drm/i915: Support Async Flip on Linear buffers

Starting from Gen12 Async Flip is supported on linear buffers.
This patch enables support for async on linear buffer.

UseCase: In Hybrid graphics, for hardware unsupported pixel formats it
will be converted to linear memory and then composed.

v2: Added use case
v3: Added FIXME for ICL indicating the restrictions

Signed-off-by: Arun R Murthy <arun.r.murthy@intel.com>
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Signed-off-by: Animesh Manna <animesh.manna@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220906041806.4095575-1-arun.r.murthy@intel.com

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

@@ -5995,6 +5995,20 @@ static int intel_async_flip_check_hw(struct intel_atomic_state *state, struct in
 		 * this selectively if required.
 		 */
 		switch (new_plane_state->hw.fb->modifier) {
+		case DRM_FORMAT_MOD_LINEAR:
+			/*
+			 * FIXME: Async on Linear buffer is supported on ICL as
+			 * but with additional alignment and fbc restrictions
+			 * need to be taken care of. These aren't applicable for
+			 * gen12+.
+			 */
+			if (DISPLAY_VER(i915) < 12) {
+				drm_dbg_kms(&i915->drm,
+					    "[PLANE:%d:%s] Modifier does not support async flips\n",
+					    plane->base.base.id, plane->base.name);
+				return -EINVAL;
+			}
+
 		case I915_FORMAT_MOD_X_TILED:
 		case I915_FORMAT_MOD_Y_TILED:
 		case I915_FORMAT_MOD_Yf_TILED: