[PATCH v1 1/2] drm/mipi-dbi: honour the plane source offset when flushing

[Jonathan Frazin <frazinjonathan@gmail.com>]

mipi_dbi_fb_dirty() takes the damage rectangle from
drm_atomic_helper_damage_merged(), which is expressed in framebuffer
coordinates and already clipped to the plane's source rectangle.  It
then passed that rectangle straight to mipi_dbi_set_window_address(),
which is correct only while the source rectangle starts at (0,0) - i.e.
while the framebuffer is exactly panel-sized.

If a driver allows a framebuffer larger than the panel and the plane
selects a sub-region with a non-zero src_x/src_y, the controller was
still addressed in framebuffer coordinates, so the wrong part of the
panel was written and an out-of-range window could be programmed.

Pass the integer plane source origin down to mipi_dbi_fb_dirty() and
subtract it when programming the column/page address.  The copy into the
transfer buffer still uses the framebuffer-coordinate rectangle, so it
keeps reading the correct pixels from an oversized source.  With a
panel-sized framebuffer src_x/src_y are zero and behaviour is unchanged.

Cc: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Jonathan Frazin <frazinjonathan@gmail.com>
---
 drivers/gpu/drm/drm_mipi_dbi.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_mipi_dbi.c b/drivers/gpu/drm/drm_mipi_dbi.c
index 25cf04d02..38db45a9d 100644
--- a/drivers/gpu/drm/drm_mipi_dbi.c
+++ b/drivers/gpu/drm/drm_mipi_dbi.c
@@ -271,7 +271,8 @@ static void mipi_dbi_set_window_address(struct mipi_dbi_dev *dbidev,
 }
 
 static void mipi_dbi_fb_dirty(struct iosys_map *src, struct drm_framebuffer *fb,
-			      struct drm_rect *rect, struct drm_format_conv_state *fmtcnv_state)
+			      struct drm_rect *rect, unsigned int src_x, unsigned int src_y,
+			      struct drm_format_conv_state *fmtcnv_state)
 {
 	struct mipi_dbi_dev *dbidev = drm_to_mipi_dbi_dev(fb->dev);
 	unsigned int height = rect->y2 - rect->y1;
@@ -298,8 +299,13 @@ static void mipi_dbi_fb_dirty(struct iosys_map *src, struct drm_framebuffer *fb,
 		tr = src->vaddr; /* TODO: Use mapping abstraction properly */
 	}
 
-	mipi_dbi_set_window_address(dbidev, rect->x1, rect->x2 - 1, rect->y1,
-				    rect->y2 - 1);
+	/*
+	 * @rect is in framebuffer coordinates and has been clipped to the plane
+	 * src rectangle by the damage iterator. The panel is addressed relative
+	 * to the src origin, so subtract it here.
+	 */
+	mipi_dbi_set_window_address(dbidev, rect->x1 - src_x, rect->x2 - 1 - src_x,
+				    rect->y1 - src_y, rect->y2 - 1 - src_y);
 
 	if (fb->format->format == DRM_FORMAT_XRGB8888)
 		dst_format = drm_format_info(dbidev->pixel_format);
@@ -390,6 +396,8 @@ void drm_mipi_dbi_plane_helper_atomic_update(struct drm_plane *plane,
 	if (drm_dev_enter(plane->dev, &idx)) {
 		if (drm_atomic_helper_damage_merged(old_plane_state, plane_state, &rect))
 			mipi_dbi_fb_dirty(&shadow_plane_state->data[0], fb, &rect,
+					  plane_state->src_x >> 16,
+					  plane_state->src_y >> 16,
 					  &shadow_plane_state->fmtcnv_state);
 		drm_dev_exit(idx);
 	}
-- 
2.53.0