linux-kernel - Re: amdgpu_dm_connector_mode

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Message-ID: <e323219b52cda1891a55d12ad77a2b34edc8688b.camel@irl.hu>
Date: Wed, 02 Apr 2025 16:35:05 +0200
From: Gergo Koteles <soyer@....hu>
To: Dmitry Baryshkov <dbaryshkov@...il.com>
Cc: Dmitry Baryshkov <lumag@...nel.org>, regressions@...ts.linux.dev,
  dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
  amd-gfx@...ts.freedesktop.org, Hans de Goede <hdegoede@...hat.com>,
  Alex Deucher <alexander.deucher@....com>,
  Mario Limonciello <mario.limonciello@....com>,
  Alex Hung <alex.hung@....com>,
  Harry Wentland <harry.wentland@....com>
Subject: Re: amdgpu_dm_connector_mode_valid regression

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() 

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);

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);
+
        /*
         * If scaling is enabled and refresh rate didn't change
         * we copy the vic and polarities of the old timings
--