[PATCH v2 2/7] drm/tilcdc: Add blue-and-red-crossed devicetree property

[Jyri Sarha]

Add "blue-and-red-crossed"-device tree property and update devicetree
binding document. The red and blue components are reversed between 24
and 16 bit modes on am335x LCDC output pins. To get 24 RGB format the
red and blue wires has to be crossed and this in turn causes 16 colors
output to be in BGR format. With straight wiring the 16 color is RGB
and 24 bit is BGR. The new property describes whether the red and blue
wires are crossed or not. If the wires are crossed this boolean property
should be present in the relevant devicetree node.

The am335x-evm and am335x-evm have the blue and red wires crossed for
24 bit RGB mode and after this patch their LCDC nodes should have this
property to get correct colors in the display.

For more details see section 3.1.1 in AM335x Silicon Errata:
http://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=sprz360

Signed-off-by: Jyri Sarha <jsarha at ti.com>
---
 .../devicetree/bindings/display/tilcdc/tilcdc.txt  | 12 +++++++++++
 drivers/gpu/drm/tilcdc/tilcdc_drv.c                | 24 ++++++++++++++++++++++
 drivers/gpu/drm/tilcdc/tilcdc_drv.h                |  4 ++++
 drivers/gpu/drm/tilcdc/tilcdc_plane.c              |  9 +++-----
 4 files changed, 43 insertions(+), 6 deletions(-)

diff --git a/Documentation/devicetree/bindings/display/tilcdc/tilcdc.txt b/Documentation/devicetree/bindings/display/tilcdc/tilcdc.txt
index 6efa4c5..48a660a 100644
--- a/Documentation/devicetree/bindings/display/tilcdc/tilcdc.txt
+++ b/Documentation/devicetree/bindings/display/tilcdc/tilcdc.txt
@@ -17,6 +17,8 @@ Optional properties:
    the lcd controller.
  - max-pixelclock: The maximum pixel clock that can be supported
    by the lcd controller in KHz.
+ - blue-and-red-crossed: Boolean property, set this of blue and red wires
+   for LCD_DATA are crossed for 24-bit RGB support (and 16-bit BGR mode). [1]
 
 Optional nodes:
 
@@ -28,6 +30,14 @@ Optional nodes:
    Documentation/devicetree/bindings/display/tilcdc/tfp410.txt for connecting
    tfp410 DVI encoder or lcd panel to lcdc
 
+[1] There is an errata about AM335x color wiring. For 16-bit color mode
+    the wires work as they should (LCD_DATA[0:4] is for Blue[3:7]),
+    but for 24 bit color modes the wiring of blue and red components is
+    crossed and LCD_DATA[0:4] is for Red[3:7] and LCD_DATA[11:15] is
+    for Blue[3-7]. For more details see section 3.1.1 in AM335x
+    Silicon Errata:
+    http://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=sprz360
+
 Example:
 
 	fb: fb at 4830e000 {
@@ -37,6 +47,8 @@ Example:
 		interrupts = <36>;
 		ti,hwmods = "lcdc";
 
+		blue-and-red-wiring = "crossed";
+
 		port {
 			lcdc_0: endpoint at 0 {
 				remote-endpoint = <&hdmi_0>;
diff --git a/drivers/gpu/drm/tilcdc/tilcdc_drv.c b/drivers/gpu/drm/tilcdc/tilcdc_drv.c
index e45c268..bb65872 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_drv.c
+++ b/drivers/gpu/drm/tilcdc/tilcdc_drv.c
@@ -33,6 +33,16 @@
 
 static LIST_HEAD(module_list);
 
+static const u32 tilcdc_rev1_formats[] = { DRM_FORMAT_RGB565 };
+
+static const u32 tilcdc_straight_formats[] = { DRM_FORMAT_RGB565,
+					       DRM_FORMAT_BGR888,
+					       DRM_FORMAT_XBGR8888 };
+
+static const u32 tilcdc_crossed_formats[] = { DRM_FORMAT_BGR565,
+					      DRM_FORMAT_RGB888,
+					      DRM_FORMAT_XRGB8888 };
+
 void tilcdc_module_init(struct tilcdc_module *mod, const char *name,
 		const struct tilcdc_module_ops *funcs)
 {
@@ -318,6 +328,20 @@ static int tilcdc_load(struct drm_device *dev, unsigned long flags)
 
 	pm_runtime_put_sync(dev->dev);
 
+	if (priv->rev == 1) {
+		DBG("Revision 1 LCDC supports only RGB565 format");
+		priv->pixelformats = tilcdc_rev1_formats;
+		priv->num_pixelformats = ARRAY_SIZE(tilcdc_rev1_formats);
+	} else if (of_property_read_bool(node, "blue-and-red-crossed")) {
+		DBG("Configured for crossed blue and red wires");
+		priv->pixelformats = tilcdc_crossed_formats;
+		priv->num_pixelformats = ARRAY_SIZE(tilcdc_crossed_formats);
+	} else {
+		DBG("Configured for straight blue and red wires");
+		priv->pixelformats = tilcdc_straight_formats;
+		priv->num_pixelformats = ARRAY_SIZE(tilcdc_straight_formats);
+	}
+
 	ret = modeset_init(dev);
 	if (ret < 0) {
 		dev_err(dev->dev, "failed to initialize mode setting\n");
diff --git a/drivers/gpu/drm/tilcdc/tilcdc_drv.h b/drivers/gpu/drm/tilcdc/tilcdc_drv.h
index 13001df..0e19c14 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_drv.h
+++ b/drivers/gpu/drm/tilcdc/tilcdc_drv.h
@@ -65,6 +65,10 @@ struct tilcdc_drm_private {
 	 */
 	uint32_t max_width;
 
+	/* Supported pixel formats */
+	const uint32_t *pixelformats;
+	uint32_t num_pixelformats;
+
 	/* The context for pm susped/resume cycle is stored here */
 	struct drm_atomic_state *saved_state;
 
diff --git a/drivers/gpu/drm/tilcdc/tilcdc_plane.c b/drivers/gpu/drm/tilcdc/tilcdc_plane.c
index 41911e3..74c65fa 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_plane.c
+++ b/drivers/gpu/drm/tilcdc/tilcdc_plane.c
@@ -24,10 +24,6 @@
 
 #include "tilcdc_drv.h"
 
-static const u32 tilcdc_formats[] = { DRM_FORMAT_RGB565,
-				      DRM_FORMAT_RGB888,
-				      DRM_FORMAT_XRGB8888 };
-
 static struct drm_plane_funcs tilcdc_plane_funcs = {
 	.update_plane	= drm_atomic_helper_update_plane,
 	.disable_plane	= drm_atomic_helper_disable_plane,
@@ -114,12 +110,13 @@ static const struct drm_plane_helper_funcs plane_helper_funcs = {
 int tilcdc_plane_init(struct drm_device *dev,
 		      struct drm_plane *plane)
 {
+	struct tilcdc_drm_private *priv = dev->dev_private;
 	int ret;
 
 	ret = drm_plane_init(dev, plane, 1,
 			     &tilcdc_plane_funcs,
-			     tilcdc_formats,
-			     ARRAY_SIZE(tilcdc_formats),
+			     priv->pixelformats,
+			     priv->num_pixelformats,
 			     true);
 	if (ret) {
 		dev_err(dev->dev, "Failed to initialize plane: %d\n", ret);
-- 
1.9.1