard line here, but > > the expectations are that: > > > > (a) A disabled line can drop interrupts > > (b) A masked line cannot drop interrupts > > > > Depending what the PLIC architecture mandates, you'll need to > > implement one and/or the other. Having just (a) is indicative of a HW > > bug, and I'm not assuming that this is the case. (b) only is pretty > > common, and (a)+(b) has a few adepts. My bet is that it requires (b) > > only. > > > >> + > >> #ifdef CONFIG_SMP > >> static int plic_set_affinity(struct irq_data *d, > >> const struct cpumask *mask_val, bool force) > >> @@ -138,12 +145,10 @@ static int plic_set_affinity(struct irq_data *d, > >> static struct irq_chip plic_chip = { > >> .name = "SiFive PLIC", > >> - /* > >> - * There is no need to mask/unmask PLIC interrupts. They are "masked" > >> - * by reading claim and "unmasked" when writing it back. > >> - */ > >> .irq_enable = plic_irq_enable, > >> .irq_disable = plic_irq_disable, > >> + .irq_mask = plic_irq_mask, > >> + .irq_unmask = plic_irq_unmask, > >> #ifdef CONFIG_SMP > >> .irq_set_affinity = plic_set_affinity, > >> #endif > > > > Can you give the following patch a go? It brings the irq flow in line > > with what the HW can do. It is of course fully untested (not even > > compile tested...). > > > > Thanks, > > > > M. > > > > From c0ce33a992ec18f5d3bac7f70de62b1ba2b42090 Mon Sep 17 00:00:00 2001 > > From: Marc Zyngier <maz@kernel.org> > > Date: Sun, 15 Sep 2019 15:17:45 +0100 > > Subject: [PATCH] irqchip/sifive-plic: Switch to fasteoi flow > > > > The SiFive PLIC interrupt controller seems to have all the HW > > features to support the fasteoi flow, but the driver seems to be > > stuck in a distant past. Bring it into the 21st century. > > Thanks. We'd gotten these comments during the review process but > nobody had gotten the time to actually fix the issues. No worries. The IRQ subsystem is an acquired taste... ;-) > > > > Signed-off-by: Marc Zyngier <maz@kernel.org> > > --- > > drivers/irqchip/irq-sifive-plic.c | 29 +++++++++++++++-------------- > > 1 file changed, 15 insertions(+), 14 deletions(-) > > > > diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c > > index cf755964f2f8..8fea384d392b 100644 > > --- a/drivers/irqchip/irq-sifive-plic.c > > +++ b/drivers/irqchip/irq-sifive-plic.c > > @@ -97,7 +97,7 @@ static inline void plic_irq_toggle(const struct cpumask *mask, > > } > > } > > -static void plic_irq_enable(struct irq_data *d) > > +static void plic_irq_mask(struct irq_data *d) Of course, this is wrong. The perks of trying to do something at the last minute while boarding an airplane. Don't do that. This should of course read "plic_irq_unmask"... > > { > > unsigned int cpu = cpumask_any_and(irq_data_get_affinity_mask(d), > > cpu_online_mask); > > @@ -106,7 +106,7 @@ static void plic_irq_enable(struct irq_data *d) > > plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1); > > } > > -static void plic_irq_disable(struct irq_data *d) > > +static void plic_irq_unmask(struct irq_data *d) ... and this should be "plic_irq_mask". [...] > Reviewed-by: Palmer Dabbelt <palmer@sifive.com> > Tested-by: Palmer Dabbelt <palmer@sifive.com> (QEMU Boot) Huhuh... It may be that QEMU doesn't implement the full-fat PLIC, as the above bug should have kept the IRQ lines masked. > We should test them on the hardware, but I don't have any with me > right now. David's probably in the best spot to do this, as he's got > a setup that does all the weird interrupt sources (ie, PCIe). > > David: do you mind testing this? I've put the patch here: > > ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/palmer/linux.git > -b plic-fasteoi I've pushed out a branch with the fixed patch: git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git irq/plic-fasteoi Thanks, M.
On Sun, 15 Sep 2019 11:20:40 PDT (-0700), maz@kernel.org wrote: > On Sun, 15 Sep 2019 18:31:33 +0100, > Palmer Dabbelt <palmer@sifive.com> wrote: > > Hi Palmer, > >> >> On Sun, 15 Sep 2019 07:24:20 PDT (-0700), maz@kernel.org wrote: >> > On Thu, 12 Sep 2019 22:40:34 +0100, >> > Darius Rad <darius@bluespec.com> wrote: >> > >> > Hi Darius, >> > >> >> >> >> As per the existing comment, irq_mask and irq_unmask do not need >> >> to do anything for the PLIC. However, the functions must exist >> >> (the pointers cannot be NULL) as they are not optional, based on >> >> the documentation (Documentation/core-api/genericirq.rst) as well >> >> as existing usage (e.g., include/linux/irqchip/chained_irq.h). >> >> >> >> Signed-off-by: Darius Rad <darius@bluespec.com> >> >> --- >> >> drivers/irqchip/irq-sifive-plic.c | 13 +++++++++---- >> >> 1 file changed, 9 insertions(+), 4 deletions(-) >> >> >> >> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c >> >> index cf755964f2f8..52d5169f924f 100644 >> >> --- a/drivers/irqchip/irq-sifive-plic.c >> >> +++ b/drivers/irqchip/irq-sifive-plic.c >> >> @@ -111,6 +111,13 @@ static void plic_irq_disable(struct irq_data *d) >> >> plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); >> >> } >> >> +/* >> >> + * There is no need to mask/unmask PLIC interrupts. They are "masked" >> >> + * by reading claim and "unmasked" when writing it back. >> >> + */ >> >> +static void plic_irq_mask(struct irq_data *d) { } >> >> +static void plic_irq_unmask(struct irq_data *d) { } >> > >> > This outlines a bigger issue. If your irqchip doesn't require >> > mask/unmask, you're probably not using the right interrupt >> > flow. Looking at the code, I see you're using handle_simple_irq, which >> > is almost universally wrong. >> > >> > As per the description above, these interrupts should be using the >> > fasteoi flow, which is designed for this exact behaviour (the >> > interrupt controller knows which interrupt is in flight and doesn't >> > require SW to do anything bar signalling the EOI). >> > >> > Another thing is that mask/unmask tends to be a requirement, while >> > enable/disable tends to be optional. There is no hard line here, but >> > the expectations are that: >> > >> > (a) A disabled line can drop interrupts >> > (b) A masked line cannot drop interrupts >> > >> > Depending what the PLIC architecture mandates, you'll need to >> > implement one and/or the other. Having just (a) is indicative of a HW >> > bug, and I'm not assuming that this is the case. (b) only is pretty >> > common, and (a)+(b) has a few adepts. My bet is that it requires (b) >> > only. >> > >> >> + >> >> #ifdef CONFIG_SMP >> >> static int plic_set_affinity(struct irq_data *d, >> >> const struct cpumask *mask_val, bool force) >> >> @@ -138,12 +145,10 @@ static int plic_set_affinity(struct irq_data *d, >> >> static struct irq_chip plic_chip = { >> >> .name = "SiFive PLIC", >> >> - /* >> >> - * There is no need to mask/unmask PLIC interrupts. They are "masked" >> >> - * by reading claim and "unmasked" when writing it back. >> >> - */ >> >> .irq_enable = plic_irq_enable, >> >> .irq_disable = plic_irq_disable, >> >> + .irq_mask = plic_irq_mask, >> >> + .irq_unmask = plic_irq_unmask, >> >> #ifdef CONFIG_SMP >> >> .irq_set_affinity = plic_set_affinity, >> >> #endif >> > >> > Can you give the following patch a go? It brings the irq flow in line >> > with what the HW can do. It is of course fully untested (not even >> > compile tested...). >> > >> > Thanks, >> > >> > M. >> > >> > From c0ce33a992ec18f5d3bac7f70de62b1ba2b42090 Mon Sep 17 00:00:00 2001 >> > From: Marc Zyngier <maz@kernel.org> >> > Date: Sun, 15 Sep 2019 15:17:45 +0100 >> > Subject: [PATCH] irqchip/sifive-plic: Switch to fasteoi flow >> > >> > The SiFive PLIC interrupt controller seems to have all the HW >> > features