| Message ID | 1410872360-27029-4-git-send-email-k.kozlowski@samsung.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On 16 September 2014 14:59, Krzysztof Kozlowski <k.kozlowski@samsung.com> wrote: > The AMBA bus driver defines runtime Power Management functions which > disable and unprepare AMBA bus clock. This is problematic for runtime PM > because unpreparing a clock might sleep so it is not interrupt safe. > > However some drivers may want to implement runtime PM functions in > interrupt-safe way (see pm_runtime_irq_safe()). In such case the AMBA > bus driver should only disable/enable the clock in runtime suspend and > resume callbacks. > > Detect the device driver behavior after calling its probe function and > store it. During runtime suspend/resume deal with clocks according to > stored value. > > Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com> > --- > drivers/amba/bus.c | 29 +++++++++++++++++++++++++---- > include/linux/amba/bus.h | 1 + > 2 files changed, 26 insertions(+), 4 deletions(-) > > diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c > index 3cf61a127ee5..e8fd5706954f 100644 > --- a/drivers/amba/bus.c > +++ b/drivers/amba/bus.c > @@ -94,8 +94,18 @@ static int amba_pm_runtime_suspend(struct device *dev) > struct amba_device *pcdev = to_amba_device(dev); > int ret = pm_generic_runtime_suspend(dev); > > - if (ret == 0 && dev->driver) > - clk_disable_unprepare(pcdev->pclk); > + if (ret == 0 && dev->driver) { > + /* > + * Drivers should not change pm_runtime_irq_safe() > + * after probe. > + */ > + WARN_ON(pcdev->irq_safe != pm_runtime_is_irq_safe(dev)); Do we really need a WARN_ON here. Driver shouldn't update their irq_safe value dynamically, right!? > + > + if (pcdev->irq_safe) > + clk_disable(pcdev->pclk); Since the irq_safe flag, could be considered as a special case, an option for these cases - could be to leave the clock to be entirely handled from the driver's runtime PM callback instead. I wonder if that could simplify both for the driver and for the amba bus? Russell, what do you think? Is it a bad idea? > + else > + clk_disable_unprepare(pcdev->pclk); > + } > > return ret; > } > @@ -106,7 +116,16 @@ static int amba_pm_runtime_resume(struct device *dev) > int ret; > > if (dev->driver) { > - ret = clk_prepare_enable(pcdev->pclk); > + /* > + * Drivers should not change pm_runtime_irq_safe() > + * after probe. > + */ > + WARN_ON(pcdev->irq_safe != pm_runtime_is_irq_safe(dev)); > + > + if (pcdev->irq_safe) > + ret = clk_enable(pcdev->pclk); > + else > + ret = clk_prepare_enable(pcdev->pclk); > /* Failure is probably fatal to the system, but... */ > if (ret) > return ret; > @@ -191,8 +210,10 @@ static int amba_probe(struct device *dev) > pm_runtime_enable(dev); > > ret = pcdrv->probe(pcdev, id); > - if (ret == 0) > + if (ret == 0) { > + pcdev->irq_safe = pm_runtime_is_irq_safe(dev); I suggest to remove the local copy of this flag and to use pm_runtime_is_irq_safe(dev) directly instead. > break; > + } > > pm_runtime_disable(dev); > pm_runtime_set_suspended(dev); > diff --git a/include/linux/amba/bus.h b/include/linux/amba/bus.h > index ad52027a9cbf..ce101e4497d6 100644 > --- a/include/linux/amba/bus.h > +++ b/include/linux/amba/bus.h > @@ -32,6 +32,7 @@ struct amba_device { > struct clk *pclk; > unsigned int periphid; > unsigned int irq[AMBA_NR_IRQS]; > + unsigned int irq_safe:1; > }; > > struct amba_driver { > -- > 1.9.1 > Kind regards Uffe -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Sep 16, 2014 at 08:25:25PM +0200, Ulf Hansson wrote: > On 16 September 2014 14:59, Krzysztof Kozlowski <k.kozlowski@samsung.com> wrote: > > The AMBA bus driver defines runtime Power Management functions which > > disable and unprepare AMBA bus clock. This is problematic for runtime PM > > because unpreparing a clock might sleep so it is not interrupt safe. > > > > However some drivers may want to implement runtime PM functions in > > interrupt-safe way (see pm_runtime_irq_safe()). In such case the AMBA > > bus driver should only disable/enable the clock in runtime suspend and > > resume callbacks. > > > > Detect the device driver behavior after calling its probe function and > > store it. During runtime suspend/resume deal with clocks according to > > stored value. > > > > Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com> > > --- > > drivers/amba/bus.c | 29 +++++++++++++++++++++++++---- > > include/linux/amba/bus.h | 1 + > > 2 files changed, 26 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c > > index 3cf61a127ee5..e8fd5706954f 100644 > > --- a/drivers/amba/bus.c > > +++ b/drivers/amba/bus.c > > @@ -94,8 +94,18 @@ static int amba_pm_runtime_suspend(struct device *dev) > > struct amba_device *pcdev = to_amba_device(dev); > > int ret = pm_generic_runtime_suspend(dev); > > > > - if (ret == 0 && dev->driver) > > - clk_disable_unprepare(pcdev->pclk); > > + if (ret == 0 && dev->driver) { > > + /* > > + * Drivers should not change pm_runtime_irq_safe() > > + * after probe. > > + */ > > + WARN_ON(pcdev->irq_safe != pm_runtime_is_irq_safe(dev)); > > Do we really need a WARN_ON here. Driver shouldn't update their > irq_safe value dynamically, right!? The driver shouldn't update it dynamically, and this makes sure *that* is enforced since we end up depending on that property. Hence the check is sensible (and I even suggested it.) > > + > > + if (pcdev->irq_safe) > > + clk_disable(pcdev->pclk); > > Since the irq_safe flag, could be considered as a special case, an > option for these cases - could be to leave the clock to be entirely > handled from the driver's runtime PM callback instead. Too many sub-clauses to make much sense of that statement. I don't want drivers messing around with this stuff. This is the /bus/ clock, not a device specific clock.
On 16 September 2014 21:52, Russell King - ARM Linux <linux@arm.linux.org.uk> wrote: > On Tue, Sep 16, 2014 at 08:25:25PM +0200, Ulf Hansson wrote: >> On 16 September 2014 14:59, Krzysztof Kozlowski <k.kozlowski@samsung.com> wrote: >> > The AMBA bus driver defines runtime Power Management functions which >> > disable and unprepare AMBA bus clock. This is problematic for runtime PM >> > because unpreparing a clock might sleep so it is not interrupt safe. >> > >> > However some drivers may want to implement runtime PM functions in >> > interrupt-safe way (see pm_runtime_irq_safe()). In such case the AMBA >> > bus driver should only disable/enable the clock in runtime suspend and >> > resume callbacks. >> > >> > Detect the device driver behavior after calling its probe function and >> > store it. During runtime suspend/resume deal with clocks according to >> > stored value. >> > >> > Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com> >> > --- >> > drivers/amba/bus.c | 29 +++++++++++++++++++++++++---- >> > include/linux/amba/bus.h | 1 + >> > 2 files changed, 26 insertions(+), 4 deletions(-) >> > >> > diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c >> > index 3cf61a127ee5..e8fd5706954f 100644 >> > --- a/drivers/amba/bus.c >> > +++ b/drivers/amba/bus.c >> > @@ -94,8 +94,18 @@ static int amba_pm_runtime_suspend(struct device *dev) >> > struct amba_device *pcdev = to_amba_device(dev); >> > int ret = pm_generic_runtime_suspend(dev); >> > >> > - if (ret == 0 && dev->driver) >> > - clk_disable_unprepare(pcdev->pclk); >> > + if (ret == 0 && dev->driver) { >> > + /* >> > + * Drivers should not change pm_runtime_irq_safe() >> > + * after probe. >> > + */ >> > + WARN_ON(pcdev->irq_safe != pm_runtime_is_irq_safe(dev)); >> >> Do we really need a WARN_ON