From 63256ec5347fb2344a42adbae732b90603c92f35 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Tue, 4 Jan 2011 18:42:07 +0000 Subject: drm/i915: Enforce write ordering through the GTT We need to ensure that writes through the GTT land before any modification to the MMIO registers and so must impose a mandatory write barrier when flushing the GTT domain. This was revealed by relaxing the write ordering by experimentally mapping the registers and the GATT as write-combining. Signed-off-by: Chris Wilson --- drivers/gpu/drm/i915/i915_gem.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) (limited to 'drivers/gpu/drm/i915/i915_gem.c') diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index c79c0b6..f9c093c 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2393,6 +2393,12 @@ i915_gem_object_flush_fence(struct drm_i915_gem_object *obj, obj->last_fenced_ring = NULL; } + /* Ensure that all CPU reads are completed before installing a fence + * and all writes before removing the fence. + */ + if (obj->base.read_domains & I915_GEM_DOMAIN_GTT) + mb(); + return 0; } @@ -2833,10 +2839,16 @@ i915_gem_object_flush_gtt_write_domain(struct drm_i915_gem_object *obj) if (obj->base.write_domain != I915_GEM_DOMAIN_GTT) return; - /* No actual flushing is required for the GTT write domain. Writes + /* No actual flushing is required for the GTT write domain. Writes * to it immediately go to main memory as far as we know, so there's * no chipset flush. It also doesn't land in render cache. + * + * However, we do have to enforce the order so that all writes through + * the GTT land before any writes to the device, such as updates to + * the GATT itself. */ + wmb(); + i915_gem_release_mmap(obj); old_write_domain = obj->base.write_domain; -- cgit v1.1