[PATCH AUTOSEL 5.15 08/41] drm/vc4: plane: Prevent async update if we don't have a dlist

[Sasha Levin <sashal@kernel.org>]

From: Maxime Ripard <maxime@cerno.tech>

[ Upstream commit cb468c7d84d174ab9cd638be9f5b3f1ba2b311a0 ]

The vc4 planes are setup in hardware by creating a hardware descriptor
in a dedicated RAM. As part of the process to setup a plane in KMS, we
thus need to allocate some part of that dedicated RAM to store our
descriptor there.

The async update path will just reuse the descriptor already allocated
for that plane and will modify it directly in RAM to match whatever has
been asked for.

In order to do that, it will compare the descriptor for the old plane
state and the new plane state, will make sure they fit in the same size,
and check that only the position or buffer address have changed.

Reviewed-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220610115149.964394-2-maxime@cerno.tech
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/vc4/vc4_plane.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c
index 19161b6ab27f..c085c750f1e9 100644
--- a/drivers/gpu/drm/vc4/vc4_plane.c
+++ b/drivers/gpu/drm/vc4/vc4_plane.c
@@ -1219,6 +1219,10 @@ static int vc4_plane_atomic_async_check(struct drm_plane *plane,
 
 	old_vc4_state = to_vc4_plane_state(plane->state);
 	new_vc4_state = to_vc4_plane_state(new_plane_state);
+
+	if (!new_vc4_state->hw_dlist)
+		return -EINVAL;
+
 	if (old_vc4_state->dlist_count != new_vc4_state->dlist_count ||
 	    old_vc4_state->pos0_offset != new_vc4_state->pos0_offset ||
 	    old_vc4_state->pos2_offset != new_vc4_state->pos2_offset ||
-- 
2.35.1