drm/i915: stop setting cache_dirty on discrete

Should not be needed. Even with non-coherent display, we should be using
device local-memory there, and not system memory.

v2: also add a warning in i915_gem_clflush_object
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> #v1
Link: https://patchwork.freedesktop.org/patch/msgid/20211027161813.3094681-4-matthew.auld@intel.com

drivers/gpu/drm/i915/gem/i915_gem_clflush.c

@@ -74,6 +74,11 @@ bool i915_gem_clflush_object(struct drm_i915_gem_object *obj,
 
 	assert_object_held(obj);
 
+	if (IS_DGFX(i915)) {
+		WARN_ON_ONCE(obj->cache_dirty);
+		return false;
+	}
+
 	/*
 	 * Stolen memory is always coherent with the GPU as it is explicitly
 	 * marked as wc by the system, or the system is cache-coherent.
@@ -81,7 +86,7 @@ bool i915_gem_clflush_object(struct drm_i915_gem_object *obj,
 	 * anything not backed by physical memory we consider to be always
 	 * coherent and not need clflushing.
 	 */
-	if (!i915_gem_object_has_struct_page(obj) || IS_DGFX(i915)) {
+	if (!i915_gem_object_has_struct_page(obj)) {
 		obj->cache_dirty = false;
 		return false;
 	}

drivers/gpu/drm/i915/gem/i915_gem_domain.c

@@ -18,18 +18,28 @@
 
 static bool gpu_write_needs_clflush(struct drm_i915_gem_object *obj)
 {
+	struct drm_i915_private *i915 = to_i915(obj->base.dev);
+
+	if (IS_DGFX(i915))
+		return false;
+
 	return !(obj->cache_level == I915_CACHE_NONE ||
 		 obj->cache_level == I915_CACHE_WT);
 }
 
 bool i915_gem_cpu_write_needs_clflush(struct drm_i915_gem_object *obj)
 {
+	struct drm_i915_private *i915 = to_i915(obj->base.dev);
+
 	if (obj->cache_dirty)
 		return false;
 
 	if (!(obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_WRITE))
 		return true;
 
+	if (IS_DGFX(i915))
+		return false;
+
 	/* Currently in use by HW (display engine)? Keep flushed. */
 	return i915_gem_object_is_framebuffer(obj);
 }

drivers/gpu/drm/i915/gem/i915_gem_object.c

@@ -114,18 +114,21 @@ void __i915_gem_object_fini(struct drm_i915_gem_object *obj)
 void i915_gem_object_set_cache_coherency(struct drm_i915_gem_object *obj,
 					 unsigned int cache_level)
 {
+	struct drm_i915_private *i915 = to_i915(obj->base.dev);
+
 	obj->cache_level = cache_level;
 
 	if (cache_level != I915_CACHE_NONE)
 		obj->cache_coherent = (I915_BO_CACHE_COHERENT_FOR_READ |
 				       I915_BO_CACHE_COHERENT_FOR_WRITE);
-	else if (HAS_LLC(to_i915(obj->base.dev)))
+	else if (HAS_LLC(i915))
 		obj->cache_coherent = I915_BO_CACHE_COHERENT_FOR_READ;
 	else
 		obj->cache_coherent = 0;
 
 	obj->cache_dirty =
-		!(obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_WRITE);
+		!(obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_WRITE) &&
+		!IS_DGFX(i915);
 }
 
 bool i915_gem_object_can_bypass_llc(struct drm_i915_gem_object *obj)

drivers/gpu/drm/i915/gem/i915_gem_pages.c

@@ -26,6 +26,7 @@ void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
 
 	/* Make the pages coherent with the GPU (flushing any swapin). */
 	if (obj->cache_dirty) {
+		WARN_ON_ONCE(IS_DGFX(i915));
 		obj->write_domain = 0;
 		if (i915_gem_object_has_struct_page(obj))
 			drm_clflush_sg(pages);