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

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Date:   Tue, 12 Jan 2021 12:55:38 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Furquan Shaikh <furquan@...gle.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH] drivers: core: Detach device from power domain on
 shutdown

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@...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);
> 

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.