[PATCH 38/73] drm/amd/display: Fix warnings on S3 resume

[Andrey Grodzovsky]

On 11/09/2017 03:05 PM, Harry Wentland wrote:
> From: "Leo (Sunpeng) Li" <sunpeng.li at amd.com>
>
> This is a followup to the following revert:
>
> Rex Zhu    Revert "drm/amd/display: Match actual state during S3
>             resume."
>
> Three things needed to be addressed:
>
> 1. Potential memory leak on dc_state creation in atomic_check during
>     s3 resume
> 2. Warnings are now seen in dmesg during S3 resume
> 3. Since dc_state is now created in atomic_check, what the reverted
>     patch was addressing needs to be reevaluated.
>
> This change addresses the above:
>
> 1. Since the suspend procedure calls drm_atomic_state_clear, our hook
>     for releasing the dc_state is called. This frees it before
>     atomic_check creates it during resume. The leak does not occur.
>
> 2. The dc_crtc/plane_state references kept by the atomic states need to
>     be released before calling atomic_check, which warns if they are
>     non-null. This is because atomic_check is responsible for creating
>     the dc_*_states. This is a special case for S3 resume, since the
>     atomic state duplication that occurs during suspend also copies a
>     reference to the dc_*_states.
>
> 3. See 2. comments are also updated to reflect this.
>
> Change-Id: I6e342bf8134f0e5dc32888a8d894c2cd20d28296
> Signed-off-by: Leo (Sunpeng) Li <sunpeng.li at amd.com>
> Reviewed-by: Harry Wentland <Harry.Wentland at amd.com>
> ---
>   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 28 +++++++++++++++++++++++
>   1 file changed, 28 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 1c7f22146bc9..bdef1ed0dfac 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -643,6 +643,11 @@ int amdgpu_dm_display_resume(struct amdgpu_device *adev)
>   	struct drm_connector *connector;
>   	struct drm_crtc *crtc;
>   	struct drm_crtc_state *new_crtc_state;
> +	struct dm_crtc_state *dm_new_crtc_state;
> +	struct drm_plane *plane;
> +	struct drm_plane_state *new_plane_state;
> +	struct dm_plane_state *dm_new_plane_state;
> +
>   	int ret = 0;
>   	int i;
>   
> @@ -685,6 +690,29 @@ int amdgpu_dm_display_resume(struct amdgpu_device *adev)
>   	for_each_new_crtc_in_state(adev->dm.cached_state, crtc, new_crtc_state, i)
>   		new_crtc_state->active_changed = true;
>   
> +	/*
> +	 * atomic_check is expected to create the dc states. We need to release
> +	 * them here, since they were duplicated as part of the suspend
> +	 * procedure.
> +	 */
> +	for_each_new_crtc_in_state(adev->dm.cached_state, crtc, new_crtc_state, i) {
> +		dm_new_crtc_state = to_dm_crtc_state(new_crtc_state);
> +		if (dm_new_crtc_state->stream) {
> +			WARN_ON(kref_read(&dm_new_crtc_state->stream->refcount) > 1);
> +			dc_stream_release(dm_new_crtc_state->stream);
> +			dm_new_crtc_state->stream = NULL;
> +		}
> +	}
> +
> +	for_each_new_plane_in_state(adev->dm.cached_state, plane, new_plane_state, i) {
> +		dm_new_plane_state = to_dm_plane_state(new_plane_state);
> +		if (dm_new_plane_state->dc_state) {
> +			WARN_ON(kref_read(&dm_new_plane_state->dc_state->refcount) > 1);
> +			dc_plane_state_release(dm_new_plane_state->dc_state);
> +			dm_new_plane_state->dc_state = NULL;
> +		}
> +	}

I guess the warnings you are referring to are in dm_update_crtcs_state 
and dm_update_planes_state,
but I don't understand why you need to explicitly release them in 
amdgpu_dm_resume, any changed
plane/crtc states will be removed during atomic check anyway and only 
after that new one will be added,
I find strange that this doesn't work.

P.S I tried to reproduce this to see the warnings with latest 
amd-staging-drm-next (776fb8c)on CZ but the system becomes
unimpressive after going to suspend, might wanna check this on your side.

Thanks,
Andrey

> +
>   	ret = drm_atomic_helper_resume(ddev, adev->dm.cached_state);
>   
>   	drm_atomic_state_put(adev->dm.cached_state);