From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aaron Lu Subject: Re: [PATCH] ACPI / PM: Infer parent power state from child if unknown, v2 Date: Wed, 12 Sep 2012 14:59:04 +0800 Message-ID: <20120912065902.GA2229@mint-spring.sh.intel.com> References: <1346053126-7646-1-git-send-email-aaron.lu@intel.com> <201209102150.22738.rjw@sisk.pl> <20120911053305.GA2130@mint-spring.sh.intel.com> <201209112238.06658.rjw@sisk.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mga14.intel.com ([143.182.124.37]:48738 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750726Ab2ILG7H (ORCPT ); Wed, 12 Sep 2012 02:59:07 -0400 Content-Disposition: inline In-Reply-To: <201209112238.06658.rjw@sisk.pl> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: "Rafael J. Wysocki" Cc: Len Brown , linux-acpi@vger.kernel.org, linux-pm@vger.kernel.org, Aaron Lu , LKML On Tue, Sep 11, 2012 at 10:38:06PM +0200, Rafael J. Wysocki wrote: > It turns out that there are ACPI BIOSes defining device objects with > _PSx and without either _PSC or _PRx. For devices corresponding to > those ACPI objetcs __acpi_bus_get_power() returns ACPI_STATE_UNKNOWN > and their initial power states are regarded as unknown as a result. > If such a device is a parent of another power-manageable device, the > child cannot be put into a low-power state through ACPI, because > __acpi_bus_set_power() refuses to change power states of devices > whose parents' power states are unknown. > > To work around this problem, observe that the ACPI power state of > a device cannot be higher-power (lower-number) than the power state > of its parent. Thus, if the device's _PSC method or the > configuration of its power resources indicates that the device is > in D0, the device's parent has to be in D0 as well. Consequently, > if the parent's power state is unknown when we've just learned that > its child's power state is D0, we can safely set the parent's > power.state field to ACPI_STATE_D0. > > Signed-off-by: Rafael J. Wysocki Tested-by: Aaron Lu -Aaron > --- > drivers/acpi/bus.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > Index: linux/drivers/acpi/bus.c > =================================================================== > --- linux.orig/drivers/acpi/bus.c > +++ linux/drivers/acpi/bus.c > @@ -237,6 +237,16 @@ static int __acpi_bus_get_power(struct a > } else if (result == ACPI_STATE_D3_HOT) { > result = ACPI_STATE_D3; > } > + > + /* > + * If we were unsure about the device parent's power state up to this > + * point, the fact that the device is in D0 implies that the parent has > + * to be in D0 too. > + */ > + if (device->parent && device->parent->power.state == ACPI_STATE_UNKNOWN > + && result == ACPI_STATE_D0) > + device->parent->power.state = ACPI_STATE_D0; > + > *state = result; > > out: