On 4 November 2014 13:52, Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx> 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 during runtime suspend. During runtime
> resume deal with clocks according to stored value.
>
> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx>
> ---
> drivers/amba/bus.c | 24 ++++++++++++++++++++----
> include/linux/amba/bus.h | 1 +
> 2 files changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
> index 47bbdc1b5be3..27ec8882ec8e 100644
> --- a/drivers/amba/bus.c
> +++ b/drivers/amba/bus.c
> @@ -85,6 +85,13 @@ static struct device_attribute amba_dev_attrs[] = {
> };
>
> #ifdef CONFIG_PM
> +
> +#ifdef CONFIG_PM_RUNTIME
> +#define get_pm_runtime_irq_safe(dev) ((dev)->power.irq_safe)
> +#else
> +#define get_pm_runtime_irq_safe(dev) 1
No, this doesn't work for those drivers that isn't configured as
irq_safe. The pm_runtime_force_suspend() invoked from the driver's
system PM suspend callback, will expect clocks to be unprepared when
CONFIG_PM_RUNTIME is unset.
To address this issue, in principle we need to know whether the driver
has invoked pm_runtime_irq_safe(), even when CONFIG_PM_RUNTIME is
unset.
This may be solved by the help of PM core:
1) Move the irq_safe member in the struct dev_pm_info, outside the
#ifdef CONFIG_PM_RUNTIME.
2) Let the pm_runtime_irq_safe() function be implemented for CONFIG_PM
instead of CONFIG_PM_RUNTIME.
If the PM core maintainers don't like that approach we can always add
an amba specific wrapper function for pm_runtime_irq_safe() and store
the information needed in the struct amba_device.
Kind regards
Uffe
> +#endif
> +
> /*
> * Hooks to provide runtime PM of the pclk (bus clock). It is safe to
> * enable/disable the bus clock at runtime PM suspend/resume as this
> @@ -95,8 +102,14 @@ 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) {
> + pcdev->irq_safe = get_pm_runtime_irq_safe(dev);
> +
> + if (pcdev->irq_safe)
> + clk_disable(pcdev->pclk);
> + else
> + clk_disable_unprepare(pcdev->pclk);
> + }
>
> return ret;
> }
> @@ -107,7 +120,10 @@ static int amba_pm_runtime_resume(struct device *dev)
> int ret;
>
> if (dev->driver) {
> - ret = clk_prepare_enable(pcdev->pclk);
> + 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;
> @@ -115,7 +131,7 @@ static int amba_pm_runtime_resume(struct device *dev)
>
> return pm_generic_runtime_resume(dev);
> }
> -#endif
> +#endif /* CONFIG_PM */
>
> static const struct dev_pm_ops amba_pm = {
> .suspend = pm_generic_suspend,
> 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 {
> --
> 1.9.1
>
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