[RFC PATCH 9/9] drm/amdgpu: register a vga_switcheroo client for all GPUs that are not thunderbolt attached

[Alex Deucher]

On Fri, Feb 10, 2023 at 11:07 AM Hans de Goede <hdegoede at redhat.com> wrote:
>
> Hi,
>
> On 2/10/23 16:53, Alex Deucher wrote:
> > On Fri, Feb 10, 2023 at 3:04 AM Orlando Chamberlain
> > <orlandoch.dev at gmail.com> wrote:
> >>
> >> From: Kerem Karabay <kekrby at gmail.com>
> >>
> >> Commit 3840c5bcc245 ("drm/amdgpu: disentangle runtime pm and
> >> vga_switcheroo") made amdgpu only register a vga_switcheroo client for
> >> GPU's with PX, however AMD GPUs in dual gpu Apple Macbooks do need to
> >> register, but don't have PX. Instead of AMD's PX, they use apple-gmux.
> >
> > Is there a way to detect apple-gmux instead?  Otherwise, we register
> > vga_switcheroo on any system with multiple GPUs which is not what we
> > want.
>
> Yes since 6.1.y (either stable series or just take 6.2.0) the apple-gmux
> detect code has been factored out into a stand-alone
> apple_gmux_detect() helper inside:
>
> include/linux/apple-gmux.h
>
> For usage outside of the actual apple-gmux driver you can simply
> pass NULL for both arguments.
>
> This was necessary to reliably check if the apple-gmux should be
> used for backlight control.
>
> Note there also is the older apple_gmux_present() helper, which is
> already used in some drm code. That function is not reliable though
> it detects if the ACPI tables contain an ACPI device describing
> the presence of a gmux, but it turns out even Apple has buggy ACPI
> tables and the mere presence of that ACPI device is not a reliable
> indicator the gmux is actually there.
>
> I have not changed over any of the existing apple_gmux_present()
> users for fear of unwanted side effects...

Looks like we could maybe use the PWRD ACPI check like patch 8 does as well.

Alex

>
> Regards,
>
> Hans
>
>
>
>
> >> Revert to the old logic of registering for all non-thunderbolt gpus,
> >> like radeon and nouveau.
> >>
> >> Fixes: 3840c5bcc245 ("drm/amdgpu: disentangle runtime pm and vga_switcheroo")
> >> Signed-off-by: Kerem Karabay <kekrby at gmail.com>
> >> [Orlando Chamberlain <orlandoch.dev at gmail.com>: add commit description]
> >> Signed-off-by: Orlando Chamberlain <orlandoch.dev at gmail.com>
> >> ---
> >>  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 18 +++++++++++-------
> >>  1 file changed, 11 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> >> index 2f28a8c02f64..0bb553a61552 100644
> >> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> >> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> >> @@ -3919,12 +3919,13 @@ int amdgpu_device_init(struct amdgpu_device *adev,
> >>         if ((adev->pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA)
> >>                 vga_client_register(adev->pdev, amdgpu_device_vga_set_decode);
> >>
> >> -       if (amdgpu_device_supports_px(ddev)) {
> >> -               px = true;
> >> -               vga_switcheroo_register_client(adev->pdev,
> >> -                                              &amdgpu_switcheroo_ops, px);
> >> +       px = amdgpu_device_supports_px(ddev);
> >> +
> >> +       if (!pci_is_thunderbolt_attached(adev->pdev))
> >> +               vga_switcheroo_register_client(adev->pdev, &amdgpu_switcheroo_ops, px);
> >> +
> >> +       if (px)
> >>                 vga_switcheroo_init_domain_pm_ops(adev->dev, &adev->vga_pm_domain);
> >> -       }
> >>
> >>         if (adev->gmc.xgmi.pending_reset)
> >>                 queue_delayed_work(system_wq, &mgpu_info.delayed_reset_work,
> >> @@ -4048,10 +4049,13 @@ void amdgpu_device_fini_sw(struct amdgpu_device *adev)
> >>
> >>         kfree(adev->bios);
> >>         adev->bios = NULL;
> >> -       if (amdgpu_device_supports_px(adev_to_drm(adev))) {
> >> +
> >> +       if (!pci_is_thunderbolt_attached(adev->pdev))
> >>                 vga_switcheroo_unregister_client(adev->pdev);
> >> +
> >> +       if (amdgpu_device_supports_px(adev_to_drm(adev)))
> >>                 vga_switcheroo_fini_domain_pm_ops(adev->dev);
> >> -       }
> >> +
> >>         if ((adev->pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA)
> >>                 vga_client_unregister(adev->pdev);
> >>
> >> --
> >> 2.39.1
> >>
> >
>