drm/i915: Pass down rc in intel_encoder->compute_config()

Something that I completely missed when implementing the new MST VCPI
atomic helpers is that with those helpers, there's technically a chance
of us having to grab additional modeset locks in ->compute_config() and
furthermore, that means we have the potential to hit a normal modeset
deadlock. However, because ->compute_config() only returns a bool this
means we can't return -EDEADLK when we need to drop locks and try again
which means we end up just failing the atomic check permanently. Whoops.

So, fix this by modifying ->compute_config() to pass down an actual
error code instead of a bool so that the atomic check can be restarted
on modeset deadlocks.

Thanks to Ville Syrjälä for pointing this out!

Changes since v1:
* Add some newlines
* Return only -EINVAL from hsw_crt_compute_config()
* Propogate return code from intel_dp_compute_dsc_params()
* Change all of the intel_dp_compute_link_config*() variants
* Don't miss if (hdmi_port_clock_valid()) branch in
  intel_hdmi_compute_config()

[Cherry-picked from drm-misc-next to drm-intel-next-queued to fix
 linux-next & drm-tip conflict, while waiting for proper propagation of
 the DP MST series that this commit fixes. In hindsight, a topic branch
 might have been a better approach for it.]

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Fixes: eceae1472467 ("drm/dp_mst: Start tracking per-port VCPI allocations")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109320
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190115200800.3121-1-lyude@redhat.com
(cherry picked from commit 96550555a78ca3c9fda4b358549a5622810fe32c)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Daniel Vetter <daniel@ffwll.ch>

1 files changed, 7 insertions, 4 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index ce1cdd2c0c3d..c6b3b69aaeac 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -11553,10 +11553,13 @@ encoder_retry:
 			continue;
 
 		encoder = to_intel_encoder(connector_state->best_encoder);
-
-		if (!(encoder->compute_config(encoder, pipe_config, connector_state))) {
-			DRM_DEBUG_KMS("Encoder config failure\n");
-			return -EINVAL;
+		ret = encoder->compute_config(encoder, pipe_config,
+					      connector_state);
+		if (ret < 0) {
+			if (ret != -EDEADLK)
+				DRM_DEBUG_KMS("Encoder config failure: %d\n",
+					      ret);
+			return ret;
 		}
 	}