to support the fasteoi flow, but the driver seems to be >> > stuck in a distant past. Bring it into the 21st century. >> >> Thanks. We'd gotten these comments during the review process but >> nobody had gotten the time to actually fix the issues. > > No worries. The IRQ subsystem is an acquired taste... ;-) > >> > >> > Signed-off-by: Marc Zyngier <maz@kernel.org> >> > --- >> > drivers/irqchip/irq-sifive-plic.c | 29 +++++++++++++++-------------- >> > 1 file changed, 15 insertions(+), 14 deletions(-) >> > >> > diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c >> > index cf755964f2f8..8fea384d392b 100644 >> > --- a/drivers/irqchip/irq-sifive-plic.c >> > +++ b/drivers/irqchip/irq-sifive-plic.c >> > @@ -97,7 +97,7 @@ static inline void plic_irq_toggle(const struct cpumask *mask, >> > } >> > } >> > -static void plic_irq_enable(struct irq_data *d) >> > +static void plic_irq_mask(struct irq_data *d) > > Of course, this is wrong. The perks of trying to do something at the > last minute while boarding an airplane. Don't do that. > > This should of course read "plic_irq_unmask"... > >> > { >> > unsigned int cpu = cpumask_any_and(irq_data_get_affinity_mask(d), >> > cpu_online_mask); >> > @@ -106,7 +106,7 @@ static void plic_irq_enable(struct irq_data *d) >> > plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1); >> > } >> > -static void plic_irq_disable(struct irq_data *d) >> > +static void plic_irq_unmask(struct irq_data *d) > > ... and this should be "plic_irq_mask". > > [...] > >> Reviewed-by: Palmer Dabbelt <palmer@sifive.com> >> Tested-by: Palmer Dabbelt <palmer@sifive.com> (QEMU Boot) > > Huhuh... It may be that QEMU doesn't implement the full-fat PLIC, as > the above bug should have kept the IRQ lines masked. Yep, looks like the PLIC implementation in QEMU is nonsense. That needs to be rewritten, and this needs to be tested on hardware. >> We should test them on the hardware, but I don't have any with me >> right now. David's probably in the best spot to do this, as he's got >> a setup that does all the weird interrupt sources (ie, PCIe). >> >> David: do you mind testing this? I've put the patch here: >> >> ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/palmer/linux.git >> -b plic-fasteoi > > I've pushed out a branch with the fixed patch: > > git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git irq/plic-fasteoi > > Thanks, > > M.
On 9/15/19 2:20 PM, Marc Zyngier wrote: > On Sun, 15 Sep 2019 18:31:33 +0100, > Palmer Dabbelt <palmer@sifive.com> wrote: > > Hi Palmer, > >> >> On Sun, 15 Sep 2019 07:24:20 PDT (-0700), maz@kernel.org wrote: >>> On Thu, 12 Sep 2019 22:40:34 +0100, >>> Darius Rad <darius@bluespec.com> wrote: >>> >>> Hi Darius, >>> >>>> >>>> As per the existing comment, irq_mask and irq_unmask do not need >>>> to do anything for the PLIC. However, the functions must exist >>>> (the pointers cannot be NULL) as they are not optional, based on >>>> the documentation (Documentation/core-api/genericirq.rst) as well >>>> as existing usage (e.g., include/linux/irqchip/chained_irq.h). >>>> >>>> Signed-off-by: Darius Rad <darius@bluespec.com> >>>> --- >>>> drivers/irqchip/irq-sifive-plic.c | 13 +++++++++---- >>>> 1 file changed, 9 insertions(+), 4 deletions(-) >>>> >>>> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c >>>> index cf755964f2f8..52d5169f924f 100644 >>>> --- a/drivers/irqchip/irq-sifive-plic.c >>>> +++ b/drivers/irqchip/irq-sifive-plic.c >>>> @@ -111,6 +111,13 @@ static void plic_irq_disable(struct irq_data *d) >>>> plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); >>>> } >>>> +/* >>>> + * There is no need to mask/unmask PLIC interrupts. They are "masked" >>>> + * by reading claim and "unmasked" when writing it back. >>>> + */ >>>> +static void plic_irq_mask(struct irq_data *d) { } >>>> +static void plic_irq_unmask(struct irq_data *d) { } >>> >>> This outlines a bigger issue. If your irqchip doesn't require >>> mask/unmask, you're probably not using the right interrupt >>> flow. Looking at the code, I see you're using handle_simple_irq, which >>> is almost universally wrong. >>> >>> As per the description above, these interrupts should be using the >>> fasteoi flow, which is designed for this exact behaviour (the >>> interrupt controller knows which interrupt is in flight and doesn't >>> require SW to do anything bar signalling the EOI). >>> >>> Another thing is that mask/unmask tends to be a requirement, while >>> enable/disable tends to be optional. There is no hard line here, but >>> the expectations are that: >>> >>> (a) A disabled line can drop interrupts >>> (b) A masked line cannot drop interrupts >>> >>> Depending what the PLIC architecture mandates, you'll need to >>> implement one and/or the other. Having just (a) is indicative of a HW >>> bug, and I'm not assuming that this is the case. (b) only is pretty >>> common, and (a)+(b) has a few adepts. My bet is that it requires (b) >>> only. >>> >>>> + >>>> #ifdef CONFIG_SMP >>>> static int plic_set_affinity(struct irq_data *d, >>>> const struct cpumask *mask_val, bool force) >>>> @@ -138,12 +145,10 @@ static int plic_set_affinity(struct irq_data *d, >>>> static struct irq_chip plic_chip = { >>>> .name = "SiFive PLIC", >>>> - /* >>>> - * There is no need to mask/unmask PLIC interrupts. They are "masked" >>>> - * by reading claim and "unmasked" when writing it back. >>>> - */ >>>> .irq_enable = plic_irq_enable, >>>> .irq_disable = plic_irq_disable, >>>> + .irq_mask = plic_irq_mask, >>>> + .irq_unmask = plic_irq_unmask, >>>> #ifdef CONFIG_SMP >>>> .irq_set_affinity = plic_set_affinity, >>>> #endif >>> >>> Can you give the following patch a go? It brings the irq flow in line >>> with what the HW can do. It is of course fully untested (not even >>> compile tested...). >>> >>> Thanks, >>> >>> M. >>> >>> From c0ce33a992ec18f5d3bac7f70de62b1ba2b42090 Mon Sep 17 00:00:00 2001 >>> From: Marc Zyngier <maz@kernel.org> >>> Date: Sun, 15 Sep 2019 15:17:45 +0100 >>> Subject: [PATCH] irqchip/sifive-plic: Switch to fasteoi flow >>> >>> The SiFive PLIC interrupt controller seems to have all the HW >>> features to support the fasteoi flow, but the driver seems to be >>> stuck in a distant past. Bring it into the 21st century. >> >> Thanks. We'd gotten these comments during the review process but >> nobody had gotten the time to actually fix the issues. > > No worries. The IRQ subsystem is an acquired taste... ;-) > >>> >>> Signed-off-by: Marc Zyngier <maz@kernel.org> >>> --- >>> drivers/irqchip/irq-sifive-plic.c | 29 +++++++++++++++-------------- >>> 1 file changed, 15 insertions(+), 14 deletions(-) >>> >>> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c >>> index cf755964f2f8..8fea384d392b 100644 >>> --- a/drivers/irqchip/irq-sifive-plic.c >>> +++ b/drivers/irqchip/irq-sifive-plic.c >>> @@ -97,7 +97,7 @@ static inline void plic_irq_toggle(const struct cpumask *mask, >>> } >>> } >>> -static void plic_irq_enable(struct irq_data *d) >>> +static void plic_irq_mask(struct irq_data *d) > > Of course, this is wrong. The perks of trying to do something at the > last minute while boarding an airplane. Don't do that. > > This should of course read "plic_irq_unmask"... > >>> { >>> unsigned int cpu = cpumask_any_and(irq_data_get_affinity_mask(d), >>> cpu_online_mask); >>> @@ -106,7 +106,7 @@ static void plic_irq_enable(struct irq_data *d) >>> plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1); >>> } >>> -static void plic_irq_disable(struct irq_data *d) >>> +static void plic_irq_unmask(struct irq_data *d) > > ... and this should be "plic_irq_mask". > > [...] > >> Reviewed-by: Palmer Dabbelt <palmer@sifive.com> >> Tested-by: Palmer Dabbelt <palmer@sifive.com> (QEMU Boot) > > Huhuh... It may be that QEMU doesn't implement the full-fat PLIC, as > the above bug should have kept the IRQ lines masked. > >> We should test them on the hardware, but I don't have any with me >> right now. David's probably in the best spot to do this, as he's got >> a setup that does all the weird interrupt sources (ie, PCIe). >> >> David: do you mind testing this? I've put the patch here: >> >> ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/palmer/linux.git >> -b plic-fasteoi > > I've pushed out a branch with the fixed patch: > > git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git irq/plic-fasteoi > That patch works for me on real-ish hardware. I tried on two FPGA systems that have different PLIC implementations. Both include a PCIe root port (and associated interrupt source). So for whatever it's worth: Tested-by: Darius Rad <darius@bluespec.com> > Thanks, > > M. >
On Mon, 16 Sep 2019 12:04:56 PDT (-0700), Darius Rad wrote: > On 9/15/19 2:20 PM, Marc Zyngier wrote: >> On Sun, 15 Sep 2019 18:31:33 +0100, >> Palmer Dabbelt <palmer@sifive.com> wrote: >> >> Hi Palmer, >> >>> >>> On Sun, 15 Sep 2019 07:24:20 PDT (-0700), maz@kernel.org wrote: >>>> On Thu, 12 Sep 2019 22:40:34 +0100, >>>> Darius Rad <darius@bluespec.com> wrote: >>>> >>>> Hi Darius, >>>> >>>>> >>>>> As per the existing comment, irq_mask and irq_unmask do not need >>>>> to do anything for the PLIC. However, the functions must exist >>>>> (the pointers cannot be NULL) as they are not optional, based on >>>>> the documentation (Documentation/core-api/genericirq.rst) as well >>>>> as existing usage (e.g., include/linux/irqchip/chained_irq.h). >>>>> >>>>> Signed-off-by: Darius Rad <darius@bluespec.com> >>>>> --- >>>>> drivers/irqchip/irq-sifive-plic.c | 13 +++++++++---- >>>>> 1 file changed, 9 insertions(+), 4 deletions(-) >>>>> >>>>> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c >>>>> index cf755964f2f8..52d5169f924f 100644 >>>>> --- a/drivers/irqchip/irq-sifive-plic.c >>>>> +++ b/drivers/irqchip/irq-sifive-plic.c >>>>> @@ -111,6 +111,13 @@ static void plic_irq_disable(struct irq_data *d) >>>>> plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); >>>>> } >>>>> +/* >>>>> + * There is no need to mask/unmask PLIC interrupts. They are "masked" >>>>> + * by reading claim and "unmasked" when writing it back. >>>>> + */ >>>>> +static void plic_irq_mask(struct irq_data *d) { } >>>>> +static void plic_irq_unmask(struct irq_data *d) { } >>>> >>>> This outlines a bigger issue. If your irqchip doesn't require >>>> mask/unmask, you're probably not using the right interrupt >>>> flow. Looking at the code, I see you're using handle_simple_irq, which >>>> is almost universally wrong. >>>> >>>> As per the description above, these interrupts should be using the >>>> fasteoi flow, which is designed for this exact behaviour (the >>>> interrupt controller knows which interrupt is in flight and doesn't >>>> require SW to do anything bar signalling the EOI). >>>> >>>> Another thing is that mask/unmask tends to be a requirement, while >>>> enable/disable tends to be optional. There is no hard line here, but >>>> the expectations are that: >>>> >>>> (a) A disabled line can drop interrupts >>>> (b) A masked line cannot drop interrupts >>>> >>>> Depending what the PLIC architecture mandates, you'll need to >>>> implement one and/or the other. Having just (a) is indicative of a HW >>>> bug, and I'm not assuming that this is the case. (b) only is pretty >>>> common, and (a)+(b) has a few adepts. My bet is that it requires (b) >>>> only. >>>> >>>>> + >>>>> #ifdef CONFIG_SMP >>>>> static int plic_set_affinity(struct irq_data *d, >>>>> const struct cpumask *mask_val, bool force) >>>>> @@ -138,12 +145,10 @@ static int plic_set_affinity(struct irq_data *d, >>>>> static struct irq_chip plic_chip = { >>>>> .name = "SiFive PLIC", >>>>> - /* >>>>> - * There is no need to mask/unmask PLIC interrupts. They are "masked" >>>>> - * by reading claim and "unmasked" when writing it back. >>>>> - */ >>>>> .irq_enable = plic_irq_enable, >>>>> .irq_disable = plic_irq_disable, >>>>> + .irq_mask = plic_irq_mask, >>>>> + .irq_unmask = plic_irq_unmask, >>>>> #ifdef CONFIG_SMP >>>>> .irq_set_affinity = plic_set_affinity, >>>>> #endif >>>> >>>> Can you give the following patch a go? It brings the irq flow in line >>>> with what the HW can do. It is of course fully untested (not even >>>> compile tested...). >>>> >>>> Thanks, >>>> >>>> M. >>>> >>>> From c0ce33a992ec18f5d3bac7f70de62b1ba2b42090 Mon Sep 17 00:00:00 2001 >>>> From: Marc Zyngier <maz@kernel.org> >>>> Date: Sun, 15 Sep 2019 15:17:45 +0100 >>>> Subject: [PATCH] irqchip/sifive-plic: Switch to fasteoi flow >>>> >>>> The SiFive PLIC interrupt controller seems to have all the HW >>>> features to support the fasteoi flow, but the driver seems to be >>>> stuck in a distant past. Bring it into the 21st century. >>> >>> Thanks. We'd gotten these comments during the review process but >>> nobody had gotten the time to actually fix the issues. >> >> No worries. The IRQ subsystem is an acquired taste... ;-) >> >>>> >>>> Signed-off-by: Marc Zyngier <maz@kernel.org> >>>> --- >>>> drivers/irqchip/irq-sifive-plic.c | 29 +++++++++++++++-------------- >>>> 1 file changed, 15 insertions(+), 14 deletions(-) >>>> >>>> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c >>>> index cf755964f2f8..8fea384d392b 100644 >>>> --- a/drivers/irqchip/irq-sifive-plic.c >>>> +++ b/drivers/irqchip/irq-sifive-plic.c >>>> @@ -97,7 +97,7 @@ static inline void plic_irq_toggle(const struct cpumask *mask, >>>> } >>>> } >>>> -static void plic_irq_enable(struct irq_data *d) >>>> +static void plic_irq_mask(struct irq_data *d) >> >> Of course, this is wrong. The perks of trying to do something at the >> last minute while boarding an airplane. Don't do that. >> >> This should of course read "plic_irq_unmask"... >> >>>> { >>>> unsigned int cpu = cpumask_any_and(irq_data_get_affinity_mask(d), >>>> cpu_online_mask); >>>> @@ -106,7 +106,7 @@ static void plic_irq_enable(struct irq_data *d) >>>> plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1); >>>> } >>>> -static void plic_irq_disable(struct irq_data *d) >>>> +static void plic_irq_unmask(struct irq_data *d) >> >> ... and this should be "plic_irq_mask". >> >> [...] >> >>> Reviewed-by: Palmer Dabbelt <palmer@sifive.com> >>> Tested-by: Palmer Dabbelt <palmer@sifive.com> (QEMU Boot) >> >> Huhuh... It may be that QEMU doesn't implement the full-fat PLIC, as >> the above bug should have kept the IRQ lines masked. >> >>> We should test them on the hardware, but I don't have any with me >>> right now. David's probably in the best spot to do this, as he's got >>> a setup that does all the weird interrupt sources (ie, PCIe). >>> >>> David: do you mind testing this? I've put the patch here: >>> >>> ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/palmer/linux.git >>> -b plic-fasteoi >> >> I've pushed out a branch with the fixed patch: >> >> git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git irq/plic-fasteoi >> > > That patch works for me on real-ish hardware. I tried on two FPGA > systems that have different PLIC implementations. Both include > a PCIe root port (and associated interrupt source). So for > whatever it's worth: > > Tested-by: Darius Rad <darius@bluespec.com> Awesome, thanks. Would it be OK to put a "(on two hardware PLIC implementations)" after that, just so we're clear as to who tested what? Assuming one of yours wasn't a SiFive PLIC then it'd be great if David could still give this a whack, but I don't think it strictly needs to block merging the patch. I've included the right David this time, with any luck that will be more fruitful :) > >> Thanks, >> >> M. >>
