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

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Message-ID: <X/h9+1YUj49qQcil@kroah.com>
Date:   Fri, 8 Jan 2021 16:44:59 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Furquan Shaikh <furquan@...gle.com>
Cc:     "Rafael J . Wysocki" <rafael@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH] drivers: core: Detach device from power domain on
 shutdown

On Mon, Dec 14, 2020 at 08:56:48PM -0800, Furquan Shaikh wrote:
> On Tue, Dec 1, 2020 at 1:30 PM Furquan Shaikh <furquan@...gle.com> wrote:
> >
> > 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@...gle.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);
> > --
> > 2.29.2.454.gaff20da3a2-goog
> >
> 
> Hello,
> 
> Gentle ping. Just checking if there are any comments.

I'll wait for Rafael to ack this before taking it...

thanks,

greg k-h