[PATCH] drm/amdgpu: don't call drm_fb_helper_lastclose in lastclose()

[Alex Deucher]

On Mon, Oct 24, 2022 at 3:33 AM Thomas Zimmermann <tzimmermann at suse.de> wrote:
>
> Hi
>
> Am 24.10.22 um 08:20 schrieb Quan, Evan:
> > [AMD Official Use Only - General]
> >
> > Reviewed-by: Evan Quan <evan.quan at amd.com>
> >
> >> -----Original Message-----
> >> From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of Alex
> >> Deucher
> >> Sent: Thursday, October 20, 2022 10:36 PM
> >> To: amd-gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org
> >> Cc: Deucher, Alexander <Alexander.Deucher at amd.com>; Thomas
> >> Zimmermann <tzimmermann at suse.de>
> >> Subject: [PATCH] drm/amdgpu: don't call drm_fb_helper_lastclose in
> >> lastclose()
> >>
> >> It's used to restore the fbdev console, but as amdgpu uses
> >> generic fbdev emulation, the console is being restored by the
> >> DRM client helpers already. See the call to drm_client_dev_restore()
> >> in drm_lastclose().
> >>
> >> Fixes: 087451f372bf76 ("drm/amdgpu: use generic fb helpers instead of
> >> setting up AMD own's.")
> >> Cc: Thomas Zimmermann <tzimmermann at suse.de>
> >> Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
> >> ---
> >>   drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c | 1 -
> >>   1 file changed, 1 deletion(-)
> >>
> >> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
> >> b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
> >> index fe23e09eec98..474b9f40f792 100644
> >> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
> >> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
> >> @@ -1106,7 +1106,6 @@ int amdgpu_info_ioctl(struct drm_device *dev,
> >> void *data, struct drm_file *filp)
> >>    */
> >>   void amdgpu_driver_lastclose_kms(struct drm_device *dev)
> >>   {
> >> -    drm_fb_helper_lastclose(dev);
> >>      vga_switcheroo_process_delayed_switch();
> >>   }
>
> Without the call to drm_fb_helper_lastclose(), the console emulation
> will be restored by drm_client_dev_restore() from drm_lastclose(). [1]
> It means that it's now changing order with the call to
> vga_switcheroo_process_delay_switch(). Can this become a problem?
>
> I looked at the other callers of that function. Most restore the console
> before doing the switcheroo. Nouveau doesn't seem to care about the
> console at all.

I don't know off hand.  I suppose if the switch powered down the GPU
and then we tried to restore it's console state that would be a
problem, but it looks like vga_switchto_stage2() just powers down the
GPU without going through suspend so I'm not sure if this actually
worked correctly?  What are the potential problems with calling
drm_fb_helper_lastclose twice?

Alex

>
> Best regards
> Thomas
>
> [1]
> https://elixir.bootlin.com/linux/v6.0.3/source/drivers/gpu/drm/drm_file.c#L467
>
> >>
> >> --
> >> 2.37.3
>
> --
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Maxfeldstr. 5, 90409 Nürnberg, Germany
> (HRB 36809, AG Nürnberg)
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