| Message ID | 1485334353-26815-1-git-send-email-bharatku@xilinx.com (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
The subject line is not very descriptive. How about "Enforce level triggering for legacy interrupts"? On 25/01/17 08:52, Bharat Kumar Gogada wrote: > - Few wifi end points which only support legacy interrupts, > performs hardware reset functionalities after disabling interrupts > by invoking disable_irq and then re-enable using enable_irq, they > enable hardware interrupts first and then virtual irq line later. > - The legacy irq line goes low only after DEASSERT_INTx is > received.As the legacy irq line is high immediately after hardware > interrupts are enabled but virq of EP is still in disabled state > and EP handler is never executed resulting no DEASSERT_INTx.If dummy > irq chip is used, interrutps are not masked and system is interrupts > hanging with CPU stall. > - Adding irq chip functions instead of dummy irq chip for legacy > interrupts. > - Legacy interrupts are level sensitive, so using handle_level_irq > is more appropriate as it is masks interrupts until End point handles > interrupts and unmasks interrutps after End point handler is executed. interrupts > > Signed-off-by: Bharat Kumar Gogada <bharatku@xilinx.com> > --- > drivers/pci/host/pcie-xilinx-nwl.c | 36 +++++++++++++++++++++++++++++++++++- > 1 file changed, 35 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/host/pcie-xilinx-nwl.c b/drivers/pci/host/pcie-xilinx-nwl.c > index 43eaa4a..6ac3e1d 100644 > --- a/drivers/pci/host/pcie-xilinx-nwl.c > +++ b/drivers/pci/host/pcie-xilinx-nwl.c > @@ -395,10 +395,44 @@ static void nwl_pcie_msi_handler_low(struct irq_desc *desc) > chained_irq_exit(chip, desc); > } > > +static void nwl_mask_leg_irq(struct irq_data *data) > +{ > + struct irq_desc *desc = irq_to_desc(data->irq); > + struct nwl_pcie *pcie; > + u32 mask; > + u32 val; > + > + pcie = irq_desc_get_chip_data(desc); > + mask = 1 << (data->hwirq - 1); > + val = nwl_bridge_readl(pcie, MSGF_LEG_MASK); > + nwl_bridge_writel(pcie, (val & (~mask)), MSGF_LEG_MASK); Oh please! Think of the following: cpu0 cpu1 read read write write How can you make this reliable if you don't have any form of mutual exclusion that spans both mask and unmask, and ensures the atomicity of the RMW sequence? Thanks, M.
> The subject line is not very descriptive. How about "Enforce level > triggering for legacy interrupts"? > > On 25/01/17 08:52, Bharat Kumar Gogada wrote: > > - Few wifi end points which only support legacy interrupts, > > performs hardware reset functionalities after disabling interrupts > > by invoking disable_irq and then re-enable using enable_irq, they > > enable hardware interrupts first and then virtual irq line later. > > - The legacy irq line goes low only after DEASSERT_INTx is > > received.As the legacy irq line is high immediately after hardware > > interrupts are enabled but virq of EP is still in disabled state > > and EP handler is never executed resulting no DEASSERT_INTx.If dummy > > irq chip is used, interrutps are not masked and system is > > interrupts > > > hanging with CPU stall. > > - Adding irq chip functions instead of dummy irq chip for legacy > > interrupts. > > - Legacy interrupts are level sensitive, so using handle_level_irq > > is more appropriate as it is masks interrupts until End point handles > > interrupts and unmasks interrutps after End point handler is executed. > > interrupts > > > > > Signed-off-by: Bharat Kumar Gogada <bharatku@xilinx.com> > > --- > > drivers/pci/host/pcie-xilinx-nwl.c | 36 > +++++++++++++++++++++++++++++++++++- > > 1 file changed, 