linux-kernel - Re: [PATCH v3 6/6] asus-wmi: Support the hardware GPU MUX on some laptops

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Message-ID: <9ed62983bd03ed26cdb4399dd69b4096e8711fa9.camel@ljones.dev>
Date:   Fri, 12 Aug 2022 10:01:51 +1200
From:   Luke Jones <luke@...nes.dev>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     andy.shevchenko@...il.com, pobrn@...tonmail.com, pavel@....cz,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 6/6] asus-wmi: Support the hardware GPU MUX on some
 laptops

Hi Hans,

On Thu, 2022-08-11 at 15:53 +0200, Hans de Goede wrote:
> Hi,
> 
> On 8/9/22 04:50, Luke D. Jones wrote:
> > Support the hardware GPU MUX switch available on some models. This
> > switch can toggle the MUX between:
> > 
> > - 0, Dedicated mode
> > - 1, Optimus mode
> > 
> > Optimus mode is the regular iGPU + dGPU available, while dedicated
> > mode switches the system to have only the dGPU available.
> > 
> > Signed-off-by: Luke D. Jones <luke@...nes.dev>
> 
> I see that you have replied to this that it needs more work.
> 
> Besides it needing more work, ideally this should hook into
> the existing vga-switcheroo mechanism for this. Can you take
> a look at that please?
> 
> I think this might be the first non GPU driver doing vga-
> switcheroo stuff. So this may be something to discuss
> on the dri-devel list.

I'm not sure how this would work. In typical ASUS fashion they do non-
standard stuff. This switch is a basic toggle that requires a reboot to
enable after writing to the ACPI method, after reboot the dGPU becomes
the only visible GPU on the system and (this GPU) can not be suspended.

In short: it toggles the laptop from discrete-only mode, and optimus
mode, requiring a reboot to switch.

>From what I understand of switcheroo it is more to manage having dual
(or more) GPU available during runtime, and manage the power states,
offload etc.

I have a vastly improved patch for this prepared now. Because of how
the actual feature works (and the above explanation) it must be under
the asus-nb-wmi sysfs (next to the dgpu_disable and egpu_enable toggles
which are also unusual and non-standard work-arounds of Windows
issues).

Kind regards,
Luke.