On 16 September 2014 14:59, 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 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>
> ---
> 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
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