Explicitly putting a PCI device to ACPI D0

Explicitly putting a PCI device to ACPI D0

[Michal Witkowski]

Hi,

I've been searching for my answer for a while now, and since I haven't found it anywhere, 
I've decided to post to LKML, hoping that someone here can help me.

First, I'll explain the background of my problem. My grief is the switchable GPU in my 
Lenovo Ideapad U330. The BIOS supports two options "Discrete only" (only the ATI card is 
visible on the BUS) and "Switchable" (both ATI and Intel card visible on the bus). The 
problem is the lack of a third option "Integrated", in which only the Intel card would be 
powered off. Lenovo refused to introduce such an option into the BIOS, stating that it's a 
feature request and not a bug.

To save battery power I'd like to be able to run on the Intel card. However, with the 
"Switchable" option, powertop indicates huge power usage (24W), which can only be 
explained by the fact that both cards draw power.

Thus, my question is the following:
Is there a way to explicitly put a device into ACPI D0? I would like to do that to the ATI 
card on boot.

I've tried the following code:
http://ftp.chg.ru/pub/parallel/scyld/diag/pci-config.c
But it didn't work (the ATI card was still on).

Cheers,
Michal

Re: Explicitly putting a PCI device to ACPI D0

[Jesse Barnes]

On Wed, 16 Sep 2009 09:10:24 +0200
Michal Witkowski <neuro@o2.pl> wrote:

> Hi,
> 
> I've been searching for my answer for a while now, and since I
> haven't found it anywhere, I've decided to post to LKML, hoping that
> someone here can help me.
> 
> First, I'll explain the background of my problem. My grief is the
> switchable GPU in my Lenovo Ideapad U330. The BIOS supports two
> options "Discrete only" (only the ATI card is visible on the BUS) and
> "Switchable" (both ATI and Intel card visible on the bus). The
> problem is the lack of a third option "Integrated", in which only the
> Intel card would be powered off. Lenovo refused to introduce such an
> option into the BIOS, stating that it's a feature request and not a
> bug.
> 
> To save battery power I'd like to be able to run on the Intel card.
> However, with the "Switchable" option, powertop indicates huge power
> usage (24W), which can only be explained by the fact that both cards
> draw power.
> 
> Thus, my question is the following:
> Is there a way to explicitly put a device into ACPI D0? I would like
> to do that to the ATI card on boot.
> 
> I've tried the following code:
> http://ftp.chg.ru/pub/parallel/scyld/diag/pci-config.c
> But it didn't work (the ATI card was still on).

Your best bet might be to load a driver for the ATI card that puts it
into PCI D3 state until used.  There may be other ways to save power on
the disabled part as well...

Alex, is this something you've looked at at all?

-- 
Jesse Barnes, Intel Open Source Technology Center

Re: Explicitly putting a PCI device to ACPI D0

[Alex Deucher]

On Wed, Sep 16, 2009 at 12:09 PM, Jesse Barnes <jbarnes@virtuousgeek.org> wrote:
> On Wed, 16 Sep 2009 09:10:24 +0200
> Michal Witkowski <neuro@o2.pl> wrote:
>
>> Hi,
>>
>> I've been searching for my answer for a while now, and since I
>> haven't found it anywhere, I've decided to post to LKML, hoping that
>> someone here can help me.
>>
>> First, I'll explain the background of my problem. My grief is the
>> switchable GPU in my Lenovo Ideapad U330. The BIOS supports two
>> options "Discrete only" (only the ATI card is visible on the BUS) and
>> "Switchable" (both ATI and Intel card visible on the bus). The
>> problem is the lack of a third option "Integrated", in which only the
>> Intel card would be powered off. Lenovo refused to introduce such an
>> option into the BIOS, stating that it's a feature request and not a
>> bug.
>>
>> To save battery power I'd like to be able to run on the Intel card.
>> However, with the "Switchable" option, powertop indicates huge power
>> usage (24W), which can only be explained by the fact that both cards
>> draw power.
>>
>> Thus, my question is the following:
>> Is there a way to explicitly put a device into ACPI D0? I would like
>> to do that to the ATI card on boot.
>>
>> I've tried the following code:
>> http://ftp.chg.ru/pub/parallel/scyld/diag/pci-config.c
>> But it didn't work (the ATI card was still on).
>
> Your best bet might be to load a driver for the ATI card that puts it
> into PCI D3 state until used.  There may be other ways to save power on
> the disabled part as well...
>
> Alex, is this something you've looked at at all?

The xf86-video-ati ddx can turn off the displays and reduce the clocks
and pcie lanes, but I haven't sorted out all the D3 stuff yet.  As for
the switchable graphics, you might find the page below useful.  No
idea if it will work or fry your hardware:
http://ubuntuforums.org/showthread.php?p=7944950

Alex

Re: Explicitly putting a PCI device to ACPI D0

[Michal Witkowski]

On Wednesday 16 of September 2009 18:33:58 you wrote:
> The xf86-video-ati ddx can turn off the displays and reduce the clocks
> and pcie lanes, but I haven't sorted out all the D3 stuff yet.  As for
> the switchable graphics, you might find the page below useful.  No
> idea if it will work or fry your hardware:
> http://ubuntuforums.org/showthread.php?p=7944950
> 
> Alex
> 

Thank you very very much :)
The above kernel module worked wonders for me.

Cheers,
Michal