diff options
authorLinus Torvalds <torvalds@linux-foundation.org>2015-07-29 22:18:16 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-08-02 11:02:16 -0700
commit27667f4744fc5a0f3e50910e78740bac5670d18b (patch)
parentd4edea40389d6646c760aa166103caa1f32298ed (diff)
i915: temporary fix for DP MST docking station NULL pointer dereference
Ted Ts'o reports that his Lenovo T540p ThinkPad crashes at boot if attached to the docking station. This is a regression that he was able to bisect to commit 8c7b5ccb7298: "drm/i915: Use atomic helpers for computing changed flags:" The reason seems to be the new call to drm_atomic_helper_check_modeset() added to intel_modeset_compute_config(), which in turn calls update_connector_routing(), and somehow ends up picking a NULL crtc for the connector state, causing the subsequent drm_crtc_index() to OOPS. Daniel Vetter says that the fundamental issue seems to be confusion in the encoder selection, and this isn't the right fix, but while he chases down the proper fix, this at least avoids the NULL pointer dereference and makes Ted's docking station work again. Reported-bisected-and-tested-by: Theodore Ts'o <tytso@mit.edu> Cc: Daniel Vetter <daniel.vetter@intel.com> Cc: Mani Nikula <jani.nikula@linux.intel.com> Cc: Dave Airlie <airlied@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 files changed, 5 insertions, 3 deletions
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 5b59d5ad7d1c..aac212297b49 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -230,10 +230,12 @@ update_connector_routing(struct drm_atomic_state *state, int conn_idx)
connector_state->best_encoder = new_encoder;
- idx = drm_crtc_index(connector_state->crtc);
+ if (connector_state->crtc) {
+ idx = drm_crtc_index(connector_state->crtc);
- crtc_state = state->crtc_states[idx];
- crtc_state->mode_changed = true;
+ crtc_state = state->crtc_states[idx];
+ crtc_state->mode_changed = true;
+ }
DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] using [ENCODER:%d:%s] on [CRTC:%d]\n",