linux-kernel - Re: [PATCH] ACPI: evaluate

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <201204010923.18330.rjw@sisk.pl>
Date:	Sun, 1 Apr 2012 09:23:18 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Lin Ming <ming.m.lin@...el.com>
Cc:	Aaron Lu <aaron.lu@....com>, Len Brown <lenb@...nel.org>,
	linux-acpi@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Zhang Rui <rui.zhang@...el.com>,
	Andiry Xu <andiry.xu@....com>, Alex He <alex.he@....com>
Subject: Re: [PATCH] ACPI: evaluate _PS3 when entering D3 Cold

Hi,

Sorry for the delayed response, I've been travelling recently.

On Sunday, April 01, 2012, Lin Ming wrote:
> On Sun, 2012-04-01 at 13:56 +0800, Aaron Lu wrote:
> > Hi,
> > 
> > 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 == ACPI_STATE_D3_COLD) {
> > > > +			explicit_set = (ps - 1)->flags.explicit_set;
> > > > +			object_name[3] -= 1;
> > > > +		}
> > > 
> > > I'm not sure whether this works or not.
> > > 
> > > From ACPI spec,
> > > 
> > > _PS3 "is used to put the specific device into its D3hot or D3 state"
> > > 
> > > D3 neither means D3hot nor D3cold. It's an old term before D3hot and
> > > D3cold were introduced.
> > I guess D3 has to mean something, right? :-)

Well, not necessarily.

The problem is what state the _PS3 method puts the device into: D3_hot or
D3_cold.

Unfortunately, as far as I can say, ACPI 4.0 didn't specify any "official"
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 that, but
we _must_ assume it does that in general.

> > Here is the problem, there is no _PR3 in AMD's implementation, just _PS3.
> > And since _S0W evaluates 4, I've to put this device into D3 cold state
> > with _PS3.
> > 
> > And the ACPI does have some words like:
> > 
> > ------
> > Platform/drivers must assume that the device will have power completely
> > removed when the device is place into “D3” via _PS3

Exactly.  What it means is basically "always reinitialize the device from
scratch if you have run _PS3 on it".  And that's what we should do.

> > ------
> > 
> > This is in section 7.2.11: _PR3.
> > 
> > > 
> > > Another problem:
> > > 
> > > With your patch, both D3hot and D3cold will evaluate _PS3, right?
> > > 
> > Yes.
> > 
> > > Will it have problem on AMD platform if you try to put ODD into D3hot
> > > state? _PS3 is evaluated, so it actually enters D3Cold state.
> > 
> > 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 cold(via
> > _PS3).
> 
> But this is the generic code. We can't only consider some special
> device.
> 
> Maybe we need some flag to tell which D3 state _PS3 is used for.

No, please.  As I said above, we need to reinitialize devices that _PS3 was
executed on, which is equivalent to saying that those devices were put into
D3_cold.

The only situation where a device can be put into ACPI D3_hot (which is not
the same as PCI D3_hot, mind you) is when:

(1) There is _PR3 listing some of the device's power resources as "on".
(2) The power resources listed by the _PR3 as "off" are turned off and the
    power resources listed by the _PR3 as "on" are left in the "on" state.

Our generic code should reflect that.

Thanks,
Rafael
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/