[Intel-gfx] [RFC 2/2] drm/i915: Moved the cache flush outside the 'struct_mutex' lock

[akash.goel at intel.com]

From: Akash Goel <akash.goel at intel.com>

Moved the cache flush of the preallocated shmem pages outside
the span of 'struct_mutex' lock. This shall not lead to any
redundancy as the cache flush of the newly allocated pages
will be done anyways when same buffer is submitted to GPU or
when the domain of the object is changed from CPU to GTT
in Gem page fault handler.

Signed-off-by: Akash Goel <akash.goel at intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index b19ccb8..7ab2635 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1936,8 +1936,11 @@ i915_gem_object_shmem_preallocate(struct drm_i915_gem_object *obj)
 		if (IS_ERR(page)) {
 			DRM_DEBUG_DRIVER("Failure for obj(%p), size(%x) at page(%d)\n",
 						obj, obj->base.size, i);
-			break;
+			return;
 		}
+		/* Flush the cpu cache for the page now itself */
+		drm_clflush_pages(&page, 1);
+
 		/* Decrement the extra ref count on the returned page,
 		   otherwise when 'get_pages_gtt' will be called later on
 		   in the regular path, it will also increment the ref count,
@@ -1945,6 +1948,14 @@ i915_gem_object_shmem_preallocate(struct drm_i915_gem_object *obj)
 		page_cache_release(page);
 	}
 
+	/*
+	 * Reset the CPU domain now itself, so as to avoid the cache
+	 * flush later (under 'struct_mutex' lock), as the all pages
+	 * have been cache flushed.
+	 * Hope this is safe enough to be done here.
+	 */
+	obj->base.write_domain = 0;
+
 	trace_i915_gem_obj_prealloc_end(obj);
 }
 
-- 
1.9.2