From 9b37a1cac436c3722330c637391bbd17476fcfdc Mon Sep 17 00:00:00 2001 From: Jonathan Frazin Date: Mon, 31 Aug 2026 20:35:43 -0500 Subject: [PATCH 1/3] drm/mipi-dbi: honour the plane source offset when flushing 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. Signed-off-by: Jonathan Frazin --- 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 25cf04d029f77e..38db45a9dbc35e 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); } From 3ab8aa991e50ea2b6a05c9c8a5cf579439ed2985 Mon Sep 17 00:00:00 2001 From: Jonathan Frazin Date: Mon, 31 Aug 2026 20:35:45 -0500 Subject: [PATCH 2/3] drm/tiny/ili9341: allow a framebuffer larger than the panel The driver set mode_config.max_width/max_height equal to the panel dimensions, so KMS rejected any framebuffer that was not exactly panel-sized: ili9341 spi0.0: bad framebuffer width 480, should be >= 240 && <= 240 Raise the maximums so userspace can allocate a larger framebuffer and choose the displayed region through the plane's source rectangle - a crop / pan with no scaling. The minimums, the fixed display mode and the connector are unchanged, and drm_mipi_dbi now translates the source offset when addressing the controller. The transfer buffer is sized from the display mode, and the plane check (drm_mipi_dbi_plane_helper_atomic_check) forbids scaling and repositioning, so the flushed rectangle stays bounded by the panel size regardless of the framebuffer dimensions. Signed-off-by: Jonathan Frazin --- drivers/gpu/drm/tiny/ili9341.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/tiny/ili9341.c b/drivers/gpu/drm/tiny/ili9341.c index 003381aa22ea4f..6ca66e1a46bad3 100644 --- a/drivers/gpu/drm/tiny/ili9341.c +++ b/drivers/gpu/drm/tiny/ili9341.c @@ -282,9 +282,13 @@ static int ili9341_probe(struct spi_device *spi) return ret; drm->mode_config.min_width = dbidev->mode.hdisplay; - drm->mode_config.max_width = dbidev->mode.hdisplay; + /* + * Allow a framebuffer larger than the panel so a sub-region can be + * selected via the plane src rectangle (crop / pan with no scaling). + */ + drm->mode_config.max_width = 4096; drm->mode_config.min_height = dbidev->mode.vdisplay; - drm->mode_config.max_height = dbidev->mode.vdisplay; + drm->mode_config.max_height = 4096; drm->mode_config.funcs = &ili9341_mode_config_funcs; drm->mode_config.preferred_depth = 16; drm->mode_config.helper_private = &ili9341_mode_config_helper_funcs; From ca5c9486963537074865a8d9baf05f1d17cc392a Mon Sep 17 00:00:00 2001 From: Jonathan Frazin Date: Tue, 1 Sep 2026 18:33:11 -0500 Subject: [PATCH 3/3] drm/tiny/hx8357d: allow a framebuffer larger than the panel Same change as the preceding ili9341 patch: mode_config.max_width/height were pinned to the panel dimensions, rejecting any framebuffer that was not exactly panel-sized. Raise them so a sub-region of a larger framebuffer can be displayed via the plane source rectangle, now that drm_mipi_dbi translates the source offset. The fixed mode, the minimums and the connector are unchanged; the plane check forbids scaling and repositioning and tx_buf is sized from the mode, so the flushed rectangle stays bounded by the panel. Compile-tested only; the functional testing was done on ili9341. Signed-off-by: Jonathan Frazin --- drivers/gpu/drm/tiny/hx8357d.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/tiny/hx8357d.c b/drivers/gpu/drm/tiny/hx8357d.c index f942a8d09ff229..1345cf71cf5c31 100644 --- a/drivers/gpu/drm/tiny/hx8357d.c +++ b/drivers/gpu/drm/tiny/hx8357d.c @@ -320,9 +320,13 @@ static int hx8357d_probe(struct spi_device *spi) return ret; drm->mode_config.min_width = dbidev->mode.hdisplay; - drm->mode_config.max_width = dbidev->mode.hdisplay; + /* + * Allow a framebuffer larger than the panel so a sub-region can be + * selected via the plane src rectangle (crop / pan with no scaling). + */ + drm->mode_config.max_width = 4096; drm->mode_config.min_height = dbidev->mode.vdisplay; - drm->mode_config.max_height = dbidev->mode.vdisplay; + drm->mode_config.max_height = 4096; drm->mode_config.funcs = &hx8357d_mode_config_funcs; drm->mode_config.preferred_depth = 16; drm->mode_config.helper_private = &hx8357d_mode_config_helper_funcs;