drm/i915: After a reset perform a forced modeset

On more recent chipsets, restoring the display is not as simple as
writing a few registers, so force a full modeset of the current
configuration in order to retrain the display link.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 10 insertions, 7 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index e88aabdfd1d9..e58e91736f81 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -385,9 +385,6 @@ int i965_reset(struct drm_device *dev, u8 flags)
          */
         i915_gem_retire_requests(dev);
 
-        if (need_display)
-                i915_save_display(dev);
-
         /*
          * Set the domains we want to reset (GRDOM/bits 2 and 3) as
          * well as the reset bit (GR/bit 0).  Setting the GR bit
@@ -428,13 +425,19 @@ int i965_reset(struct drm_device *dev, u8 flags)
                 mutex_lock(&dev->struct_mutex);
         }
 
+        mutex_unlock(&dev->struct_mutex);
+
         /*
-         * Display needs restore too...
+         * Perform a full modeset as on later generations, e.g. Ironlake, we may
+         * need to retrain the display link and cannot just restore the register
+         * values.
          */
-        if (need_display)
-                i915_restore_display(dev);
+        if (need_display) {
+                mutex_lock(&dev->mode_config.mutex);
+                drm_helper_resume_force_mode(dev);
+                mutex_unlock(&dev->mode_config.mutex);
+        }
 
-        mutex_unlock(&dev->struct_mutex);
         return 0;
 }