[PATCH 25/27] drm/amd/display: Reject too small viewport size when validating plane

[Anson Jacob]

From: Nikola Cornij <nikola.cornij at amd.com>

[why]
Overlay won't move to a new positon if viewport size is smaller than
what can be handled. It'd either disappear or stay at the old
position. This condition is for example hit if overlay is moved too
much outside of left or top edge of the screen, but it applies to
any non-cursor plane type.

[how]
Reject this contidion at validation time. This gives the calling
level a chance to handle this gracefully and avoid inconsistent
behaivor.

Signed-off-by: Nikola Cornij <nikola.cornij at amd.com>
Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas at amd.com>
Acked-by: Anson Jacob <Anson.Jacob at amd.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 27 ++++++++++++++++++-
 .../gpu/drm/amd/display/dc/core/dc_resource.c |  4 +--
 drivers/gpu/drm/amd/display/dc/dc.h           |  1 +
 3 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index e11139ca41d4..626a8cc92d65 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -6496,8 +6496,33 @@ static int dm_plane_helper_check_state(struct drm_plane_state *state,
 	int min_scale = 0;
 	int max_scale = INT_MAX;
 
-	/* Plane enabled? Get min/max allowed scaling factors from plane caps. */
+	/* Plane enabled? Validate viewport and get scaling factors from plane caps. */
 	if (fb && state->crtc) {
+		/* Validate viewport to cover the case when only the position changes */
+		if (state->plane->type != DRM_PLANE_TYPE_CURSOR) {
+			int viewport_width = state->crtc_w;
+			int viewport_height = state->crtc_h;
+
+			if (state->crtc_x < 0)
+				viewport_width += state->crtc_x;
+			else if (state->crtc_x + state->crtc_w > new_crtc_state->mode.crtc_hdisplay)
+				viewport_width = new_crtc_state->mode.crtc_hdisplay - state->crtc_x;
+
+			if (state->crtc_y < 0)
+				viewport_height += state->crtc_y;
+			else if (state->crtc_y + state->crtc_h > new_crtc_state->mode.crtc_vdisplay)
+				viewport_height = new_crtc_state->mode.crtc_vdisplay - state->crtc_y;
+
+			/* If completely outside of screen, viewport_width and/or viewport_height will be negative,
+			 * which is still OK to satisfy the condition below, thereby also covering these cases
+			 * (when plane is completely outside of screen).
+			 * x2 for width is because of pipe-split.
+			 */
+			if (viewport_width < MIN_VIEWPORT_SIZE*2 || viewport_height < MIN_VIEWPORT_SIZE)
+				return -EINVAL;
+		}
+
+		/* Get min/max allowed scaling factors from plane caps. */
 		get_min_max_dc_plane_scaling(state->crtc->dev, fb,
 					     &min_downscale, &max_upscale);
 		/*
diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_resource.c b/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
index 68b65a090d17..0c26c2ade782 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
@@ -1153,8 +1153,8 @@ bool resource_build_scaling_params(struct pipe_ctx *pipe_ctx)
 
 	calculate_viewport(pipe_ctx);
 
-	if (pipe_ctx->plane_res.scl_data.viewport.height < 12 ||
-		pipe_ctx->plane_res.scl_data.viewport.width < 12) {
+	if (pipe_ctx->plane_res.scl_data.viewport.height < MIN_VIEWPORT_SIZE ||
+		pipe_ctx->plane_res.scl_data.viewport.width < MIN_VIEWPORT_SIZE) {
 		if (store_h_border_left) {
 			restore_border_left_from_dst(pipe_ctx,
 				store_h_border_left);
diff --git a/drivers/gpu/drm/amd/display/dc/dc.h b/drivers/gpu/drm/amd/display/dc/dc.h
index d5105924c9e0..be9adddfac96 100644
--- a/drivers/gpu/drm/amd/display/dc/dc.h
+++ b/drivers/gpu/drm/amd/display/dc/dc.h
@@ -48,6 +48,7 @@
 #define MAX_PLANES 6
 #define MAX_STREAMS 6
 #define MAX_SINKS_PER_LINK 4
+#define MIN_VIEWPORT_SIZE 12
 
 /*******************************************************************************
  * Display Core Interfaces
-- 
2.25.1