On 2019-05-30 3:51 p.m., Nicholas Kazlauskas wrote:
> [Why]
> When switching from vt to desktop with EDID emulation we can receive
> an atomic commit such that we have a crtc where mode_changed = true.
>
> During the dm_update_crtc_state disable pass we remove the stream from
> the context and free it on the dm_new_crtc_state.
>
> During the enable pass we compare the new provisional stream to the
> dm_old_crtc_state->stream and determine that the stream is unchanged
> and no scaling has been changed.
>
> Following this, new_crtc_state->mode_changed is then set to false.
> The connectors haven't changed and the CRTC active state hasn't changed
> so drm_atomic_crtc_needs_modeset returns false, so we jump to
> skip_modeset and we hit:
>
> BUG_ON(dm_new_crtc_state->stream == NULL);
>
> ...since the old stream is gone from the context and the new stream is
> also still NULL.
>
> [How]
> Ensure that we still a stream to reuse before checking if we can reuse
> the old stream without a full modeset.
>
> Cc: Roman Li <Roman.Li@xxxxxxx>
> Cc: Leo Li <sunpeng.li@xxxxxxx>
> Cc: Harry Wentland <Harry.Wentland@xxxxxxx>
> Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@xxxxxxx>
Reviewed-by: Harry Wentland <harry.wentland@xxxxxxx>
Harry
> ---
> drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 12 +++++++++++-
> 1 file changed, 11 insertions(+), 1 deletion(-)
>
> 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 57359037ed7c..796f83ca7a4c 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -6248,7 +6248,17 @@ static int dm_update_crtc_state(struct amdgpu_display_manager *dm,
>
> dm_new_crtc_state->abm_level = dm_new_conn_state->abm_level;
>
> - if (dc_is_stream_unchanged(new_stream, dm_old_crtc_state->stream) &&
> + /*
> + * If we already removed the old stream from the context
> + * (and set the new stream to NULL) then we can't reuse
> + * the old stream even if the stream and scaling are unchanged.
> + * We'll hit the BUG_ON and black screen.
> + *
> + * TODO: Refactor this function to allow this check to work
> + * in all conditions.
> + */
> + if (dm_new_crtc_state->stream &&
> + dc_is_stream_unchanged(new_stream, dm_old_crtc_state->stream) &&
> dc_is_stream_scaling_unchanged(new_stream, dm_old_crtc_state->stream)) {
> new_crtc_state->mode_changed = false;
> DRM_DEBUG_DRIVER("Mode change not required, setting mode_changed to %d",
>
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