drm/i915: initialize fence registers to zero when loading GEM

(cherry picked from commit b5aa8a0fc132dd512c33e7c2621d075e3b77a65e)

Unitialized fence register could leads to corrupted display. Problem
encountered on MacBooks (revision 1 and 2), directly booting from EFI
or through BIOS emulation.

(bug #21710 at freedestop.org)

Signed-off-by: Grégoire Henry <henry@pps.jussieu.fr>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 39f5c658ef5e7c9754444672e86c166cd12a0191..91ad93da91ed8c7dc6b178a316dc5bd24a8a8084 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4154,6 +4154,7 @@ i915_gem_lastclose(struct drm_device *dev)
 void
 i915_gem_load(struct drm_device *dev)
 {
+       int i;
        drm_i915_private_t *dev_priv = dev->dev_private;
 
        spin_lock_init(&dev_priv->mm.active_list_lock);
@@ -4173,6 +4174,18 @@ i915_gem_load(struct drm_device *dev)
        else
                dev_priv->num_fence_regs = 8;
 
+       /* Initialize fence registers to zero */
+       if (IS_I965G(dev)) {
+               for (i = 0; i < 16; i++)
+                       I915_WRITE64(FENCE_REG_965_0 + (i * 8), 0);
+       } else {
+               for (i = 0; i < 8; i++)
+                       I915_WRITE(FENCE_REG_830_0 + (i * 4), 0);
+               if (IS_I945G(dev) || IS_I945GM(dev) || IS_G33(dev))
+                       for (i = 0; i < 8; i++)
+                               I915_WRITE(FENCE_REG_945_8 + (i * 4), 0);
+       }
+
        i915_gem_detect_bit_6_swizzle(dev);
 }