On Mon, 16 Sep 2019 13:51:58 -0700 (PDT) Palmer Dabbelt <palmer@sifive.com> wrote: > On Mon, 16 Sep 2019 12:04:56 PDT (-0700), Darius Rad wrote: > > On 9/15/19 2:20 PM, Marc Zyngier wrote: > >> On Sun, 15 Sep 2019 18:31:33 +0100, > >> Palmer Dabbelt <palmer@sifive.com> wrote: > >> > >> Hi Palmer, > >> > >>> > >>> On Sun, 15 Sep 2019 07:24:20 PDT (-0700), maz@kernel.org wrote: > >>>> On Thu, 12 Sep 2019 22:40:34 +0100, > >>>> Darius Rad <darius@bluespec.com> wrote: > >>>> > >>>> Hi Darius, > >>>> > >>>>> > >>>>> As per the existing comment, irq_mask and irq_unmask do not need > >>>>> to do anything for the PLIC. However, the functions must exist > >>>>> (the pointers cannot be NULL) as they are not optional, based on > >>>>> the documentation (Documentation/core-api/genericirq.rst) as well > >>>>> as existing usage (e.g., include/linux/irqchip/chained_irq.h). > >>>>> > >>>>> Signed-off-by: Darius Rad <darius@bluespec.com> > >>>>> --- > >>>>> drivers/irqchip/irq-sifive-plic.c | 13 +++++++++---- > >>>>> 1 file changed, 9 insertions(+), 4 deletions(-) > >>>>> > >>>>> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c > >>>>> index cf755964f2f8..52d5169f924f 100644 > >>>>> --- a/drivers/irqchip/irq-sifive-plic.c > >>>>> +++ b/drivers/irqchip/irq-sifive-plic.c > >>>>> @@ -111,6 +111,13 @@ static void plic_irq_disable(struct irq_data *d) > >>>>> plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); > >>>>> } > >>>>> +/* > >>>>> + * There is no need to mask/unmask PLIC interrupts. They are "masked" > >>>>> + * by reading claim and "unmasked" when writing it back. > >>>>> + */ > >>>>> +static void plic_irq_mask(struct irq_data *d) { } > >>>>> +static void plic_irq_unmask(struct irq_data *d) { } > >>>> > >>>> This outlines a bigger issue. If your irqchip doesn't require > >>>> mask/unmask, you're probably not using the right interrupt > >>>> flow. Looking at the code, I see you're using handle_simple_irq, which > >>>> is almost universally wrong. > >>>> > >>>> As per the description above, these interrupts should be using the > >>>> fasteoi flow, which is designed for this exact behaviour (the > >>>> interrupt controller knows which interrupt is in flight and doesn't > >>>> require SW to do anything bar signalling the EOI). > >>>> > >>>> Another thing is that mask/unmask tends to be a requirement, while > >>>> enable/disable tends to be optional. There is no hard line here, but > >>>> the expectations are that: > >>>> > >>>> (a) A disabled line can drop interrupts > >>>> (b) A masked line cannot drop interrupts > >>>> > >>>> Depending what the PLIC architecture mandates, you'll need to > >>>> implement one and/or the other. Having just (a) is indicative of a HW > >>>> bug, and I'm not assuming that this is the case. (b) only is pretty > >>>> common, and (a)+(b) has a few adepts. My bet is that it requires (b) > >>>> only. > >>>> > >>>>> + > >>>>> #ifdef CONFIG_SMP > >>>>> static int plic_set_affinity(struct irq_data *d, > >>>>> const struct cpumask *mask_val, bool force) > >>>>> @@ -138,12 +145,10 @@ static int plic_set_affinity(struct irq_data *d, > >>>>> static struct irq_chip plic_chip = { > >>>>> .name = "SiFive PLIC", > >>>>> - /* > >>>>> - * There is no need to mask/unmask PLIC interrupts. They are "masked" > >>>>> - * by reading claim and "unmasked" when writing it back. > >>>>> - */ > >>>>> .irq_enable = plic_irq_enable, > >>>>> .irq_disable = plic_irq_disable, > >>>>> + .irq_mask = plic_irq_mask, > >>>>> + .irq_unmask = plic_irq_unmask, > >>>>> #ifdef CONFIG_SMP > >>>>> .irq_set_affinity = plic_set_affinity, > >>>>> #endif > >>>> > >>>> Can you give the following patch a go? It brings the irq flow in line > >>>> with what the HW can do. It is of course fully untested (not even > >>>> compile tested...). > >>>> > >>>> Thanks, > >>>> > >>>> M. > >>>> > >>>> From c0ce33a992ec18f5d3bac7f70de62b1ba2b42090 Mon Sep 17 00:00:00 2001 > >>>> From: Marc Zyngier <maz@kernel.org> > >>>> Date: Sun, 15 Sep 2019 15:17:45 +0100 > >>>> Subject: [PATCH] irqchip/sifive-plic: Switch to fasteoi flow > >>>> > >>>> The SiFive PLIC interrupt controller seems to have all the HW > >>>> features to support the fasteoi flow, but the driver seems to be > >>>> stuck in a distant past. Bring it into the 21st century. > >>> > >>> Thanks. We'd gotten these comments during the review process but > >>> nobody had gotten the time to actually fix the issues. > >> > >> No worries. The IRQ subsystem is an acquired taste... ;-) > >> > >>>> > >>>> Signed-off-by: Marc Zyngier <maz@kernel.org> > >>>> --- > >>>> drivers/irqchip/irq-sifive-plic.c | 29 +++++++++++++++-------------- > >>>> 1 file changed, 15 insertions(+), 14 deletions(-) > >>>> > >>>> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c > >>>> index cf755964f2f8..8fea384d392b 100644 > >>>> --- a/drivers/irqchip/irq-sifive-plic.c > >>>> +++ b/drivers/irqchip/irq-sifive-plic.c > >>>> @@ -97,7 +97,7 @@ static inline void plic_irq_toggle(const struct cpumask *mask, > >>>> } > >>>> } > >>>> -static void plic_irq_enable(struct irq_data *d) > >>>> +static void plic_irq_mask(struct irq_data *d) > >> > >> Of course, this is wrong. The perks of trying to do something at the > >> last minute while boarding an airplane. Don't do that. > >> > >> This should of course read "plic_irq_unmask"... > >> > >>>> { > >>>> unsigned int cpu = cpumask_any_and(irq_data_get_affinity_mask(d), > >>>> cpu_online_mask); > >>>> @@ -106,7 +106,7 @@ static void plic_irq_enable(struct irq_data *d) > >>>> plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1); > >>>> } > >>>> -static void plic_irq_disable(struct irq_data *d) > >>>> +static void plic_irq_unmask(struct irq_data *d) > >> > >> ... and this should be "plic_irq_mask". > >> > >> [...] > >> > >>> Reviewed-by: Palmer Dabbelt <palmer@sifive.com> > >>> Tested-by: Palmer Dabbelt <palmer@sifive.com> (QEMU Boot) > >> > >> Huhuh... It may be that QEMU doesn't implement the full-fat PLIC, as > >> the above bug should have kept the IRQ lines masked. > >> > >>> We should test them on the hardware, but I don't have any with me > >>> right now. David's probably in the best spot to do this, as he's got > >>> a setup that does all the weird interrupt sources (ie, PCIe). > >>> > >>> David: do you mind testing this? I've put the patch here: > >>> > >>> ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/palmer/linux.git > >>> -b plic-fasteoi > >> > >> I've pushed out a branch with the fixed patch: > >> > >> git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git irq/plic-fasteoi > >> > > > > That patch works for me on real-ish hardware. I tried on two FPGA > > systems that have different PLIC implementations. Both include > > a PCIe root port (and associated interrupt source). So for > > whatever it's worth: > > > > Tested-by: Darius Rad <darius@bluespec.com> > > Awesome, thanks. Would it be OK to put a "(on two hardware PLIC > implementations)" after that, just so we're clear as to who tested > what? Sure, no problem. > Assuming one of yours wasn't a SiFive PLIC then it'd be great if > David could still give this a whack, but I don't think it strictly > needs to block merging the patch. I've included the right David this > time, with any luck that will be more fruitful :) Well, we still have time before -rc1. Once David gets a chance to test it, I'll apply it. Additional question: do you want this backported to -stable? If so, how far? Thanks, M.
