Fallback to shadow for Sandybridge if we don't have access to the BLT

If we attempt to emit BLT batches without kernel support, we just end up
with EINVAL and no rendering. Prevent this, and avoid uncached
rendering, by restoring the shadow fallback paths if there is no BLT
support.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
(cherry picked from commit 18839aaec505f8bbdb0690fe694162bf09a87d5c)

Conflicts:

	src/intel_driver.c

1 files changed, 20 insertions, 0 deletions

diff --git a/src/intel_driver.c b/src/intel_driver.c
index 5a019333..eec1ae0d 100644
--- a/src/intel_driver.c
+++ b/src/intel_driver.c
@@ -1293,6 +1293,24 @@ static void I830XvInit(ScrnInfoPtr scrn)
 		   intel->colorKey);
 }
 
+static Bool can_accelerate_2d(struct intel_screen_private *intel)
+{
+	if (INTEL_INFO(intel)->gen >= 60) {
+		drm_i915_getparam_t gp;
+		int value;
+
+		/* On Sandybridge we need the BLT in order to do anything since
+		 * it so frequently used in the acceleration code paths.
+		 */
+		gp.value = &value;
+		gp.param = I915_PARAM_HAS_BLT;
+		if (drmIoctl(intel->drmSubFD, DRM_IOCTL_I915_GETPARAM, &gp))
+			return FALSE;
+	}
+
+	return TRUE;
+}
+
 /**
  * This is called before ScreenInit to do any require probing of screen
  * configuration.
@@ -2205,6 +2223,8 @@ I830ScreenInit(int scrnIndex, ScreenPtr screen, int argc, char **argv)
 
 	intel->force_fallback = FALSE;
 	intel->use_shadow = FALSE;
+	if (!can_accelerate_2d(intel))
+		intel->use_shadow = TRUE;
 
 	/* Enable tiling by default */
 	intel->tiling = TRUE;