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, 6 insertions, 6 deletions

diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
index a8d43ad5352c..778c887108b7 100644
--- a/drivers/gpu/drm/i915/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/intel_dp_mst.c
@@ -29,9 +29,9 @@
 #include <drm/drm_crtc_helper.h>
 #include <drm/drm_edid.h>
 
-static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
-					struct intel_crtc_state *pipe_config,
-					struct drm_connector_state *conn_state)
+static int intel_dp_mst_compute_config(struct intel_encoder *encoder,
+				       struct intel_crtc_state *pipe_config,
+				       struct drm_connector_state *conn_state)
 {
 	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
 	struct intel_dp_mst_encoder *intel_mst = enc_to_mst(&encoder->base);
@@ -48,7 +48,7 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
 					   DP_DPCD_QUIRK_CONSTANT_N);
 
 	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLSCAN)
-		return false;
+		return -EINVAL;
 
 	pipe_config->output_format = INTEL_OUTPUT_FORMAT_RGB;
 	pipe_config->has_pch_encoder = false;
@@ -85,7 +85,7 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
 		if (slots < 0) {
 			DRM_DEBUG_KMS("failed finding vcpi slots:%d\n",
 				      slots);
-			return false;
+			return slots;
 		}
 	}
 
@@ -103,7 +103,7 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
 
 	intel_ddi_compute_min_voltage_level(dev_priv, pipe_config);
 
-	return true;
+	return 0;
 }
 
 static int intel_dp_mst_atomic_check(struct drm_connector *connector,