On 9/16/19 4:51 PM, Palmer Dabbelt wrote: > On Mon, 16 Sep 2019 12:04:56 PDT (-0700), Darius Rad wrote: >> On 9/15/19 2:20 PM, Marc Zyngier wrote: >>> On Sun, 15 Sep 2019 18:31:33 +0100, >>> Palmer Dabbelt <palmer@sifive.com> wrote: >>> >>> Hi Palmer, >>> >>>> >>>> On Sun, 15 Sep 2019 07:24:20 PDT (-0700), maz@kernel.org wrote: >>>>> On Thu, 12 Sep 2019 22:40:34 +0100, >>>>> Darius Rad <darius@bluespec.com> wrote: >>>>> >>>>> Hi Darius, >>>>> >>>>>> >>>>>> As per the existing comment, irq_mask and irq_unmask do not need >>>>>> to do anything for the PLIC. However, the functions must exist >>>>>> (the pointers cannot be NULL) as they are not optional, based on >>>>>> the documentation (Documentation/core-api/genericirq.rst) as well >>>>>> as existing usage (e.g., include/linux/irqchip/chained_irq.h). >>>>>> >>>>>> Signed-off-by: Darius Rad <darius@bluespec.com> >>>>>> --- >>>>>> drivers/irqchip/irq-sifive-plic.c | 13 +++++++++---- >>>>>> 1 file changed, 9 insertions(+), 4 deletions(-) >>>>>> >>>>>> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c >>>>>> index cf755964f2f8..52d5169f924f 100644 >>>>>> --- a/drivers/irqchip/irq-sifive-plic.c >>>>>> +++ b/drivers/irqchip/irq-sifive-plic.c >>>>>> @@ -111,6 +111,13 @@ static void plic_irq_disable(struct irq_data *d) >>>>>> plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); >>>>>> } >>>>>> +/* >>>>>> + * There is no need to mask/unmask PLIC interrupts. They are "masked" >>>>>> + * by reading claim and "unmasked" when writing it back. >>>>>> + */ >>>>>> +static void plic_irq_mask(struct irq_data *d) { } >>>>>> +static void plic_irq_unmask(struct irq_data *d) { } >>>>> >>>>> This outlines a bigger issue. If your irqchip doesn't require >>>>> mask/unmask, you're probably not using the right interrupt >>>>> flow. Looking at the code, I see you're using handle_simple_irq, which >>>>> is almost universally wrong. >>>>> >>>>> As per the description above, these interrupts should be using the >>>>> fasteoi flow, which is designed for this exact behaviour (the >>>>> interrupt controller knows which interrupt is in flight and doesn't >>>>> require SW to do anything bar signalling the EOI). >>>>> >>>>> Another thing is that mask/unmask tends to be a requirement, while >>>>> enable/disable tends to be optional. There is no hard line here, but >>>>> the expectations are that: >>>>> >>>>> (a) A disabled line can drop interrupts >>>>> (b) A masked line cannot drop interrupts >>>>> >>>>> Depending what the PLIC architecture mandates, you'll need to >>>>> implement one and/or the other. Having just (a) is indicative of a HW >>>>> bug, and I'm not assuming that this is the case. (b) only is pretty >>>>> common, and (a)+(b) has a few adepts. My bet is that it requires (b) >>>>> only. >>>>> >>>>>> + >>>>>> #ifdef CONFIG_SMP >>>>>> static int plic_set_affinity(struct irq_data *d, >>>>>> const struct cpumask *mask_val, bool force) >>>>>> @@ -138,12 +145,10 @@ static int plic_set_affinity(struct irq_data *d, >>>>>> static struct irq_chip plic_chip = { >>>>>> .name = "SiFive PLIC", >>>>>> - /* >>>>>> - * There is no need to mask/unmask PLIC interrupts. They are "masked" >>>>>> - * by reading claim and "unmasked" when writing it back. >>>>>> - */ >>>>>> .irq_enable = plic_irq_enable, >>>>>> .irq_disable = plic_irq_disable, >>>>>> + .irq_mask = plic_irq_mask, >>>>>> + .irq_unmask = plic_irq_unmask, >>>>>> #ifdef CONFIG_SMP >>>>>> .irq_set_affinity = plic_set_affinity, >>>>>> #endif >>>>> >>>>> Can you give the following patch a go? It brings the irq flow in line >>>>> with what the HW can do. It is of course fully untested (not even >>>>> compile tested...). >>>>> >>>>> Thanks, >>>>> >>>>> M. >>>>> >>>>> From c0ce33a992ec18f5d3bac7f70de62b1ba2b42090 Mon Sep 17 00:00:00 2001 >>>>> From: Marc Zyngier <maz@kernel.org> >>>>> Date: Sun, 15 Sep 2019 15:17:45 +0100 >>>>> Subject: [PATCH] irqchip/sifive-plic: Switch to fasteoi flow >>>>> >>>>> The SiFive PLIC interrupt controller seems to have all the HW >>>>> features to support the fasteoi flow, but the driver seems to be >>>>> stuck in a distant past. Bring it into the 21st century. >>>> >>>> Thanks. We'd gotten these comments during the review process but >>>> nobody had gotten the time to actually fix the issues. >>> >>> No worries. The IRQ subsystem is an acquired taste... ;-) >>> >>>>> >>>>> Signed-off-by: Marc Zyngier <maz@kernel.org> >>>>> --- >>>>> drivers/irqchip/irq-sifive-plic.c | 29 +++++++++++++++-------------- >>>>> 1 file changed, 15 insertions(+), 14 deletions(-) >>>>> >>>>> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c >>>>> index cf755964f2f8..8fea384d392b 100644 >>>>> --- a/drivers/irqchip/irq-sifive-plic.c >>>>> +++ b/drivers/irqchip/irq-sifive-plic.c >>>>> @@ -97,7 +97,7 @@ static inline void plic_irq_toggle(const struct cpumask *mask, >>>>> } >>>>> } >>>>> -static void plic_irq_enable(struct irq_data *d) >>>>> +static void plic_irq_mask(struct irq_data *d) >>> >>> Of course, this is wrong. The perks of trying to do something at the >>> last minute while boarding an airplane. Don't do that. >>> >>> This should of course read "plic_irq_unmask"... >>> >>>>> { >>>>> unsigned int cpu = cpumask_any_and(irq_data_get_affinity_mask(d), >>>>> cpu_online_mask); >>>>> @@ -106,7 +106,7 @@ static void plic_irq_enable(struct irq_data *d) >>>>> plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1); >>>>> } >>>>> -static void plic_irq_disable(struct irq_data *d) >>>>> +static void plic_irq_unmask(struct irq_data *d) >>> >>> ... and this should be "plic_irq_mask". >>> >>> [...] >>> >>>> Reviewed-by: Palmer Dabbelt <palmer@sifive.com> >>>> Tested-by: Palmer Dabbelt <palmer@sifive.com> (QEMU Boot) >>> >>> Huhuh... It may be that QEMU doesn't implement the full-fat PLIC, as >>> the above bug should have kept the IRQ lines masked. >>> >>>> We should test them on the hardware, but I don't have any with me >>>> right now. David's probably in the best spot to do this, as he's got >>>> a setup that does all the weird interrupt sources (ie, PCIe). >>>> >>>> David: do you mind testing this? I've put the patch here: >>>> >>>> ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/palmer/linux.git >>>> -b plic-fasteoi >>> >>> I've pushed out a branch with the fixed patch: >>> >>> git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git irq/plic-fasteoi >>> >> >> That patch works for me on real-ish hardware. I tried on two FPGA >> systems that have different PLIC implementations. Both include >> a PCIe root port (and associated interrupt source). So for >> whatever it's worth: >> >> Tested-by: Darius Rad <darius@bluespec.com> > > Awesome, thanks. Would it be OK to put a "(on two hardware PLIC implementations)" after that, just so we're clear as to who tested what? Fine by me. > > Assuming one of yours wasn't a SiFive PLIC then it'd be great if David could still give this a whack, but I don't think it strictly needs to block merging the patch. I've included the right David this time, with any luck that will be more fruitful :) One of the systems I tested was based on rocket-chip, and the associated PLIC, which I guess is the SiFive PLIC, right? Can't hurt to have more testing, though. > >> >>> Thanks, >>> >>> M. >>>
