Re: amdgpu_dm_connector_mode_valid regression

[Gergo Koteles <soyer@irl.hu>]

Hi Dmitry,

On Wed, 2025-04-02 at 17:40 +0300, Dmitry Baryshkov wrote:
> On Wed, 2 Apr 2025 at 17:35, Gergo Koteles <soyer@irl.hu> wrote:
> > 
> > Hi Dmitry,
> > 
> > On Wed, 2025-04-02 at 16:36 +0300, Dmitry Baryshkov wrote:
> > > > > 
> > > > > It works if I call
> > > > > drm_mode_set_crtcinfo((struct drm_display_mode *)mode, 0) before
> > > > > create_validate_stream_for_sink()
> > > > > in amdgpu_dm_connector_mode_valid()
> > > > > 
> > > > > or
> > > > > 
> > > > > if I comment out the decide_crtc_timing_for_drm_display_mode() in
> > > > > create_stream_for_sink()
> > > > > 
> > > > > but a better fix than these can be imagined :)
> > > 
> > > Would it help if you force recalculate_timings to be true if
> > > (drm_mode->crtc_clock == 0)
> > > 
> > 
> > Yes, it works with that one.
> > 
> > But the code would start to become quite untraceable.
> > duplicate mode in amdgpu_dm_connector_mode_valid()
> > call drm_mode_set_crtcinfo() in amdgpu_dm_connector_mode_valid()
> > duplicate mode in create_stream_for_sink()
> > overwrite ctrc in decide_crtc_timing_for_drm_display_mode()
> > if crtc_clock == 0 call drm_mode_set_crtcinfo() again in
> > create_stream_for_sink()
> 
> Well... Unfortunately I don't know AMD driver details to comment on
> this. The fix that you've posted below at least resolves a regression
> without requiring us to revert r/o drm_mode argument patches.
> 
> > 
> > saved_mode is never used after this, so I can't add the condition here
> >         if (recalculate_timing)
> >                 drm_mode_set_crtcinfo(&saved_mode, 0);
> 
> Agree
> 
> > 
> > This commit is related, I think:
> > 1101185 ("drm/amd/display: fix the ability to use lower resolution
> > modes on eDP")
> > 
> > Regards,
> > Gergo
> > 
> > ---
> > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > index bae83a129b5f..83c8c81d4015 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > @@ -6984,6 +6984,9 @@ create_stream_for_sink(struct drm_connector
> > *connector,
> >         if (recalculate_timing)
> >                 drm_mode_set_crtcinfo(&saved_mode, 0);
> > 
> > +       if (mode.crtc_clock == 0)
> > +               drm_mode_set_crtcinfo(&mode, 0);
> > +
> 
> I'd say, please post this and let AMD maintainers act upon it.
> 
> 

This patch is probably not good yet, because I think it would bring up
the problem mentioned in 1101185 ("drm/amd/display: fix the ability to
use lower resolution modes on eDP") again.

Maybe someone will come up with a better one.

Regards,
Gergo