From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: [PATCH] ACPI: evaluate _PS3 when entering D3 Cold Date: Sun, 1 Apr 2012 10:49:08 +0200 Message-ID: <201204011049.08609.rjw@sisk.pl> References: <1333217910-29579-1-git-send-email-aaron.lu@amd.com> <201204010923.18330.rjw@sisk.pl> <1333266346.2387.110.camel@rui.sh.intel.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from ogre.sisk.pl ([217.79.144.158]:47681 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751894Ab2DAIot convert rfc822-to-8bit (ORCPT ); Sun, 1 Apr 2012 04:44:49 -0400 In-Reply-To: <1333266346.2387.110.camel@rui.sh.intel.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Zhang Rui Cc: Lin Ming , Aaron Lu , Len Brown , linux-acpi@vger.kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Andiry Xu , Alex He On Sunday, April 01, 2012, Zhang Rui wrote: > On =E6=97=A5, 2012-04-01 at 09:23 +0200, Rafael J. Wysocki wrote: > > Hi, > >=20 > > Sorry for the delayed response, I've been travelling recently. > >=20 > > On Sunday, April 01, 2012, Lin Ming wrote: > > > On Sun, 2012-04-01 at 13:56 +0800, Aaron Lu wrote: > > > > Hi, > > > >=20 > > > > On Sun, Apr 01, 2012 at 01:27:33PM +0800, Lin Ming wrote: > > > > > > - if (device->power.states[state].flags.explicit_set) { > > > > > > + /* If state is D3 Cold, try to evaluate _PS3 first */ > > > > > > + if (state =3D=3D ACPI_STATE_D3_COLD) { > > > > > > + explicit_set =3D (ps - 1)->flags.explicit_set; > > > > > > + object_name[3] -=3D 1; > > > > > > + } > > > > >=20 > > > > > I'm not sure whether this works or not. > > > > >=20 > > > > > From ACPI spec, > > > > >=20 > > > > > _PS3 "is used to put the specific device into its D3hot or D3= state" > > > > >=20 > > > > > D3 neither means D3hot nor D3cold. It's an old term before D3= hot and > > > > > D3cold were introduced. > > > > I guess D3 has to mean something, right? :-) > >=20 > > Well, not necessarily. > >=20 > > The problem is what state the _PS3 method puts the device into: D3_= hot or > > D3_cold. > >=20 > > Unfortunately, as far as I can say, ACPI 4.0 didn't specify any "of= ficial" > > mapping between the "old" D3 and the "new" D3_{hod|cold} states, so= we need to > > figure out something. In my opinion, the only reasonable approach = is to > > assume that the state _PS3 puts the device into is always D3_cold, = becuase > > _PS3 may remove power completely from the device. It may not do th= at, but > > we _must_ assume it does that in general. > >=20 > There is a problem that I can think of. > Say currently, ACPI always returns D3 when _PS3 exists. I'm not sure what you mean exactly, but please see below. > And this "ACPI_STATE_D3" is translated to PCI_D3hot. > But with this approach, we're going to put these devices to PCI_D3col= d > instead, right? > I'm not against this approach, but this may affect a lot of PCI devic= es, > which we need to take care of, no? Do you mean acpi_pm_device_sleep_state() should be modified? It doesn'= t refer to whether or not _PS3 exists, as far as I can say. In the acpi_pci_set_power_state() code path, on the other hand, there a= re two potentially problematic situations when PCI wants to put the device= into PCI_D3hot (which need not map 1:1 onto ACPI D3_hot), one of which is wh= en _PS3 is present, and the other is when neither _PS3, nor _PR3 is present. If _PS3 is present, then _PR3 may or may not be present. In the latter= case we can only execute _PS3 in the hope it does the right thing, but as lo= ng as we restore the device's configuration registers while resuming it (w= hich is done by all of our PCI device resume callback routines as far as I can = say), the only possible difference is the resume latency (which may be greate= r if power is removed from the device entirely). However, in that case we s= houldn't turn off the device's power resources after _PS3 has been executed (if = we turned them off, power would be removed from the device, which wouldn't= be what PCI wanted). So, to handle this particular case we need to pass ACPI_STATE_D3_HOT to acpi_bus_set_power(), meaning "avoid going into D3= _cold, if possible". In both _PS3 and _PR3 are present, we should evaluate _PS3 and then tur= n off the power resources listed as "off" by _PR3 (and turn on the power reso= ruces listed by it as "on"), but we need to restore the configuration registe= rs of the device while resuming it. I think this is handled correctly withou= t modifications. If neither _PS3 nor _PR3 is present, we shouldn't turn off the device's power resources, because PCI doesn't want power to be removed from the = device. In summary, if PCI wants the device to be put into PCI_D3hot and _PS3 i= s present, we should evaluate _PS3. However, we shouldn't turn the devic= e's power resources off unless _PR3 is present, in which case we can turn o= ff the power resources listed by it as "off". Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html