linux-kernel - Re: [PATCH] sky2: override for PCI legacy power management

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Message-ID: <CAErSpo7J+9ZgXcqw4_+WjpNAW9oKNfRosDm7CusUjpnukO1m4Q@mail.gmail.com>
Date:	Wed, 21 Mar 2012 14:54:05 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	Knut Petersen <Knut_Petersen@...nline.de>,
	"David S. Miller" <davem@...emloft.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>, arekm@...en.pl,
	Jared <nitro@...room.net>, dilieto@...eone.net,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] sky2: override for PCI legacy power management

On Wed, Mar 21, 2012 at 2:47 PM, Stephen Hemminger
<shemminger@...tta.com> wrote:
> On Wed, 21 Mar 2012 14:22:01 -0600
> Bjorn Helgaas <bhelgaas@...gle.com> wrote:
>
>> On Wed, Mar 21, 2012 at 9:32 AM, Stephen Hemminger
>> <shemminger@...tta.com> wrote:
>> > Some BIOS's don't setup power management correctly (what else is
>> > new) and don't allow use of PCI Express power control. Add a special
>> > exception module parameter to allow working around this issue.
>> > Based on slightly different patch by Knut Petersen.
>> >
>> > Reported-by: Arkadiusz Miskiewicz <arekm@...en.pl>
>> > Signed-off-by: Stephen Hemminger <shemminger@...tta.com>
>>
>> Is there a problem report URL you can include here?
>>
>> It looks like this requires a user to figure out that he might be
>> suffering from this problem, then use this module parameter to work
>> around it.  How would a user figure that out?  Can we do it
>> automatically to save him the trouble?
>
> I am not a power management expert. Looks like a BIOS issue where the
> BIOS has configured the device to disable power management but the
> user wants to override that value. There is no method to determine
> when the BIOS is broken versus when the BIOS setting is correct and
> we should follow what it says.

I'm not a power management expert either.  I was just wondering
whether the known broken BIOSes could be encoded in a blacklist or
something, because it looks like a case where a user might have to
request help or debug the problem again before discovering this flag.

Bjorn
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