drm/i915: Do not dereference NULL crtc or fb until after checking

Fixes regression from
commit 4906557eb37b7fef84fad4304acef6dedf919880
Author: Rodrigo Vivi <rodrigo.vivi@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@chris-wilson.co.uk>
Cc: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 4a7ba5ea9ee3..d0c3f9b08387 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1545,12 +1545,21 @@ 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");