From: Maxime Ripard <mripard@kernel.org>

The new writeback controllers that can be found on the BCM2712 require
to have their horizontal and vertical size reduced by one.

Let's tie that behaviour to the compatible so we can support both the
new and old controllers.

Signed-off-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
---
 drivers/gpu/drm/vc4/vc4_drv.h |  1 +
 drivers/gpu/drm/vc4/vc4_txp.c | 14 ++++++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
index 27deb4cde02d..984fddae0048 100644
--- a/drivers/gpu/drm/vc4/vc4_drv.h
+++ b/drivers/gpu/drm/vc4/vc4_drv.h
@@ -539,6 +539,7 @@ struct vc4_crtc_data {
 struct vc4_txp_data {
 	struct vc4_crtc_data	base;
 	unsigned int has_byte_enable:1;
+	unsigned int size_minus_one:1;
 };
 
 extern const struct vc4_txp_data bcm2835_txp_data;
diff --git a/drivers/gpu/drm/vc4/vc4_txp.c b/drivers/gpu/drm/vc4/vc4_txp.c
index eaf30b2cfb5b..d2ee872e9c0b 100644
--- a/drivers/gpu/drm/vc4/vc4_txp.c
+++ b/drivers/gpu/drm/vc4/vc4_txp.c
@@ -291,6 +291,8 @@ static void vc4_txp_connector_atomic_commit(struct drm_connector *conn,
 	struct drm_gem_dma_object *gem;
 	struct drm_display_mode *mode;
 	struct drm_framebuffer *fb;
+	unsigned int hdisplay;
+	unsigned int vdisplay;
 	u32 ctrl;
 	int idx;
 	int i;
@@ -330,9 +332,17 @@ static void vc4_txp_connector_atomic_commit(struct drm_connector *conn,
 	gem = drm_fb_dma_get_gem_obj(fb, 0);
 	TXP_WRITE(TXP_DST_PTR, gem->dma_addr + fb->offsets[0]);
 	TXP_WRITE(TXP_DST_PITCH, fb->pitches[0]);
+
+	hdisplay = mode->hdisplay ?: 1;
+	vdisplay = mode->vdisplay ?: 1;
+	if (txp_data->size_minus_one) {
+		hdisplay -= 1;
+		vdisplay -= 1;
+	}
+
 	TXP_WRITE(TXP_DIM,
-		  VC4_SET_FIELD(mode->hdisplay, TXP_WIDTH) |
-		  VC4_SET_FIELD(mode->vdisplay, TXP_HEIGHT));
+		  VC4_SET_FIELD(hdisplay, TXP_WIDTH) |
+		  VC4_SET_FIELD(vdisplay, TXP_HEIGHT));
 
 	TXP_WRITE(TXP_DST_CTRL, ctrl);
 

-- 
2.34.1