[PATCH 3/3] drm/tiny: ssd16xx: reject rotation changes without a matching mode

[LiangCheng Wang]

Portrait orientations are implemented by packing the framebuffer
column-major into the same physical RAM layout, so they need the
transposed mode that ssd16xx_connector_get_modes() reports, and a
framebuffer to match.

Setting the rotation property to 90 or 270 on its own provides neither:
the client keeps the mode and framebuffer it had while the driver switches
to portrait packing, and the result is displayed as garbage.  Nothing
reports an error, and data_size is identical either way so no size check
catches it.

Reject the combination in the CRTC atomic check, so userspace gets -EINVAL
and can re-probe and do a full modeset instead.  Rotation set through the
DT "rotation" property is unaffected, since probe() swaps the mode
dimensions before the connector is registered.

Tested on a Mayqueen PIXPAPER 4.26m (SSD1677, 800x480): rotation 90 at
runtime now fails with -EINVAL instead of corrupting the display, 180 still
applies, and DT rotation = <90> still comes up as 480x800.

Signed-off-by: LiangCheng Wang <zaq14760@xxxxxxxxx>
---
 drivers/gpu/drm/tiny/ssd16xx.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/drivers/gpu/drm/tiny/ssd16xx.c b/drivers/gpu/drm/tiny/ssd16xx.c
index d311720bbfbe0dd288dbd588be02c79b5eab3eab..1224a3d4ce2cbe70406dfa6e550fc85a2ea62682 100644
--- a/drivers/gpu/drm/tiny/ssd16xx.c
+++ b/drivers/gpu/drm/tiny/ssd16xx.c
@@ -1730,6 +1730,40 @@ static enum drm_mode_status ssd16xx_crtc_mode_valid(struct drm_crtc *crtc,
 static int ssd16xx_crtc_atomic_check(struct drm_crtc *crtc,
 				     struct drm_atomic_commit *state)
 {
+	struct ssd16xx_device *device = crtc_to_ssd16xx_device(crtc);
+	struct drm_crtc_state *new_crtc_state =
+		drm_atomic_get_new_crtc_state(state, crtc);
+	struct drm_connector_state *new_conn_state;
+	unsigned int orientation;
+	bool want_portrait, mode_is_portrait;
+
+	if (!new_crtc_state->enable)
+		return 0;
+
+	new_conn_state = drm_atomic_get_new_connector_state(state,
+							    &device->connector);
+	if (!new_conn_state)
+		return 0;
+
+	/*
+	 * Portrait packing needs the transposed mode that
+	 * ssd16xx_connector_get_modes() reports; without it the client keeps a
+	 * framebuffer that would be packed with the wrong geometry.
+	 */
+	orientation = to_ssd16xx_connector_state(new_conn_state)->orientation;
+	want_portrait = (orientation == 90 || orientation == 270);
+	mode_is_portrait = new_crtc_state->mode.hdisplay <
+			   new_crtc_state->mode.vdisplay;
+
+	if (want_portrait != mode_is_portrait) {
+		drm_dbg(&device->drm,
+			"atomic_check: %u° orientation needs a %s mode, but %ux%u is set\n",
+			orientation, want_portrait ? "portrait" : "landscape",
+			new_crtc_state->mode.hdisplay,
+			new_crtc_state->mode.vdisplay);
+		return -EINVAL;
+	}
+
 	return 0;
 }
 

-- 
2.34.1