[Intel-gfx] [PATCH] drm/i915: duct-tape locking when eDP init fails

[Daniel Vetter]

Thanks to apple gpu mux fail we detect an eDP output, but can't read
anything over dp aux. In the resulting failure path we then hit a
paranoid WARN about potential locking.

Since the WARN is pretty useful for normal operation just paper over
it in the failure case by grabbing the demanded (but for init/teardown
not really required) lock.

I've checked our driver unload code and we already don't hold the kms
lock when calling drm_mode_config_cleanup. So this won't lead to a new
deadlock when reloading i915.ko.

v2: Make it compile.

Reported-by: Dave Airlie <airlied at gmail.com>
Cc: Dave Airlie <airlied at gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/i915/intel_dp.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index d7d4afe..8fc93f9 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -2559,12 +2559,15 @@ void intel_dp_encoder_destroy(struct drm_encoder *encoder)
 {
 	struct intel_digital_port *intel_dig_port = enc_to_dig_port(encoder);
 	struct intel_dp *intel_dp = &intel_dig_port->dp;
+	struct drm_device *dev = intel_dp_to_dev(intel_dp);
 
 	i2c_del_adapter(&intel_dp->adapter);
 	drm_encoder_cleanup(encoder);
 	if (is_edp(intel_dp)) {
 		cancel_delayed_work_sync(&intel_dp->panel_vdd_work);
+		mutex_lock(&dev->mode_config.mutex);
 		ironlake_panel_vdd_off_sync(intel_dp);
+		mutex_unlock(&dev->mode_config.mutex);
 	}
 	kfree(intel_dig_port);
 }
-- 
1.7.10.4