here. Driver shouldn't update their >> irq_safe value dynamically, right!? > > The driver shouldn't update it dynamically, and this makes sure *that* > is enforced since we end up depending on that property. Hence the > check is sensible (and I even suggested it.) The WARN_ON could be nice to have, but I think this is a task for PM core to handle. Copying flags shouldn't be needed for each an every instance of a driver/bus that manage irq_safe devices. That's my main point. > >> > + >> > + if (pcdev->irq_safe) >> > + clk_disable(pcdev->pclk); >> >> Since the irq_safe flag, could be considered as a special case, an >> option for these cases - could be to leave the clock to be entirely >> handled from the driver's runtime PM callback instead. > > Too many sub-clauses to make much sense of that statement. Sorry, agree. :-) > > I don't want drivers messing around with this stuff. This is the /bus/ > clock, not a device specific clock. For irq_safe devices, driver's will need to handle the clk_prepare|unprepare during system PM anyway. That's the reason to why I suggested this. On the other hand I agree with you, it's a bus clock... Kind regards Uffe -- To unsubscribe from this list: send the line "unsubscribe dmaengine" 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/amba/bus.c b/drivers/amba/bus.c index 3cf61a127ee5..e8fd5706954f 100644 --- a/drivers/amba/bus.c +++ b/drivers/amba/bus.c @@ -94,8 +94,18 @@ static int amba_pm_runtime_suspend(struct device *dev) struct amba_device *pcdev = to_amba_device(dev); int ret = pm_generic_runtime_suspend(dev); - if (ret == 0 && dev->driver) - clk_disable_unprepare(pcdev->pclk); + if (ret == 0 && dev->driver) { + /* + * Drivers should not change pm_runtime_irq_safe() + * after probe. + */ + WARN_ON(pcdev->irq_safe != pm_runtime_is_irq_safe(dev)); + + if (pcdev->irq_safe) + clk_disable(pcdev->pclk); + else + clk_disable_unprepare(pcdev->pclk); + } return ret; } @@ -106,7 +116,16 @@ static int amba_pm_runtime_resume(struct device *dev) int ret; if (dev->driver) { - ret = clk_prepare_enable(pcdev->pclk); + /* + * Drivers should not change pm_runtime_irq_safe() + * after probe. + */ + WARN_ON(pcdev->irq_safe != pm_runtime_is_irq_safe(dev)); + + if (pcdev->irq_safe) + ret = clk_enable(pcdev->pclk); + else + ret = clk_prepare_enable(pcdev->pclk); /* Failure is probably fatal to the system, but... */ if (ret) return ret; @@ -191,8 +210,10 @@ static int amba_probe(struct device *dev) pm_runtime_enable(dev); ret = pcdrv->probe(pcdev, id); - if (ret == 0) + if (ret == 0) { + pcdev->irq_safe = pm_runtime_is_irq_safe(dev); break; + } pm_runtime_disable(dev); pm_runtime_set_suspended(dev); diff --git a/include/linux/amba/bus.h b/include/linux/amba/bus.h index ad52027a9cbf..ce101e4497d6 100644 --- a/include/linux/amba/bus.h +++ b/include/linux/amba/bus.h @@ -32,6 +32,7 @@ struct amba_device { struct clk *pclk; unsigned int periphid; unsigned int irq[AMBA_NR_IRQS]; + unsigned int irq_safe:1; }; struct amba_driver {
The AMBA bus driver defines runtime Power Management functions which disable and unprepare AMBA bus clock. This is problematic for runtime PM because unpreparing a clock might sleep so it is not interrupt safe. However some drivers may want to implement runtime PM functions in interrupt-safe way (see pm_runtime_irq_safe()). In such case the AMBA bus driver should only disable/enable the clock in runtime suspend and resume callbacks. Detect the device driver behavior after calling its probe function and store it. During runtime suspend/resume deal with clocks according to stored value. Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com> --- drivers/amba/bus.c | 29 +++++++++++++++++++++++++---- include/linux/amba/bus.h | 1 + 2 files changed, 26 insertions(+), 4 deletions(-)