drm/i915/display: Do not use stolen on MTL

Use smem on MTL due to a HW bug in MTL that prevents
reading from stolen memory using LMEM BAR.

v2 and v3: improve stolen skip detection(Andrzej)

Cc: Oak Zeng <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Cc: Andi Shyti <[email protected]>
Cc: Andrzej Hajda <[email protected]>
Signed-off-by: Nirmoy Das <[email protected]>
Reviewed-by: Oak Zeng <[email protected]>
Reviewed-by: Andrzej Hajda <[email protected]>
Reviewed-by: Andi Shyti <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: nirmoy

drivers/gpu/drm/i915/display/intel_fbdev.c

@@ -182,8 +182,10 @@ static int intelfb_alloc(struct drm_fb_helper *helper,
 		 * If the FB is too big, just don't use it since fbdev is not very
 		 * important and we should probably use that space with FBC or other
 		 * features.
+		 *
+		 * Also skip stolen on MTL as Wa_22018444074 mitigation.
 		 */
-		if (size * 2 < dev_priv->dsm.usable_size)
+		if (!(IS_METEORLAKE(dev_priv)) && size * 2 < dev_priv->dsm.usable_size)
 			obj = i915_gem_object_create_stolen(dev_priv, size);
 		if (IS_ERR(obj))
 			obj = i915_gem_object_create_shmem(dev_priv, size);

drivers/gpu/drm/i915/display/intel_overlay.c

@@ -1348,11 +1348,12 @@ int intel_overlay_attrs_ioctl(struct drm_device *dev, void *data,
 static int get_registers(struct intel_overlay *overlay, bool use_phys)
 {
 	struct drm_i915_private *i915 = overlay->i915;
-	struct drm_i915_gem_object *obj;
+	struct drm_i915_gem_object *obj = ERR_PTR(-ENODEV);
 	struct i915_vma *vma;
 	int err;
 
-	obj = i915_gem_object_create_stolen(i915, PAGE_SIZE);
+	if (!IS_METEORLAKE(i915)) /* Wa_22018444074 */
+		obj = i915_gem_object_create_stolen(i915, PAGE_SIZE);
 	if (IS_ERR(obj))
 		obj = i915_gem_object_create_internal(i915, PAGE_SIZE);
 	if (IS_ERR(obj))