drm/i915: Kill RMW from ILK reset code

All the other bits in the GDSR register are read-only, so we don't have
to preserve them when we perform a GPU reset.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index bfcd3bd..b542bf6 100644 (file)
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -991,22 +991,17 @@ static int i965_do_reset(struct drm_device *dev)
 static int ironlake_do_reset(struct drm_device *dev)
 {
        struct drm_i915_private *dev_priv = dev->dev_private;
-       u32 gdrst;
        int ret;
 
-       gdrst = I915_READ(MCHBAR_MIRROR_BASE + ILK_GDSR);
-       gdrst &= ~ILK_GRDOM_MASK;
        I915_WRITE(MCHBAR_MIRROR_BASE + ILK_GDSR,
-                  gdrst | ILK_GRDOM_RENDER | ILK_GRDOM_RESET_ENABLE);
+                  ILK_GRDOM_RENDER | ILK_GRDOM_RESET_ENABLE);
        ret = wait_for((I915_READ(MCHBAR_MIRROR_BASE + ILK_GDSR) &
                        ILK_GRDOM_RESET_ENABLE) == 0, 500);
        if (ret)
                return ret;
 
-       gdrst = I915_READ(MCHBAR_MIRROR_BASE + ILK_GDSR);
-       gdrst &= ~ILK_GRDOM_MASK;
        I915_WRITE(MCHBAR_MIRROR_BASE + ILK_GDSR,
-                  gdrst | ILK_GRDOM_MEDIA | ILK_GRDOM_RESET_ENABLE);
+                  ILK_GRDOM_MEDIA | ILK_GRDOM_RESET_ENABLE);
        return wait_for((I915_READ(MCHBAR_MIRROR_BASE + ILK_GDSR) &
                         ILK_GRDOM_RESET_ENABLE) == 0, 500);
 }