[PATCH 2/3] drm/i915: allow semaphores on SNB if DMAR is disabled

[Eugeni Dodonov <eugeni.dodonov@intel.com>]

Semaphores cause issues when DMAR is enabled. So if we are set to per-chip
default, and we are on SNB, we can enable semaphores as long as SMAR is
disabled.

Signed-off-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.c            |    2 ++
 drivers/gpu/drm/i915/i915_gem_execbuffer.c |    4 +++-
 2 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 355f1ab..565725c 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -214,6 +214,7 @@ static const struct intel_device_info intel_sandybridge_d_info = {
 	.need_gfx_hws = 1, .has_hotplug = 1,
 	.has_bsd_ring = 1,
 	.has_blt_ring = 1,
+	.enable_semaphores = 1,
 };
 
 static const struct intel_device_info intel_sandybridge_m_info = {
@@ -222,6 +223,7 @@ static const struct intel_device_info intel_sandybridge_m_info = {
 	.has_fbc = 1,
 	.has_bsd_ring = 1,
 	.has_blt_ring = 1,
+	.enable_semaphores = 1,
 };
 
 static const struct intel_device_info intel_ivybridge_d_info = {
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 094ff4c..0510735 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -32,6 +32,7 @@
 #include "i915_drv.h"
 #include "i915_trace.h"
 #include "intel_drv.h"
+#include <linux/intel-iommu.h>
 
 struct change_domains {
 	uint32_t invalidate_domains;
@@ -758,7 +759,8 @@ i915_gem_execbuffer_sync_rings(struct drm_i915_gem_object *obj,
 	if (from == NULL || to == from)
 		return 0;
 
-	if (i915_semaphores < 0 && ENABLE_SEMAPHORES(obj->base.dev))
+	/* Only enable semaphores if DMAR is disabled */
+	if (i915_semaphores < 0 && ENABLE_SEMAPHORES(obj->base.dev) && dmar_disabled)
 		enable_semaphores = 1;
 
 	/* XXX gpu semaphores are implicated in various hard hangs on SNB */
-- 
1.7.7.3