On Mon, 16 Sep 2019 14:33:23 PDT (-0700), maz@kernel.org wrote: > On Mon, 16 Sep 2019 13:51:58 -0700 (PDT) > Palmer Dabbelt <palmer@sifive.com> wrote: > >> On Mon, 16 Sep 2019 12:04:56 PDT (-0700), Darius Rad wrote: >> > On 9/15/19 2:20 PM, Marc Zyngier wrote: >> >> On Sun, 15 Sep 2019 18:31:33 +0100, >> >> Palmer Dabbelt <palmer@sifive.com> wrote: >> >> >> >> Hi Palmer, >> >> >> >>> >> >>> On Sun, 15 Sep 2019 07:24:20 PDT (-0700), maz@kernel.org wrote: >> >>>> On Thu, 12 Sep 2019 22:40:34 +0100, >> >>>> Darius Rad <darius@bluespec.com> wrote: >> >>>> >> >>>> Hi Darius, >> >>>> >> >>>>> >> >>>>> As per the existing comment, irq_mask and irq_unmask do not need >> >>>>> to do anything for the PLIC. However, the functions must exist >> >>>>> (the pointers cannot be NULL) as they are not optional, based on >> >>>>> the documentation (Documentation/core-api/genericirq.rst) as well >> >>>>> as existing usage (e.g., include/linux/irqchip/chained_irq.h). >> >>>>> >> >>>>> Signed-off-by: Darius Rad <darius@bluespec.com> >> >>>>> --- >> >>>>> drivers/irqchip/irq-sifive-plic.c | 13 +++++++++---- >> >>>>> 1 file changed, 9 insertions(+), 4 deletions(-) >> >>>>> >> >>>>> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c >> >>>>> index cf755964f2f8..52d5169f924f 100644 >> >>>>> --- a/drivers/irqchip/irq-sifive-plic.c >> >>>>> +++ b/drivers/irqchip/irq-sifive-plic.c >> >>>>> @@ -111,6 +111,13 @@ static void plic_irq_disable(struct irq_data *d) >> >>>>> plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); >> >>>>> } >> >>>>> +/* >> >>>>> + * There is no need to mask/unmask PLIC interrupts. They are "masked" >> >>>>> + * by reading claim and "unmasked" when writing it back. >> >>>>> + */ >> >>>>> +static void plic_irq_mask(struct irq_data *d) { } >> >>>>> +static void plic_irq_unmask(struct irq_data *d) { } >> >>>> >> >>>> This outlines a bigger issue. If your irqchip doesn't require >> >>>> mask/unmask, you're probably not using the right interrupt >> >>>> flow. Looking at the code, I see you're using handle_simple_irq, which >> >>>> is almost universally wrong. >> >>>> >> >>>> As per the description above, these interrupts should be using the >> >>>> fasteoi flow, which is designed for this exact behaviour (the >> >>>> interrupt controller knows which interrupt is in flight and doesn't >> >>>> require SW to do anything bar signalling the EOI). >> >>>> >> >>>> Another thing is that mask/unmask tends to be a requirement, while >> >>>> enable/disable tends to be optional. There is no hard line here, but >> >>>> the expectations are that: >> >>>> >> >>>> (a) A disabled line can drop interrupts >> >>>> (b) A masked line cannot drop interrupts >> >>>> >> >>>> Depending what the PLIC architecture mandates, you'll need to >> >>>> implement one and/or the other. Having just (a) is indicative of a HW >> >>>> bug, and I'm not assuming that this is the case. (b) only is pretty >> >>>> common, and (a)+(b) has a few adepts. My bet is that it requires (b) >> >>>> only. >> >>>> >> >>>>> + >> >>>>> #ifdef CONFIG_SMP >> >>>>> static int plic_set_affinity(struct irq_data *d, >> >>>>> const struct cpumask *mask_val, bool force) >> >>>>> @@ -138,12 +145,10 @@ static int plic_set_affinity(struct irq_data *d, >> >>>>> static struct irq_chip plic_chip = { >> >>>>> .name = "SiFive PLIC", >> >>>>> - /* >> >>>>> - * There is no need to mask/unmask PLIC interrupts. They are "masked" >> >>>>> - * by reading claim and "unmasked" when writing it back. >> >>>>> - */ >> >>>>> .irq_enable = plic_irq_enable, >> >>>>> .irq_disable = plic_irq_disable, >> >>>>> + .irq_mask = plic_irq_mask, >> >>>>> + .irq_unmask = plic_irq_unmask, >> >>>>> #ifdef CONFIG_SMP >> >>>>> .irq_set_affinity = plic_set_affinity, >> >>>>> #endif >> >>>> >> >>>> Can you give the following patch a go? It brings the irq flow in line >> >>>> with what the HW can do. It is of course fully untested (not even >> >>>> compile tested...). >> >>>> >> >>>> Thanks, >> >>>> >> >>>> M. >> >>>> >> >>>> From c0ce33a992ec18f5d3bac7f70de62b1ba2b42090 Mon Sep 17 00:00:00 2001 >> >>>> From: Marc Zyngier <maz@kernel.org> >> >>>> Date: Sun, 15 Sep 2019 15:17:45 +0100 >> >>>> Subject: [PATCH] irqchip/sifive-plic: Switch to fasteoi flow >> >>>> >> >>>> The SiFive PLIC interrupt controller seems to have all the HW >> >>>> features to support the fasteoi flow, but the driver seems to be >> >>>> stuck in a distant past. Bring it into the 21st century. >> >>> >> >>> Thanks. We'd gotten these comments during the review process but >> >>> nobody had gotten the time to actually fix the issues. >> >> >> >> No worries. The IRQ subsystem is an acquired taste... ;-) >> >> >> >>>> >> >>>> Signed-off-by: Marc Zyngier <maz@kernel.org> >> >>>> --- >> >>>> drivers/irqchip/irq-sifive-plic.c | 29 +++++++++++++++-------------- >> >>>> 1 file changed, 15 insertions(+), 14 deletions(-) >> >>>> >> >>>> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c >> >>>> index cf755964f2f8..8fea384d392b 100644 >> >>>> --- a/drivers/irqchip/irq-sifive-plic.c >> >>>> +++ b/drivers/irqchip/irq-sifive-plic.c >> >>>> @@ -97,7 +97,7 @@ static inline void plic_irq_toggle(const struct cpumask *mask, >> >>>> } >> >>>> } >> >>>> -static void plic_irq_enable(struct irq_data *d) >> >>>> +static void plic_irq_mask(struct irq_data *d) >> >> >> >> Of course, this is wrong. The perks of trying to do something at the >> >> last minute while boarding an airplane. Don't do that. >> >> >> >> This should of course read "plic_irq_unmask"... >> >> >> >>>> { >> >>>> unsigned int cpu = cpumask_any_and(irq_data_get_affinity_mask(d), >> >>>> cpu_online_mask); >> >>>> @@ -106,7 +106,7 @@ static void plic_irq_enable(struct irq_data *d) >> >>>> plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1); >> >>>> } >> >>>> -static void plic_irq_disable(struct irq_data *d) >> >>>> +static void plic_irq_unmask(struct irq_data *d) >> >> >> >> ... and