On Friday, November 07, 2014 09:01:09 AM Krzysztof Kozlowski wrote:
> On czw, 2014-11-06 at 23:52 +0100, Rafael J. Wysocki wrote:
> > On Thursday, November 06, 2014 09:36:48 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 during runtime suspend. During runtime
> > > resume deal with clocks according to stored value.
> > >
> > > Signed-off-by: Krzysztof Kozlowski <k.kozlow...@samsung.com>
> > > ---
> > > drivers/amba/bus.c | 17 +++++++++++++----
> > > include/linux/amba/bus.h | 1 +
> > > 2 files changed, 14 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
> > > index 47bbdc1b5be3..356f906c6966 100644
> > > --- a/drivers/amba/bus.c
> > > +++ b/drivers/amba/bus.c
> > > @@ -95,8 +95,14 @@ 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 = dev->power.irq_safe;
> > > +
> > > + if (pcdev->irq_safe)
> > > + clk_disable(pcdev->pclk);
> > > + else
> > > + clk_disable_unprepare(pcdev->pclk);
> > > + }
> > >
> > > return ret;
> > > }
> > > @@ -107,7 +113,10 @@ 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 +124,7 @@ 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;
> >
> > Why do we need the new flag? Seems redundant to me.
>
> Some poorly written driver could set irq_safe somewhere between suspend
> and resume (e.g. in suspend callback).
It could also modify your bus type irq_safe flag to hide the fact. In my
opinion, it doesn't really help.
Rafael
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