[Intel-gfx] [PATCH] drm/i915: enable semaphores on per-device defaults

[Eugeni Dodonov]

We should enable semaphores on IVB by default, and on SNB in cases where
dma remapping is disabled or iommu is not enabled.

v2: adapt patch according to the feedback, and put it in line with Keith's
rc6 enabling patch.

CC: Daniel Vetter <daniel.vetter at ffwll.ch>
CC: Ben Widawsky <ben at bwidawsk.net>
CC: Keith Packard <keithp at keithp.com>
CC: Jesse Barnes <jbarnes at virtuousgeek.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=42696
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=40564
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=41353
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=38862
Signed-off-by: Eugeni Dodonov <eugeni.dodonov at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.c            |    4 ++--
 drivers/gpu/drm/i915/i915_gem_execbuffer.c |   24 +++++++++++++++++++++++-
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index cc531bb..83b2be4 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -58,10 +58,10 @@ module_param_named(powersave, i915_powersave, int, 0600);
 MODULE_PARM_DESC(powersave,
 		"Enable powersavings, fbc, downclocking, etc. (default: true)");
 
-unsigned int i915_semaphores __read_mostly = 0;
+unsigned int i915_semaphores __read_mostly = -1;
 module_param_named(semaphores, i915_semaphores, int, 0600);
 MODULE_PARM_DESC(semaphores,
-		"Use semaphores for inter-ring sync (default: false)");
+		"Use semaphores for inter-ring sync (default: -1 (use per-chip defaults))");
 
 unsigned int i915_enable_rc6 __read_mostly = 0;
 module_param_named(i915_enable_rc6, i915_enable_rc6, int, 0600);
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 3693e83..c19a063 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -33,6 +33,11 @@
 #include "i915_trace.h"
 #include "intel_drv.h"
 
+#ifdef CONFIG_INTEL_IOMMU
+#include <linux/dma_remapping.h>
+#include <linux/dmar.h>
+#endif
+
 struct change_domains {
 	uint32_t invalidate_domains;
 	uint32_t flush_domains;
@@ -746,6 +751,23 @@ i915_gem_execbuffer_flush(struct drm_device *dev,
 	return 0;
 }
 
+static bool
+intel_enable_semaphores(struct drm_device *dev)
+{
+	if (i915_semaphores >= 0)
+		return i915_semaphores;
+	if (INTEL_INFO(dev)->gen >= 7)
+		return 1;
+#ifdef CONFIG_INTEL_IOMMU
+	/* On gen6, we only enable semaphores if dma remapping is disabled,
+	 * or if there is no iommu.
+	 */
+	if (INTEL_INFO(dev)->gen == 6)
+		return no_iommu || dmar_disabled;
+#endif
+	return 1;
+}
+
 static int
 i915_gem_execbuffer_sync_rings(struct drm_i915_gem_object *obj,
 			       struct intel_ring_buffer *to)
@@ -758,7 +780,7 @@ i915_gem_execbuffer_sync_rings(struct drm_i915_gem_object *obj,
 		return 0;
 
 	/* XXX gpu semaphores are implicated in various hard hangs on SNB */
-	if (INTEL_INFO(obj->base.dev)->gen < 6 || !i915_semaphores)
+	if (INTEL_INFO(obj->base.dev)->gen < 6 || !intel_enable_semaphores(obj->base.dev))
 		return i915_gem_object_wait_rendering(obj);
 
 	idx = intel_ring_sync_index(from, to);
-- 
1.7.7.4