this should be "plic_irq_mask". >> >> >> >> [...] >> >> >> >>> Reviewed-by: Palmer Dabbelt <palmer@sifive.com> >> >>> Tested-by: Palmer Dabbelt <palmer@sifive.com> (QEMU Boot) >> >> >> >> Huhuh... It may be that QEMU doesn't implement the full-fat PLIC, as >> >> the above bug should have kept the IRQ lines masked. >> >> >> >>> We should test them on the hardware, but I don't have any with me >> >>> right now. David's probably in the best spot to do this, as he's got >> >>> a setup that does all the weird interrupt sources (ie, PCIe). >> >>> >> >>> David: do you mind testing this? I've put the patch here: >> >>> >> >>> ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/palmer/linux.git >> >>> -b plic-fasteoi >> >> >> >> I've pushed out a branch with the fixed patch: >> >> >> >> git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git irq/plic-fasteoi >> >> >> > >> > That patch works for me on real-ish hardware. I tried on two FPGA >> > systems that have different PLIC implementations. Both include >> > a PCIe root port (and associated interrupt source). So for >> > whatever it's worth: >> > >> > Tested-by: Darius Rad <darius@bluespec.com> >> >> Awesome, thanks. Would it be OK to put a "(on two hardware PLIC >> implementations)" after that, just so we're clear as to who tested >> what? > > Sure, no problem. > >> Assuming one of yours wasn't a SiFive PLIC then it'd be great if >> David could still give this a whack, but I don't think it strictly >> needs to block merging the patch. I've included the right David this >> time, with any luck that will be more fruitful :) > > Well, we still have time before -rc1. Once David gets a chance to test > it, I'll apply it. Additional question: do you want this backported to > -stable? If so, how far? Generally I've just been CCing stable on bug fixes and letting the automation handle it. 4.19 was the first version with a PLIC driver, and that was pretty broken so this should be deep down in the noise for anyone who's trying to use that -- and I doubt anyone is trying to do so. > > Thanks, > > M.
On Mon, 16 Sep 2019 14:41:07 PDT (-0700), Darius Rad wrote: > On 9/16/19 4:51 PM, Palmer Dabbelt wrote: >> On Mon, 16 Sep 2019 12:04:56 PDT (-0700), Darius Rad wrote: >>> On 9/15/19 2:20 PM, Marc Zyngier wrote: >>>> On Sun, 15 Sep 2019 18:31:33 +0100, >>>> Palmer Dabbelt <palmer@sifive.com> wrote: >>>> >>>> Hi Palmer, >>>> >>>>> >>>>> On Sun, 15 Sep 2019 07:24:20 PDT (-0700), maz@kernel.org wrote: >>>>>> On Thu, 12 Sep 2019 22:40:34 +0100, >>>>>> Darius Rad <darius@bluespec.com> wrote: >>>>>> >>>>>> Hi Darius, >>>>>> >>>>>>> >>>>>>> As per the existing comment, irq_mask and irq_unmask do not need >>>>>>> to do anything for the PLIC. However, the functions must exist >>>>>>> (the pointers cannot be NULL) as they are not optional, based on >>>>>>> the documentation (Documentation/core-api/genericirq.rst) as well >>>>>>> as existing usage (e.g., include/linux/irqchip/chained_irq.h). >>>>>>> >>>>>>> Signed-off-by: Darius Rad <darius@bluespec.com> >>>>>>> --- >>>>>>> drivers/irqchip/irq-sifive-plic.c | 13 +++++++++---- >>>>>>> 1 file changed, 9 insertions(+), 4 deletions(-) >>>>>>> >>>>>>> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c >>>>>>> index cf755964f2f8..52d5169f924f 100644 >>>>>>> --- a/drivers/irqchip/irq-sifive-plic.c >>>>>>> +++ b/drivers/irqchip/irq-sifive-plic.c >>>>>>> @@ -111,6 +111,13 @@ static void plic_irq_disable(struct irq_data *d) >>>>>>> plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); >>>>>>> } >>>>>>> +/* >>>>>>> + * There is no need to mask/unmask PLIC interrupts. They are "masked" >>>>>>> + * by reading claim and "unmasked" when writing it back. >>>>>>> + */ >>>>>>> +static void plic_irq_mask(struct irq_data *d) { } >>>>>>> +static void plic_irq_unmask(struct irq_data *d) { } >>>>>> >>>>>> This outlines a bigger issue. If your irqchip doesn't require >>>>>> mask/unmask, you're probably not using the right interrupt >>>>>> flow. Looking at the code, I see you're using handle_simple_irq, which >>>>>> is almost universally wrong. >>>>>> >>>>>> As per the description above, these interrupts should be using the >>>>>> fasteoi flow, which is designed for this exact behaviour (the >>>>>> interrupt controller knows which interrupt is in flight and doesn't >>>>>> require SW to do anything bar signalling the EOI). >>>>>> >>>>>> Another thing is that mask/unmask tends to be a requirement, while >>>>>> enable/disable tends to be optional. There is no hard line here, but >>>>>> the expectations are that: >>>>>> >>>>>> (a) A disabled line can drop interrupts >>>>>> (b) A masked line cannot drop interrupts >>>>>> >>>>>> Depending what the PLIC architecture mandates, you'll need to >>>>>> implement one and/or the other. Having just (a) is indicative of a HW >>>>>> bug, and I'm not assuming that this is the case. (b) only is pretty >>>>>> common, and (a)+(b) has a few adepts. My bet is that it requires (b) >>>>>> only. >>>>>> >>>>>>> + >>>>>>> #ifdef CONFIG_SMP >>>>>>> static int plic_set_affinity(struct irq_data *d, >>>>>>> const struct cpumask *mask_val, bool force) >>>>>>> @@ -138,12 +145,10 @@ static int plic_set_affinity(struct irq_data *d, >>>>>>> static struct irq_chip plic_chip = { >>>>>>> .name = "SiFive PLIC", >>>>>>> - /* >>>>>>> - * There is no need to mask/unmask PLIC interrupts. They are "masked" >>>>>>> - * by reading claim and "unmasked" when writing it back. >>>>>>> - */ >>>>>>> .irq_enable = plic_irq_enable, >>>>>>> .irq_disable = plic_irq_disable, >>>>>>> + .irq_mask = plic_irq_mask, >>>>>>> + .irq_unmask = plic_irq_unmask, >>>>>>> #ifdef CONFIG_SMP >>>>>>> .irq_set_affinity = plic_set_affinity, >>>>>>> #endif >>>>>> >>>>>> Can you give the following patch a go? It brings the irq flow in line >>>>>> with what the HW can do. It is of course fully untested (not even >>>>>> compile tested...). >>>>>> >>>>>> Thanks, >>>>>> >>>>>> M. >>>>>> >>>>>> From c0ce33a992ec18f5d3bac7f70de62b1ba2b42090 Mon Sep 17 00:00:00 2001 >>>>>> From: Marc Zyngier <maz@kernel.org> >>>>>> Date: Sun, 15 Sep 2019 15:17:45 +0100 >>>>>> Subject: [PATCH] irqchip/sifive-plic: Switch to fasteoi flow >>>>>> >>>>>> The SiFive PLIC interrupt controller seems to have all the HW >>>>>> features to support the fasteoi flow, but the driver seems to be >>>>>> stuck in a distant past. Bring it into the 21st century. >>>>> >>>>> Thanks. We'd gotten these comments during the review process but >>>>> nobody had gotten the time to actually fix the issues. >>>> >>>> No worries. The IRQ subsystem is an