drm/i915: Avoid moving from CPU domain during pwrite

We can avoid an early clflush when pwriting if we use the current CPU
write domain rather than moving the object to the GTT domain for the
purposes of the pwrite. This has the advantage of not flushing the
presumably hot data that we want to upload into the bo, and of ascribing
the clflush to the execution when profiling.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Eric Anholt <eric@anholt.net>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 42866c01540dc5e2bae4cec6d7dae85520c1c2fd..4590c78f428393e115c0085a5acd372a1dbfd2df 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -971,7 +971,8 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
        if (obj_priv->phys_obj)
                ret = i915_gem_phys_pwrite(dev, obj, args, file_priv);
        else if (obj_priv->tiling_mode == I915_TILING_NONE &&
-                dev->gtt_total != 0) {
+                dev->gtt_total != 0 &&
+                obj->write_domain != I915_GEM_DOMAIN_CPU) {
                ret = i915_gem_gtt_pwrite_fast(dev, obj, args, file_priv);
                if (ret == -EFAULT) {
                        ret = i915_gem_gtt_pwrite_slow(dev, obj, args,