On Monday, October 20, 2014 11:04:46 AM Krzysztof Kozlowski 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@xxxxxxxxxxx>
> Reviewed-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> ---
> 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 47bbdc1b5be3..474434e1b1b9 100644
> --- a/drivers/amba/bus.c
> +++ b/drivers/amba/bus.c
> @@ -95,8 +95,18 @@ 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;
> }
> @@ -107,7 +117,16 @@ 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;
> @@ -198,8 +217,10 @@ 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);
This looks racy.
Is it guaranteed that runtime PM callbacks won't be run for the device
after pcdrv->probe() has returned and before setting pcdev->irq_safe?
If not, inconsistent behavior may ensue.
> 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 ac02f9bd63dc..c4bae79851fb 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 {
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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