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

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Date:   Sun, 14 Aug 2022 12:42:10 +0200
From:   Lukas Wunner <lukas@...ner.de>
To:     Luke Jones <luke@...nes.dev>
Cc:     hdegoede@...hat.com, markgross@...nel.org,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] asus-wmi: Support the hardware GPU MUX on some laptops

On Sun, Aug 14, 2022 at 09:09:43PM +1200, Luke Jones wrote:
> On Sat, 2022-08-13 at 12:55 +0200, Lukas Wunner wrote:
> > On Sat, Aug 13, 2022 at 09:26:24PM +1200, 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.
> > 
> > Could you please integrate this with the framework provided by:
> > 
> >   include/linux/vga_switcheroo.h
> >   drivers/gpu/vga/vga_switcheroo.c
> > 
> > vga_switcheroo will then automatically expose a sysfs interface.
> 
> I did investigate this first before submitting. The way asus does it is
> not standard at all. On switch you must reboot, and the change isn't
> reflected by the ACPI get method until reboot. It's very reflective of
> how they used dgpu_disable to work around windows issues that we do in
> Linux by removing the device from the device tree.
> 
> The key thing is a reboot is required. This is not done on-the-fly. I
> have a two year old GX502 which has the same method as exposed here,
> and also a 2022 TUF laptop with same method. My understanding of this
> pariicular method is that it isn't the same one as what Nvidia is
> advertising, and ASUS is perhaps misadvertising it - the suspision is
> raised by the fact that my GX502 machine predates what Nvidia is
> advertising.

I see, thanks for the explanation.  You may want to add that
background information to the commit message if/when respinning.
Indeed vga_switcheroo facilitates GPU switching at runtime,
not upon next reboot.

Thanks,

Lukas