linux-kernel - Re: [PATCH] ACPI / PM: Use target_state to set the device power state

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Message-ID: <6917556.GA7pjcvNI8@vostro.rjw.lan>
Date:	Tue, 28 Jul 2015 17:59:38 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ACPI / PM: Use target_state to set the device power state

On Tuesday, July 28, 2015 01:51:21 PM Mika Westerberg wrote:
> Commit 20dacb71ad28 ("ACPI / PM: Rework device power management to follow
> ACPI 6") changed the device power management to use D3hot if the device
> in question does not have _PR3 method even if D3cold was requested by the
> caller.
> 
> However, if the device has _PR3 device->power.state is also set to D3hot
> instead of D3Cold after power resources have been turned off because
> device->power.state will be assigned from "state" instead of
> "target_state".
> 
> Next time the device is transitioned to D0, acpi_power_transition() will
> find that the current power state of the device is D3hot instead of D3cold
> which causes it to power down all resources required for the current
> (wrong) state D3hot.
> 
> Below is a simplified ASL example of a real touch panel device which
> triggers the problem:
> 
>   Scope (TPL1)
>   {
>       Name (_PR0, Package (1) { \_SB.PCI0.I2C1.PXTC })
>       Name (_PR3, Package (1) { \_SB.PCI0.I2C1.PXTC })
>       ...
>   }
> 
> In both D0 and D3hot the same power resource is required. However, when
> acpi_power_transition() turns off power resources required for D3hot (as
> the device is transitioned to D0) it powers down PXTC which then makes the
> device to lose its power.
> 
> Fix this by assigning "target_state" to the device power state instead of
> "state" that is always D3hot even for devices with valid _PR3.
> 
> Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>

Applied, thanks!

Rafael

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