From f6b64b7a3a3881cc3826a47a5a64f1859ddd78e3 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Sun, 7 Nov 2010 11:50:02 +0000
Subject: [PATCH] --- yaml --- r: 228696 b: refs/heads/master c:
 629e894173c9de589913cf649deaadec4b0579bd h: refs/heads/master v: v3

---
 [refs]                                        |  2 +-
 trunk/drivers/gpu/drm/i915/intel_ringbuffer.c | 32 ++++++++++++++-----
 2 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/[refs] b/[refs]
index 11b3b1bcdf27..0d2dbca8d3fe 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: ae69b42a10dafe61adb016e0e52ec1e8d1ba11b4
+refs/heads/master: 629e894173c9de589913cf649deaadec4b0579bd
diff --git a/trunk/drivers/gpu/drm/i915/intel_ringbuffer.c b/trunk/drivers/gpu/drm/i915/intel_ringbuffer.c
index 9033697783b9..f5d6151c953f 100644
--- a/trunk/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/trunk/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -180,14 +180,30 @@ static int init_ring_common(struct intel_ring_buffer *ring)
 	if ((I915_READ_CTL(ring) & RING_VALID) == 0 ||
 	    I915_READ_START(ring) != obj_priv->gtt_offset ||
 	    (I915_READ_HEAD(ring) & HEAD_ADDR) != 0) {
-		DRM_ERROR("%s initialization failed "
-				"ctl %08x head %08x tail %08x start %08x\n",
-				ring->name,
-				I915_READ_CTL(ring),
-				I915_READ_HEAD(ring),
-				I915_READ_TAIL(ring),
-				I915_READ_START(ring));
-		return -EIO;
+		if (IS_GEN6(ring->dev) && ring->dev->pdev->revision <= 8) {
+			/* Early revisions of Sandybridge do not like
+			 * revealing the contents of the ring buffer
+			 * registers whilst idle. Fortunately, the
+			 * auto-reporting mechanism prevents most hangs,
+			 * but this will bite us eventually...
+			 */
+			DRM_DEBUG("%s initialization failed "
+				  "ctl %08x head %08x tail %08x start %08x. Ignoring, hope for the best!\n",
+				  ring->name,
+				  I915_READ_CTL(ring),
+				  I915_READ_HEAD(ring),
+				  I915_READ_TAIL(ring),
+				  I915_READ_START(ring));
+		} else {
+			DRM_ERROR("%s initialization failed "
+				  "ctl %08x head %08x tail %08x start %08x\n",
+				  ring->name,
+				  I915_READ_CTL(ring),
+				  I915_READ_HEAD(ring),
+				  I915_READ_TAIL(ring),
+				  I915_READ_START(ring));
+			return -EIO;
+		}
 	}
 
 	if (!drm_core_check_feature(ring->dev, DRIVER_MODESET))