[PATCH v2 1/2] drm/vc4: Fix negative X/Y positioning on SAND planes

[Boris Brezillon]

Commit 3e407417b192 ("drm/vc4: Fix X/Y positioning of planes using
T_TILES modifier") fixed the problem with T_TILES format, but left
things in a non-working state for SAND formats. Address that now.

Signed-off-by: Boris Brezillon <boris.brezillon at bootlin.com>
---
Hi Eric,

So, I finally spent time debugging my SANDXXX pattern generator and
could validate that negative X/Y positioning does not work (which I
was expecting :-)). The fix turns out to be simpler than I thought
(much simpler than on T-tiles), and we now have negative X/Y
positioning working on all kind of formats.

Regards,

Boris

Changes in v2:
- New patch
---
 drivers/gpu/drm/vc4/vc4_plane.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c
index 75db62cbe468..3132f5e1d16a 100644
--- a/drivers/gpu/drm/vc4/vc4_plane.c
+++ b/drivers/gpu/drm/vc4/vc4_plane.c
@@ -595,6 +595,7 @@ static int vc4_plane_mode_set(struct drm_plane *plane,
 	case DRM_FORMAT_MOD_BROADCOM_SAND128:
 	case DRM_FORMAT_MOD_BROADCOM_SAND256: {
 		uint32_t param = fourcc_mod_broadcom_param(fb->modifier);
+		u32 tile_w, tile, x_off, pix_per_tile;
 
 		/* Column-based NV12 or RGBA.
 		 */
@@ -614,12 +615,15 @@ static int vc4_plane_mode_set(struct drm_plane *plane,
 		switch (base_format_mod) {
 		case DRM_FORMAT_MOD_BROADCOM_SAND64:
 			tiling = SCALER_CTL0_TILING_64B;
+			tile_w = 64;
 			break;
 		case DRM_FORMAT_MOD_BROADCOM_SAND128:
 			tiling = SCALER_CTL0_TILING_128B;
+			tile_w = 128;
 			break;
 		case DRM_FORMAT_MOD_BROADCOM_SAND256:
 			tiling = SCALER_CTL0_TILING_256B_OR_T;
+			tile_w = 256;
 			break;
 		default:
 			break;
@@ -630,6 +634,28 @@ static int vc4_plane_mode_set(struct drm_plane *plane,
 			return -EINVAL;
 		}
 
+		pix_per_tile = tile_w / fb->format->cpp[0];
+		tile = vc4_state->src_x / pix_per_tile;
+		x_off = vc4_state->src_x % pix_per_tile;
+
+		/* Adjust the base pointer to the first pixel to be scanned
+		 * out.
+		 */
+		for (i = 0; i < num_planes; i++) {
+			vc4_state->offsets[i] += param * tile_w * tile;
+			vc4_state->offsets[i] += (vc4_state->src_y /
+						  (i ? v_subsample : 1)) *
+						 tile_w;
+		}
+
+		/*
+		 * SCALER_PITCH0_SINK_PIX does not seem to work for SAND
+		 * formats. Specify a negative START_X instead, even if it's
+		 * less efficient.
+		 */
+		if (x_off)
+			vc4_state->crtc_x = -x_off;
+
 		pitch0 = VC4_SET_FIELD(param, SCALER_TILE_HEIGHT);
 		break;
 	}
@@ -655,7 +681,8 @@ static int vc4_plane_mode_set(struct drm_plane *plane,
 	vc4_state->pos0_offset = vc4_state->dlist_count;
 	vc4_dlist_write(vc4_state,
 			VC4_SET_FIELD(state->alpha >> 8, SCALER_POS0_FIXED_ALPHA) |
-			VC4_SET_FIELD(vc4_state->crtc_x, SCALER_POS0_START_X) |
+			VC4_SET_FIELD(vc4_state->crtc_x & SCALER_POS0_START_X_MASK,
+				      SCALER_POS0_START_X) |
 			VC4_SET_FIELD(vc4_state->crtc_y, SCALER_POS0_START_Y));
 
 	/* Position Word 1: Scaled Image Dimensions. */
-- 
2.17.1