[Intel-gfx] [PATCH] drm/i915: implement SNB workaround for lazy global gtt

[Daniel Vetter]

PIPE_CONTROL on snb needs global gtt mappings in place to workaround a
hw gotcha. No other commands need such a workaround. Luckily we can
detect a PIPE_CONTROL commands easily because they have a write_domain
= I915_GEM_DOMAIN_INSTRUCTION (and nothing else has that).

v2: Binding the target of such a reloc into the global gtt actually
works instead of binding the source, which is rather pointless ...

Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/i915/i915_gem_execbuffer.c |   15 ++++++++++++++-
 1 files changed, 14 insertions(+), 1 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 962def5..1e710ae 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -278,6 +278,7 @@ i915_gem_execbuffer_relocate_entry(struct drm_i915_gem_object *obj,
 {
 	struct drm_device *dev = obj->base.dev;
 	struct drm_gem_object *target_obj;
+	struct drm_i915_gem_object *target_i915_obj;
 	uint32_t target_offset;
 	int ret = -EINVAL;
 
@@ -286,7 +287,8 @@ i915_gem_execbuffer_relocate_entry(struct drm_i915_gem_object *obj,
 	if (unlikely(target_obj == NULL))
 		return -ENOENT;
 
-	target_offset = to_intel_bo(target_obj)->gtt_offset;
+	target_i915_obj = to_intel_bo(target_obj);
+	target_offset = target_i915_obj->gtt_offset;
 
 	/* The target buffer should have appeared before us in the
 	 * exec_object list, so it should have a GTT space bound by now.
@@ -388,6 +390,17 @@ i915_gem_execbuffer_relocate_entry(struct drm_i915_gem_object *obj,
 		io_mapping_unmap_atomic(reloc_page);
 	}
 
+	/* Sandybridge PPGTT errata: We need a global gtt mapping for MI and
+	 * pipe_control writes because the gpu doesn't properly redirect them
+	 * through the ppgtt for non_secure batchbuffers. */
+	if (unlikely(IS_GEN6(dev) &&
+	    reloc->write_domain == I915_GEM_DOMAIN_INSTRUCTION &&
+	    !target_i915_obj->has_global_gtt_mapping)) {
+		i915_gem_gtt_bind_object(target_i915_obj,
+					 target_i915_obj->cache_level);
+		target_i915_obj->has_global_gtt_mapping = 1;
+	}
+
 	/* and update the user's relocation entry */
 	reloc->presumed_offset = target_offset;
 
-- 
1.7.6.4