Re: [PATCH] drivers: core: Detach device from power domain on shutdown

[Furquan Shaikh <furquan@google.com>]

On Tue, Jan 12, 2021 at 5:09 AM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
>
> On Tue, Jan 12, 2021 at 01:45:25PM +0100, Rafael J. Wysocki wrote:
> > On Tue, Jan 12, 2021 at 10:55 AM Dmitry Osipenko <digetx@gmail.com> wrote:
> > >
> > > 02.12.2020 00:30, Furquan Shaikh пишет:
> > > > When the system is powered off or rebooted, devices are not detached
> > > > from their PM domain. This results in ACPI PM not being invoked and
> > > > hence PowerResouce _OFF method not being invoked for any of the
> > > > devices. Because the ACPI power resources are not turned off in case
> > > > of poweroff and reboot, it violates the power sequencing requirements
> > > > which impacts the reliability of the devices over the lifetime of the
> > > > platform. This is currently observed on all Chromebooks using ACPI.
> > > >
> > > > In order to solve the above problem, this change detaches a device
> > > > from its PM domain whenever it is shutdown. This action is basically
> > > > analogous to ->remove() from driver model perspective. Detaching the
> > > > device from its PM domain ensures that the ACPI PM gets a chance to
> > > > turn off the power resources for the device thus complying with its
> > > > power sequencing requirements.
> > > >
> > > > Signed-off-by: Furquan Shaikh <furquan@google.com>
> > > > ---
> > > >  drivers/base/core.c | 3 +++
> > > >  1 file changed, 3 insertions(+)
> > > >
> > > > diff --git a/drivers/base/core.c b/drivers/base/core.c
> > > > index d661ada1518f..5823f1d719e1 100644
> > > > --- a/drivers/base/core.c
> > > > +++ b/drivers/base/core.c
> > > > @@ -23,6 +23,7 @@
> > > >  #include <linux/of_device.h>
> > > >  #include <linux/genhd.h>
> > > >  #include <linux/mutex.h>
> > > > +#include <linux/pm_domain.h>
> > > >  #include <linux/pm_runtime.h>
> > > >  #include <linux/netdevice.h>
> > > >  #include <linux/sched/signal.h>
> > > > @@ -4057,6 +4058,8 @@ void device_shutdown(void)
> > > >                       dev->driver->shutdown(dev);
> > > >               }
> > > >
> > > > +             dev_pm_domain_detach(dev, true);
> > > > +
> > > >               device_unlock(dev);
> > > >               if (parent)
> > > >                       device_unlock(parent);
> > > >
> > >
> > > This patch broke system shutdown on NVIDIA Tegra using today's
> > > linux-next because power domain can't be turned off until device drivers
> > > handed control over device resets to the power domain of Power
> > > Management controller on Tegra. This patch introduced the wrong
> > > behaviour, apparently it should be made specific to ACPI only.
> > >
> > > Please fix, thanks in advance.

Sorry about the breakage. I am working on an alternate solution that
Rafael suggested.

> >
> > OK, so Greg please drop it.
>
> Now reverted, thanks.

Thanks Greg!

>
> greg k-h