[PATCH 5/5] drm/i915: Fix intel_dp_mst_best_encoder()

Lyude Paul lyude at redhat.com
Fri Oct 5 21:55:45 UTC 2018

Currently, i915 appears to rely on blocking modesets on
no-longer-present MSTB ports by simply returning NULL for
->best_encoder(), which in turn causes any new atomic commits that don't
disable the CRTC to fail. This is wrong however, since we still want to
allow userspace to disable CRTCs on no-longer-present MSTB ports by
changing the DPMS state to off and this still requires that we retrieve
an encoder.

So, fix this by always returning a valid encoder regardless of the state
of the MST port.

Signed-off-by: Lyude Paul <lyude at redhat.com>
Cc: stable at vger.kernel.org

Changes since v1:
- Remove mst atomic helper, since this got replaced with a much simpler

Signed-off-by: Lyude Paul <lyude at redhat.com>
 drivers/gpu/drm/i915/intel_dp_mst.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
index 69524dc59e7a..21ae4c8e8ac1 100644
--- a/drivers/gpu/drm/i915/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/intel_dp_mst.c
@@ -403,8 +403,6 @@ static struct drm_encoder *intel_mst_atomic_best_encoder(struct drm_connector *c
 	struct intel_dp *intel_dp = intel_connector->mst_port;
 	struct intel_crtc *crtc = to_intel_crtc(state->crtc);
-	if (intel_connector->mst_port_gone)
-		return NULL;
 	return &intel_dp->mst_encoders[crtc->pipe]->base.base;

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