35 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/pci/host/pcie-xilinx-nwl.c b/drivers/pci/host/pcie-xilinx- > nwl.c > > index 43eaa4a..6ac3e1d 100644 > > --- a/drivers/pci/host/pcie-xilinx-nwl.c > > +++ b/drivers/pci/host/pcie-xilinx-nwl.c > > @@ -395,10 +395,44 @@ static void nwl_pcie_msi_handler_low(struct > irq_desc *desc) > > chained_irq_exit(chip, desc); > > } > > > > +static void nwl_mask_leg_irq(struct irq_data *data) > > +{ > > + struct irq_desc *desc = irq_to_desc(data->irq); > > + struct nwl_pcie *pcie; > > + u32 mask; > > + u32 val; > > + > > + pcie = irq_desc_get_chip_data(desc); > > + mask = 1 << (data->hwirq - 1); > > + val = nwl_bridge_readl(pcie, MSGF_LEG_MASK); > > + nwl_bridge_writel(pcie, (val & (~mask)), MSGF_LEG_MASK); > > Oh please! Think of the following: > > cpu0 cpu1 > read > read > write > write > > How can you make this reliable if you don't have any form of mutual > exclusion that spans both mask and unmask, and ensures the atomicity of > the RMW sequence? > Agreed, will send with locks. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/pci/host/pcie-xilinx-nwl.c b/drivers/pci/host/pcie-xilinx-nwl.c index 43eaa4a..6ac3e1d 100644 --- a/drivers/pci/host/pcie-xilinx-nwl.c +++ b/drivers/pci/host/pcie-xilinx-nwl.c @@ -395,10 +395,44 @@ static void nwl_pcie_msi_handler_low(struct irq_desc *desc) chained_irq_exit(chip, desc); } +static void nwl_mask_leg_irq(struct irq_data *data) +{ + struct irq_desc *desc = irq_to_desc(data->irq); + struct nwl_pcie *pcie; + u32 mask; + u32 val; + + pcie = irq_desc_get_chip_data(desc); + mask = 1 << (data->hwirq - 1); + val = nwl_bridge_readl(pcie, MSGF_LEG_MASK); + nwl_bridge_writel(pcie, (val & (~mask)), MSGF_LEG_MASK); +} + +static void nwl_unmask_leg_irq(struct irq_data *data) +{ + struct irq_desc *desc = irq_to_desc(data->irq); + struct nwl_pcie *pcie; + u32 mask; + u32 val; + + pcie = irq_desc_get_chip_data(desc); + mask = 1 << (data->hwirq - 1); + val = nwl_bridge_readl(pcie, MSGF_LEG_MASK); + nwl_bridge_writel(pcie, (val | mask), MSGF_LEG_MASK); +} + +static struct irq_chip nwl_leg_irq_chip = { + .name = "nwl_pcie:legacy", + .irq_enable = nwl_unmask_leg_irq, + .irq_disable = nwl_mask_leg_irq, + .irq_mask = nwl_mask_leg_irq, + .irq_unmask = nwl_unmask_leg_irq, +}; + static int nwl_legacy_map(struct irq_domain *domain, unsigned int irq, irq_hw_number_t hwirq) { - irq_set_chip_and_handler(irq, &dummy_irq_chip, handle_simple_irq); + irq_set_chip_and_handler(irq, &nwl_leg_irq_chip, handle_level_irq); irq_set_chip_data(irq, domain->host_data); return 0;
- Few wifi end points which only support legacy interrupts, performs hardware reset functionalities after disabling interrupts by invoking disable_irq and then re-enable using enable_irq, they enable hardware interrupts first and then virtual irq line later. - The legacy irq line goes low only after DEASSERT_INTx is received.As the legacy irq line is high immediately after hardware interrupts are enabled but virq of EP is still in disabled state and EP handler is never executed resulting no DEASSERT_INTx.If dummy irq chip is used, interrutps are not masked and system is hanging with CPU stall. - Adding irq chip functions instead of dummy irq chip for legacy interrupts. - Legacy interrupts are level sensitive, so using handle_level_irq is more appropriate as it is masks interrupts until End point handles interrupts and unmasks interrutps after End point handler is executed. Signed-off-by: Bharat Kumar Gogada <bharatku@xilinx.com> --- drivers/pci/host/pcie-xilinx-nwl.c | 36 +++++++++++++++++++++++++++++++++++- 1 file changed, 35 insertions(+), 1 deletion(-)