Commit ed75a55b authored Aug 11, 2015 by Ville Syrjälä Committed by Daniel Vetter Aug 14, 2015

drm/i915: clflush on pin_to_display after pwrite to UC bo in LLC

Currently we don't clflush on pin_to_display if the bo is already
UC/WT and is not in the CPU write domain. This causes problems with
pwrite since pwrite doesn't change the write domain, and it avoids
clflushing on UC/WT buffers on LLC platforms unless the buffer is
currently being scanned out.

Fix the problem by marking the cache dirty and adjusting
i915_gem_object_set_cache_level() to clflush when the cache is dirty
even if the cache_level doesn't change.

My last attempt [1] at fixing this via write domain frobbing was shot
down, but now with the cache_dirty flag we can do things in a nicer way.

[1] http://lists.freedesktop.org/archives/intel-gfx/2014-November/055390.html

v2: Drop the I915_CACHE_NONE/WT checks from pwrite

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=86422


Testcase: igt/kms_pwrite_crc
Testcase: igt/gem_pwrite_snooped
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

parent cf1d5883

drivers/gpu/drm/i915/i915_gem.c

+6 −3

Original line number	Diff line number	Diff line
		@@ -1005,12 +1005,14 @@ i915_gem_shmem_pwrite(struct drm_device *dev,
		if (!needs_clflush_after &&
		obj->base.write_domain != I915_GEM_DOMAIN_CPU) {
		if (i915_gem_clflush_object(obj, obj->pin_display))
		i915_gem_chipset_flush(dev);
		needs_clflush_after = true;
		}
		}

		if (needs_clflush_after)
		i915_gem_chipset_flush(dev);
		else
		obj->cache_dirty = true;

		intel_fb_obj_flush(obj, false, ORIGIN_CPU);
		return ret;
		@@ -3639,10 +3641,10 @@ int i915_gem_object_set_cache_level(struct drm_i915_gem_object *obj,
		{
		struct drm_device *dev = obj->base.dev;
		struct i915_vma vma, next;
		int ret;
		int ret = 0;

		if (obj->cache_level == cache_level)
		return 0;
		goto out;

		if (i915_gem_obj_is_pinned(obj)) {
		DRM_DEBUG("can not change the cache level of pinned objects\n");
		@@ -3687,6 +3689,7 @@ int i915_gem_object_set_cache_level(struct drm_i915_gem_object *obj,
		vma->node.color = cache_level;
		obj->cache_level = cache_level;

		out:
		if (obj->cache_dirty &&
		obj->base.write_domain != I915_GEM_DOMAIN_CPU &&
		cpu_write_needs_clflush(obj)) {