linux-kernel - Re: [PATCH 5/6] drm/amdgpu/dm/mst: Report possible

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Message-ID: <20190927152741.GU218215@art_vandelay>
Date:   Fri, 27 Sep 2019 11:27:41 -0400
From:   Sean Paul <sean@...rly.run>
To:     Lyude Paul <lyude@...hat.com>
Cc:     amd-gfx@...ts.freedesktop.org,
        Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>,
        Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "David (ChunMing) Zhou" <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Nicholas Kazlauskas <nicholas.kazlauskas@....com>,
        David Francis <David.Francis@....com>,
        Mario Kleiner <mario.kleiner.de@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/6] drm/amdgpu/dm/mst: Report possible_crtcs
 incorrectly, for now

On Thu, Sep 26, 2019 at 06:51:07PM -0400, Lyude Paul wrote:
> This commit is seperate from the previous one to make it easier to
> revert in the future. Basically, there's multiple userspace applications
> that interpret possible_crtcs very wrong:
> 
> https://gitlab.freedesktop.org/xorg/xserver/merge_requests/277
> https://gitlab.gnome.org/GNOME/mutter/issues/759
> 
> While work is ongoing to fix these issues in userspace, we need to
> report ->possible_crtcs incorrectly for now in order to avoid
> introducing a regression in in userspace. Once these issues get fixed,
> this commit should be reverted.
> 
> Signed-off-by: Lyude Paul <lyude@...hat.com>
> Cc: Ville Syrjälä <ville.syrjala@...ux.intel.com>
> ---
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> 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 b404f1ae6df7..fe8ac801d7a5 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -4807,6 +4807,17 @@ static int amdgpu_dm_crtc_init(struct amdgpu_display_manager *dm,
>  	if (!acrtc->mst_encoder)
>  		goto fail;
>  
> +	/*
> +	 * FIXME: This is a hack to workaround the following issues:
> +	 *
> +	 * https://gitlab.gnome.org/GNOME/mutter/issues/759
> +	 * https://gitlab.freedesktop.org/xorg/xserver/merge_requests/277
> +	 *
> +	 * One these issues are closed, this should be removed

Even when these issues are closed, we'll still be introducing a regression if we
revert this change. Time for actually_possible_crtcs? :)

You also might want to briefly explain the u/s bug in case the links go sour.

> +	 */
> +	acrtc->mst_encoder->base.possible_crtcs =
> +		amdgpu_dm_get_encoder_crtc_mask(dm->adev);

Why don't we put this hack in amdgpu_dm_dp_create_fake_mst_encoder()?

Sean

> +
>  	return 0;
>  
>  fail:
> -- 
> 2.21.0
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS