linux-kernel - Re: [PATCH 1/4] ACPI / PM: Make acpi_bus_init

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Date:	Tue, 22 Jan 2013 09:10:56 +0200
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Lv Zheng <lv.zheng@...el.com>
Subject: Re: [PATCH 1/4] ACPI / PM: Make acpi_bus_init_power() more robust

On Tue, Jan 22, 2013 at 03:09:01AM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> The ACPI specification requires the _PSC method to be present under
> a device object if its power state cannot be inferred from the states
> of power resources used by it (ACPI 5, Section 7.6.2).  However, it
> also requires that (for power states D0-D2 and D3hot) if the _PSn
> (n = 0, 1, 2, 3) method is present under the device object, it also
> must be executed after the power resources have been set
> appropriately for the device to go into power state Dn (D3 means
> D3hot in this case).  Thus it is not clear from the specification
> whether or not the _PSn method should be executed if the initial
> configuraion of power resources used by the device indicates power
> state Dn and the _PSC method is not present.
> 
> The current implementation of acpi_bus_init_power() is based on the
> assumption that it should not be necessary to execute _PSn in the
> above situation, but experience shows that in fact that assumption
> need not be satisfied.  For this reason, make acpi_bus_init_power()
> always execute _PSn if the initial configuration of device power
> resources indicates power state Dn.
> 
> Reported-by: Mika Westerberg <mika.westerberg@...ux.intel.com>

You can add also,

Tested-by: Mika Westerberg <mika.westerberg@...ux.intel.com>

if you like. Thanks for fixing this.
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