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

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 8/12/22 00:01, Luke Jones wrote:
> 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@ljones.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.

Right, I did not realize this requires a reboot, that would be
something to mention in the Documentation bits accompanying the patch.

This is also a reason why it is good to have the docs update in
the same patch as adding the functionality, because the docs may
help with reviewing.

Anyways I agree that if this requires a reboot then using
the vga switcheroo stuff is not applicable. So we can just go with
a simple(ish) asus-wmi sysfs attribute.

> 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).

Ack, sounds good.

Regards,

Hans