linux-kernel - Re: amdgpu_dm_connector_mode

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Message-ID: <CALT56yPd-xfd=47xRxrCk4F3jib4Ti7kg8pRXy-gVAQpbOc=pw@mail.gmail.com>
Date: Wed, 2 Apr 2025 16:36:40 +0300
From: Dmitry Baryshkov <dbaryshkov@...il.com>
To: Gergo Koteles <soyer@....hu>
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

On Wed, 2 Apr 2025 at 15:00, Gergo Koteles <soyer@....hu> wrote:
>
> to: Dmitry's new address
> cc: regressions
>
> On Wed, 2025-04-02 at 12:40 +0200, Gergo Koteles wrote:
> > Hi,
> >
> > While playing with
> > https://lore.kernel.org/all/61c3df83ab73aba0bc7a941a443cd7faf4cf7fb0.1743195250.git.soyer@irl.hu/
> >
> > I found a regression that prevented some EDID DTDs from being selected
> > in some specific cases.
> >
> > This is the first bad commit:
> > b255ce4 ("drm/amdgpu: don't change mode in
> > amdgpu_dm_connector_mode_valid()")
> >
> > I think the problem is that decide_crtc_timing_for_drm_display_mode()
> > function tries to copy the crtc information from the preferred mode,
> > but that's not filled yet if the first one is the preferred one and
> > it's not the one with the maximum refresh rate.
> >
> > amdgpu_dm_connector_mode_valid()
> > create_validate_stream_for_sink()
> > create_stream_for_sink()
> > decide_crtc_timing_for_drm_display_mode(&mode, preferred_mode, scale)
> >
> > 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)

> >
> > more information:
> > https://gitlab.freedesktop.org/drm/amd/-/issues/4085
> >
> > Regards,
> > Gergo
> >
>


-- 
With best wishes
Dmitry