[PATCH] drm/amd/display: Skip create new stream if crtc state doesn't change

[Kazlauskas, Nicholas]

On 1/14/19 1:41 PM, Jerry (Fangzhi) Zuo wrote:
> Need to check if crtc state is changed so that mode set is
> required before trying to create new stream.
> 
> It deals with the MST hotplug use case when plug back to the
> same connector where the failure to create new stream for the
> inactive crtc state. Simply skip the check for the old connector
> and go through the new one.
> 
> Signed-off-by: Jerry (Fangzhi) Zuo <Jerry.Zuo at amd.com>

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>

Maybe in the future we should look into cleaning up the disable/enable 
codepath into a single function that does both.

This looks fine to me for now at least.

Nicholas Kazlauskas

> ---
>   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 4 ++++
>   1 file changed, 4 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 987095ccd2c5..31ac44b56eaf 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -5611,6 +5611,9 @@ static int dm_update_crtc_state(struct amdgpu_display_manager *dm,
>   		dm_new_conn_state = to_dm_connector_state(drm_new_conn_state);
>   		dm_old_conn_state = to_dm_connector_state(drm_old_conn_state);
>   
> +		if (!drm_atomic_crtc_needs_modeset(new_crtc_state))
> +			goto skip_modeset;
> +
>   		new_stream = create_stream_for_sink(aconnector,
>   						     &new_crtc_state->mode,
>   						    dm_new_conn_state,
> @@ -5640,6 +5643,7 @@ static int dm_update_crtc_state(struct amdgpu_display_manager *dm,
>   		}
>   	}
>   
> +	/* mode_changed flag may get updated above, need to check again */
>   	if (!drm_atomic_crtc_needs_modeset(new_crtc_state))
>   		goto skip_modeset;
>   
>