[Intel-gfx] [PATCH 7/9] drm/i915: enable rc6 on ILK again^5

[Chris Wilson]

From: Ben Widawsky <ben at bwidawsk.net>

With the conversion to use the existing, well tested HW context code for
the ILK RC6 render context, let's once again try to enable RC6 by
default on ILK.

This is basically a revert of a revert and reapply of an existing patch.
RC6 has been enabled, and reverted several times on Ironlake. The most
recent:

commit 6567d748c4e94e3481e523803ec07ebd825c80d6
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Sat Nov 10 10:00:06 2012 +0000
    Revert "drm/i915: enable rc6 on ilk again"

Also, as noted here:

commit cd7988eea561a70a4f98e431c1395f913672d626
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Date:   Sun Aug 26 20:33:18 2012 +0200
    drm/i915: disable rc6 on ilk when vt-d is enabled

Do not try to turn on for VT-d case.

v2: Updated commit message (Daniel)
Disable with VT-d (Daniel)

Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
Tested-by: Chris Wilson <chris at chris-wilson.co.uk> # X still works!
---
 drivers/gpu/drm/i915/intel_pm.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 2dc8f3c..20ddaf7 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3425,9 +3425,11 @@ int intel_enable_rc6(const struct drm_device *dev)
 	if (i915_enable_rc6 >= 0)
 		return i915_enable_rc6;
 
-	/* Disable RC6 on Ironlake */
-	if (INTEL_INFO(dev)->gen == 5)
+#ifdef CONFIG_INTEL_IOMMU
+	/* Ironlake + RC6 + VT-d empirically blows up */
+	if (IS_GEN5(dev) && intel_iommu_gfx_mapped)
 		return 0;
+#endif
 
 	if (IS_HASWELL(dev)) {
 		DRM_DEBUG_DRIVER("Haswell: only RC6 available\n");
-- 
1.7.9.5