On Tue, Sep 16, 2014 at 08:25:25PM +0200, Ulf Hansson wrote:
> 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!?
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.
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