acquired taste... ;-) >>>> >>>>>> >>>>>> Signed-off-by: Marc Zyngier <maz@kernel.org> >>>>>> --- >>>>>> drivers/irqchip/irq-sifive-plic.c | 29 +++++++++++++++-------------- >>>>>> 1 file changed, 15 insertions(+), 14 deletions(-) >>>>>> >>>>>> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c >>>>>> index cf755964f2f8..8fea384d392b 100644 >>>>>> --- a/drivers/irqchip/irq-sifive-plic.c >>>>>> +++ b/drivers/irqchip/irq-sifive-plic.c >>>>>> @@ -97,7 +97,7 @@ static inline void plic_irq_toggle(const struct cpumask *mask, >>>>>> } >>>>>> } >>>>>> -static void plic_irq_enable(struct irq_data *d) >>>>>> +static void plic_irq_mask(struct irq_data *d) >>>> >>>> Of course, this is wrong. The perks of trying to do something at the >>>> last minute while boarding an airplane. Don't do that. >>>> >>>> This should of course read "plic_irq_unmask"... >>>> >>>>>> { >>>>>> unsigned int cpu = cpumask_any_and(irq_data_get_affinity_mask(d), >>>>>> cpu_online_mask); >>>>>> @@ -106,7 +106,7 @@ static void plic_irq_enable(struct irq_data *d) >>>>>> plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1); >>>>>> } >>>>>> -static void plic_irq_disable(struct irq_data *d) >>>>>> +static void plic_irq_unmask(struct irq_data *d) >>>> >>>> ... and this should be "plic_irq_mask". >>>> >>>> [...] >>>> >>>>> Reviewed-by: Palmer Dabbelt <palmer@sifive.com> >>>>> Tested-by: Palmer Dabbelt <palmer@sifive.com> (QEMU Boot) >>>> >>>> Huhuh... It may be that QEMU doesn't implement the full-fat PLIC, as >>>> the above bug should have kept the IRQ lines masked. >>>> >>>>> We should test them on the hardware, but I don't have any with me >>>>> right now. David's probably in the best spot to do this, as he's got >>>>> a setup that does all the weird interrupt sources (ie, PCIe). >>>>> >>>>> David: do you mind testing this? I've put the patch here: >>>>> >>>>> ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/palmer/linux.git >>>>> -b plic-fasteoi >>>> >>>> I've pushed out a branch with the fixed patch: >>>> >>>> git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git irq/plic-fasteoi >>>> >>> >>> That patch works for me on real-ish hardware. I tried on two FPGA >>> systems that have different PLIC implementations. Both include >>> a PCIe root port (and associated interrupt source). So for >>> whatever it's worth: >>> >>> Tested-by: Darius Rad <darius@bluespec.com> >> >> Awesome, thanks. Would it be OK to put a "(on two hardware PLIC implementations)" after that, just so we're clear as to who tested what? > > Fine by me. > >> >> Assuming one of yours wasn't a SiFive PLIC then it'd be great if David could still give this a whack, but I don't think it strictly needs to block merging the patch. I've included the right David this time, with any luck that will be more fruitful :) > > One of the systems I tested was based on rocket-chip, and the > associated PLIC, which I guess is the SiFive PLIC, right? Can't hurt > to have more testing, though. Ya, that's ours. > >> >>> >>>> Thanks, >>>> >>>> M. >>>>
With the fixes it seems to still work fine on the Kendryte KD210. Although currently only the serial interrupt is tested and this might not be a very exhaustive test case..
Just tested this on the SiFive HiFive Unleashed. Seems to work OK;
however I did not stress-test it.
Tested-by: Paul Walmsley <paul.walmsley@sifive.com> # HiFive Unleashed
- Paul
# !cat
cat /proc/interrupts
CPU0 CPU1 CPU2 CPU3
1: 0 0 0 0 SiFive PLIC 5 10011000.serial
3: 0 0 0 0 SiFive PLIC 51 10040000.spi
4: 6266 0 0 0 SiFive PLIC 4 10010000.serial
5: 102 0 0 0 SiFive PLIC 6 10050000.spi
6: 37 0 0 0 SiFive PLIC 53 eth0
IPI0: 1134 21128 9024 220261 Rescheduling interrupts
IPI1: 10 143 18 7 Function call interrupts
IPI2: 0 0 0 0 CPU stop interrupts
#
On Tue, Sep 17, 2019 at 3:26 PM Paul Walmsley <paul.walmsley@sifive.com> wrote: > > > Just tested this on the SiFive HiFive Unleashed. Seems to work OK; > however I did not stress-test it. > > Tested-by: Paul Walmsley <paul.walmsley@sifive.com> # HiFive Unleashed > > > - Paul > > > # !cat > cat /proc/interrupts > CPU0 CPU1 CPU2 CPU3 > 1: 0 0 0 0 SiFive PLIC 5 10011000.serial > 3: 0 0 0 0 SiFive PLIC 51 10040000.spi > 4: 6266 0 0 0 SiFive PLIC 4 10010000.serial > 5: 102 0 0 0 SiFive PLIC 6 10050000.spi > 6: 37 0 0 0 SiFive PLIC 53 eth0 > IPI0: 1134 21128 9024 220261 Rescheduling interrupts > IPI1: 10 143 18 7 Function call interrupts > IPI2: 0 0 0 0 CPU stop interrupts > # I have applied the patch on top of 5.2.9 kernel and tried to stress it with stress-ng interrupt stressors for 2:30+ hours. # cat /proc/interrupts CPU0 CPU1 CPU2 CPU3 1: 0 0 0 0 SiFive PLIC 5 10011000.serial 3: 0 0 0 0 SiFive PLIC 51 10040000.spi 4: 34240 0 0 0 SiFive PLIC 4 10010000.serial 5: 102 0 0 0 SiFive PLIC 6 10050000.spi 6: 0 0 0 0 SiFive PLIC 53 eth0 7: 0 0 0 0 SiFive PLIC 32 microsemi-pcie IPI0: 32013933 28068736 29345256 23346339 Rescheduling interrupts IPI1: 78514 78586 63144 100317 Function call interrupts IPI2: 0 0 0 0 CPU stop interrupts
diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c index cf755964f2f8..52d5169f924f 100644 --- a/drivers/irqchip/irq-sifive-plic.c +++ b/drivers/irqchip/irq-sifive-plic.c @@ -111,6 +111,13 @@ static void plic_irq_disable(struct irq_data *d) plic_irq_toggle(cpu_possible_mask, d->hwirq, 0); } +/* + * There is no need to mask/unmask PLIC interrupts. They are "masked" + * by reading claim and "unmasked" when writing it back. + */ +static void plic_irq_mask(struct irq_data *d) { } +static void plic_irq_unmask(struct irq_data *d) { } + #ifdef CONFIG_SMP static int plic_set_affinity(struct irq_data *d, const struct cpumask *mask_val, bool force) @@ -138,12 +145,10 @@ static int plic_set_affinity(struct irq_data *d, static struct irq_chip plic_chip = { .name = "SiFive PLIC", - /* - * There is no need to mask/unmask PLIC interrupts. They are "masked" - * by reading claim and "unmasked" when writing it back. - */ .irq_enable = plic_irq_enable, .irq_disable = plic_irq_disable, + .irq_mask = plic_irq_mask, + .irq_unmask = plic_irq_unmask, #ifdef CONFIG_SMP .irq_set_affinity = plic_set_affinity, #endif
As per the existing comment, irq_mask and irq_unmask do not need to do anything for the PLIC. However, the functions must exist (the pointers cannot be NULL) as they are not optional, based on the documentation (Documentation/core-api/genericirq.rst) as well as existing usage (e.g., include/linux/irqchip/chained_irq.h). Signed-off-by: Darius Rad <darius@bluespec.com> --- drivers/irqchip/irq-sifive-plic.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-)