[PATCH] drm/sun4i: dsi: set the connector orientation from the panel node

[Romain TISSERAND <romain.tisserand@gmail.com>]

sun6i_dsi_attach() only accepts the panel once the DRM device is
registered, and returns -EPROBE_DEFER until then. By that time the
connector can no longer get a "panel orientation" property: it has to be
attached before registration. The fbdev emulation is also set up from the
hotplug event of the attach, so it gets no rotation hint either.

As a result the rotation property of a DSI panel on these SoCs is ignored:
on the PocketGo S30 (A33, 320x480 panel mounted for landscape use,
rotation = <270>) the console and the boot splash stay in portrait.

The panel is a child node of the DSI host, so read its orientation from
the device tree when binding, before the device is registered, and set it
on the connector then.

Signed-off-by: Romain TISSERAND <romain.tisserand@gmail.com>
---
Notes:
- Testing: built with W=1 for arm (multi_v7_defconfig, DRM_SUN6I_DSI=y
  and =m) and arm64 (defconfig, =m), no warnings. Tested on a PocketGo
  S30 (A33, ILI9488 DSI panel, rotation = <270>): on 6.18.54 with the same
  change (6.18 still calls the helper of_drm_get_panel_orientation()) the
  console and plymouth come up in landscape, where they were in portrait;
  on 7.3.1 with this patch the DSI connector reports "panel orientation"
  = "Left Side Up".
  Not tested on other boards; boards without a rotation property keep the
  current behaviour (no property is attached).
- Tool disclosure: this patch was prepared with Claude Opus 5.5
  (Anthropic) as a coding assistant, in an interactive session where I
  asked it to fix the console orientation on the PocketGo S30. It traced
  why the connector never got the orientation, wrote the change and the
  message. I reviewed and understand it, and tested it as described.

 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 28 ++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index d504ae5832..1eb8a4cde0 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -22,6 +22,7 @@
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_encoder.h>
 #include <drm/drm_mipi_dsi.h>
+#include <drm/drm_of.h>
 #include <drm/drm_panel.h>
 #include <drm/drm_print.h>
 #include <drm/drm_probe_helper.h>
@@ -1055,6 +1056,31 @@ static const struct regmap_config sun6i_dsi_regmap_config = {
 	.name		= "mipi-dsi",
 };
 
+/*
+ * The panel only attaches once the DRM device is registered, too late to
+ * give the connector its orientation (the property cannot be added after
+ * registration), so fbcon and the boot splash would not rotate. Read the
+ * orientation from the panel node, a child of the DSI node, at bind time.
+ */
+static void sun6i_dsi_set_panel_orientation(struct sun6i_dsi *dsi)
+{
+	enum drm_panel_orientation orientation;
+	struct device_node *np;
+
+	for_each_available_child_of_node(dsi->dev->of_node, np) {
+		if (of_node_name_eq(np, "port") || of_node_name_eq(np, "ports"))
+			continue;
+
+		if (!drm_of_get_panel_orientation(np, &orientation) &&
+		    orientation != DRM_MODE_PANEL_ORIENTATION_UNKNOWN) {
+			drm_connector_set_panel_orientation(&dsi->connector,
+							    orientation);
+			of_node_put(np);
+			return;
+		}
+	}
+}
+
 static int sun6i_dsi_bind(struct device *dev, struct device *master,
 			 void *data)
 {
@@ -1085,6 +1111,8 @@ static int sun6i_dsi_bind(struct device *dev, struct device *master,
 
 	drm_connector_attach_encoder(&dsi->connector, &dsi->encoder);
 
+	sun6i_dsi_set_panel_orientation(dsi);
+
 	dsi->drm = drm;
 
 	return 0;

base-commit: a1e63ab695ad76850ab9787b9eb6aab695dc2965
-- 
2.43.0