From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aaron Lu Subject: Re: [PATCH] ACPI: evaluate _PS3 when entering D3 Cold Date: Sun, 1 Apr 2012 23:34:35 +0800 Message-ID: <20120401153434.GA3268@localhost.amd.com> References: <1333217910-29579-1-git-send-email-aaron.lu@amd.com> <1333258053.2939.22.camel@minggr> <20120401055603.GA11505@localhost.amd.com> <1333263819.2387.94.camel@rui.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <1333263819.2387.94.camel@rui.sh.intel.com> Sender: linux-kernel-owner@vger.kernel.org To: Zhang Rui Cc: Lin Ming , Len Brown , "Rafeal J. Wysocki" , linux-acpi@vger.kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Andiry Xu , Alex He List-Id: linux-acpi@vger.kernel.org Hi, On Sun, Apr 01, 2012 at 03:03:39PM +0800, Zhang Rui wrote: > First of all, I agree that we must evaluate _PS3 when setting device = to > either D3_HOT or D3_COLD. Good. >=20 > And here is my understanding about D3/D3_HOT/D3_COLD, >=20 > if _PR3 exists, it means the devices supports both D3_HOT and D3_COLD= =2E Agree. >=20 > if only _PS3 exists, we can only say that the state after evaluating > _PS3 is D3, it could either be D3_HOT or D3_COLD, and this is device > specific, which in your case, is D3_COLD. I prefer Rafeal's definition, let's just *assume* the device is at D3 cold after its _PS3 is executed. Unless it has _PR3, in which case, we have a chance to put the device into D3 hot instead. >=20 > BTW, here is the description of _S0W in ACPI spec, > If OSPM has not indicated that it supports _PR3 through the OSPM > Platform-Wide Capabilities (see Section 6.2.10.2), then the value "3" > corresponds to D3. If it has indicated _PR3 support, the value "3" > represents D3hot and the value "4" represents D3cold. >=20 > So IMO, the _S0W should return 3 in AMD's implementation as it does n= ot > have _PR3. OK, sounds like a firmware bug. Thanks for identifying this. >=20 > > And the ACPI does have some words like: > >=20 > > ------ > > Platform/drivers must assume that the device will have power comple= tely > > removed when the device is place into =E2=80=9CD3=E2=80=9D via _PS3 > > ------ > >=20 > I think this means OS can not access device any more after evaluating > _PS3, and it should re-enumerate the device when transiting back to D= 0. >=20 > > This is in section 7.2.11: _PR3. > >=20 > > >=20 > > > Another problem: > > >=20 > > > With your patch, both D3hot and D3cold will evaluate _PS3, right? > > >=20 > > Yes. > >=20 > > > Will it have problem on AMD platform if you try to put ODD into D= 3hot > > > state? _PS3 is evaluated, so it actually enters D3Cold state. > >=20 > > There is no D3 hot support for this device(from the firmware's > > perspective), either it is at D0(via _PS0), or it will be at D3 col= d(via > > _PS3). > >=20 > I was trying to make a cleanup of the D3/D3_HOT/D3_COLD support in > Linux, and this gives me some clue. This is great, and I would like to help as much as I can. >=20 > How about this? >=20 > We should use the term "D3" in general in Linux. > Without _PR3, OS should *assume* that the power is removed, although = it > may be not true. > With _PR3, OS can *assure* that the power is removed, because it know= s > how to remove thw power (evaluating _PR3._OFF). >=20 > So the difference is that OS need to make sure whether to evaluate > _PR3._OFF when _PR3 exists. For example, a device has _PR3, but _S0W > returns 3, OS should not evaluate _PR3._OFF when the device sleeps wi= th > remote wakeup support. >=20 > what do you think? I agree with Rafeal's ideas. -Aaron