[Intel-gfx] [PATCH] drm/i915: Do not dereference NULL crtc or fb until after checking

[Chris Wilson]

Fixes regression from
commit 4906557eb37b7fef84fad4304acef6dedf919880
Author: Rodrigo Vivi <rodrigo.vivi at gmail.com>
Date:   Thu Jul 11 18:45:05 2013 -0300

    drm/i915: Hook PSR functionality

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=67526
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Rodrigo Vivi <rodrigo.vivi at gmail.com>
Cc: Ben Widawsky <ben at bwidawsk.net>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/i915/intel_dp.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 928b42f..7e16c6e 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1514,10 +1514,10 @@ static bool intel_edp_psr_match_conditions(struct intel_dp *intel_dp)
 	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
 	struct drm_device *dev = dig_port->base.base.dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
-	struct drm_crtc *crtc = dig_port->base.base.crtc;
-	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
-	struct drm_i915_gem_object *obj = to_intel_framebuffer(crtc->fb)->obj;
-	struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
+	struct drm_crtc *crtc;
+	struct intel_crtc *intel_crtc;
+	struct drm_i915_gem_object *obj;
+	struct intel_encoder *intel_encoder;
 
 	if (!IS_HASWELL(dev)) {
 		DRM_DEBUG_KMS("PSR not supported on this platform\n");
@@ -1544,12 +1544,21 @@ static bool intel_edp_psr_match_conditions(struct intel_dp *intel_dp)
 		return false;
 	}
 
+	crtc = dig_port->base.base.crtc;
+	if (crtc == NULL) {
+		DRM_DEBUG_KMS("crtc not active for PSR\n");
+		dev_priv->no_psr_reason = PSR_CRTC_NOT_ACTIVE;
+		return false;
+	}
+
+	intel_crtc = to_intel_crtc(crtc);
 	if (!intel_crtc->active || !crtc->fb || !crtc->mode.clock) {
 		DRM_DEBUG_KMS("crtc not active for PSR\n");
 		dev_priv->no_psr_reason = PSR_CRTC_NOT_ACTIVE;
 		return false;
 	}
 
+	obj = to_intel_framebuffer(crtc->fb)->obj;
 	if (obj->tiling_mode != I915_TILING_X ||
 	    obj->fence_reg == I915_FENCE_REG_NONE) {
 		DRM_DEBUG_KMS("PSR condition failed: fb not tiled or fenced\n");
-- 
1.8.4.rc0