[PATCH] drm/amdgpu: always reset asic when going into suspend

[Alex Deucher]

On Wed, Oct 16, 2019 at 3:24 AM Daniel Drake <drake at endlessm.com> wrote:
>
> On Wed, Oct 16, 2019 at 2:43 AM Alex Deucher <alexdeucher at gmail.com> wrote:
> > Is s2idle actually powering down the GPU?
>
> My understanding is that s2idle (at a high level) just calls all
> devices suspend routines and then puts the CPU into its deepest
> running state.
> So if there is something special to be done to power off the GPU, I
> believe that amdgpu is responsible for making arrangements for that to
> happen.
> In this case the amdgpu code already does:
>
>         pci_disable_device(dev->pdev);
>         pci_set_power_state(dev->pdev, PCI_D3hot);
>
> And the PCI layer will call through to any appropriate ACPI methods
> related to that low power state.
>
> > Do you see a difference in power usage?  I think you are just working around the fact that the
> > GPU never actually gets powered down.
>
> I ran a series of experiments.
>
> Base setup: no UI running, ran "setterm -powersave 1; setterm -blank
> 1" and waited 1 minute for screen to turn off.
> Base power usage in this state is 4.7W as reported by BAT0/power_now
>
> 1. Run amdgpu_device_suspend(ddev, true, true); before my change
> --> Power usage increases to 6.1W
>
> 2. Run amdgpu_device_suspend(ddev, true, true); with my change applied
> --> Power usage increases to 6.0W
>
> 3. Put amdgpu device in runtime suspend
> --> Power usage increases to 6.2W
>
> 4. Try unmodified suspend path but d3cold instead of d3hot
> --> Power usage increases to 6.1W
>
> So, all of the suspend schemes actually increase the power usage by
> roughly the same amount, reset or not, with and without my patch :/
> Any ideas?

Do these patches help?
https://patchwork.freedesktop.org/patch/341775/
https://patchwork.freedesktop.org/patch/341968/

Alex

>
> Thanks,
> Daniel