[PATCH v2 1/4] PM / Domains: Remove pm_genpd_dev_need_restore() API

[Ulf Hansson]

On 1 October 2014 18:36, Sylwester Nawrocki <s.nawrocki at samsung.com> wrote:
> On 01/10/14 16:41, Ulf Hansson wrote:
>> There are currently no users of this API, let's remove it.

Hi Sylwester,

Thanks for your reply!

>
> The sad fact is that removal of pm_genpd_dev_need_restore() calls
> from arch/arm/mach-exynos/pm_domains.c introduces regressions in
> multiple exynos drivers (I'm sure it breaks media drivers).

The fact that you need pm_genpd_dev_need_restore() is really worrying.
That indicates that exynos are suffering from this race condition I am
trying to fix in this patchset.

> I think before doing such changes all relevant drivers should be
> updated first. I need to take a closer look again, but it seems
> after dropping the pm_genpd_dev_need_restore() calls, client
> driver's runtime_resume() callback is not being called in response
> to first pm_runtime_get(_sync) call, even if a device is runtime
> pm active.

Why would runtime PM callbacks be invoked when the device are runtime
PM active? That's prevented by the runtime PM core and is the expected
behaviour.

pm_genpd_dev_need_restore() is not the solution, besides that it gives
you the option to lie about device's runtime PM state to genpd. Thus,
if you are really lucky, that might workaround your issues. :-)

I will happily help out in fixing drivers for exynos. Would be nice if
you could provide me with a list of which driver/subsystems that seems
broken. HW, wise I have a exynos 5250 and exynos 5422 on my desk, so
those I can test.

>
> More details can be found in commit ebc35c726298ba3fdebba316a
> 'ARM: EXYNOS: register devices in 'need_restore' state for pm_domains'.
>
> The above only happens when devices are added to an inactive power
> domain, then I guess patch 2/4 is also an attempt to address this
> issue ?

Yes.

I would really appreciate if you could run a test with the complete
patchset and see if that resolves the issues.

Kind regards
Uffe