[PATCH v3 4/4] drm/panel: simple: add bus-format support for panel-dpi

[Max Krummenacher <max.oss.09@gmail.com>]

From: Max Krummenacher <max.krummenacher@toradex.com>

Evaluate the device tree bus-format property to set bus_format for
a 'panel-dpi' panel. Additionally infer the bpc value from the
given bus-format.

Valid values for bus-format are found in:
<include/dt-bindings/display/dt-media-bus-format.h>

This completes the addition of panel-dpi to completely specify
a panel-simple panel from the device tree.

Signed-off-by: Max Krummenacher <max.krummenacher@toradex.com>

---

Changes in v3:
- Moved the bus-format property under the port/endpoint node as
  suggested by Rob Herring

Changes in v2:
- Fix errors found by dt_binding_check

 drivers/gpu/drm/panel/panel-simple.c | 49 ++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index 4a2e580a2f7b..f1a457f1069e 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -21,9 +21,11 @@
  * DEALINGS IN THE SOFTWARE.
  */
 
+#include <dt-bindings/display/dt-media-bus-format.h>
 #include <linux/delay.h>
 #include <linux/gpio/consumer.h>
 #include <linux/module.h>
+#include <linux/of_graph.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
@@ -449,10 +451,12 @@ static int panel_dpi_probe(struct device *dev,
 			   struct panel_simple *panel)
 {
 	struct display_timing *timing;
+	struct device_node *endpoint;
 	const struct device_node *np;
 	struct panel_desc *desc;
 	unsigned int bus_flags;
 	struct videomode vm;
+	u32 bus_format;
 	int ret;
 
 	np = dev->of_node;
@@ -477,6 +481,51 @@ static int panel_dpi_probe(struct device *dev,
 	of_property_read_u32(np, "width-mm", &desc->size.width);
 	of_property_read_u32(np, "height-mm", &desc->size.height);
 
+	endpoint = of_graph_get_endpoint_by_regs(np, -1, -1);
+	if (endpoint &&
+	    !of_property_read_u32(endpoint, "bus-format", &bus_format)) {
+		/* infer bpc from bus-format */
+		switch (bus_format) {
+		case DT_MEDIA_BUS_FMT_RGB565_1X16:
+			desc->bus_format = MEDIA_BUS_FMT_RGB565_1X16;
+			desc->bpc = 6;
+			break;
+		case DT_MEDIA_BUS_FMT_RGB666_1X18:
+			desc->bus_format = MEDIA_BUS_FMT_RGB666_1X18;
+			desc->bpc = 6;
+			break;
+		case DT_MEDIA_BUS_FMT_RGB666_1X24_CPADHI:
+			desc->bus_format = MEDIA_BUS_FMT_RGB666_1X24_CPADHI;
+			desc->bpc = 6;
+			break;
+		case DT_MEDIA_BUS_FMT_BGR888_1X24:
+			desc->bus_format = MEDIA_BUS_FMT_BGR888_1X24;
+			desc->bpc = 8;
+			break;
+		case DT_MEDIA_BUS_FMT_GBR888_1X24:
+			desc->bus_format = MEDIA_BUS_FMT_GBR888_1X24;
+			desc->bpc = 8;
+			break;
+		case DT_MEDIA_BUS_FMT_RBG888_1X24:
+			desc->bus_format = MEDIA_BUS_FMT_RBG888_1X24;
+			desc->bpc = 8;
+			break;
+		case DT_MEDIA_BUS_FMT_RGB888_1X24:
+			desc->bus_format = MEDIA_BUS_FMT_RGB888_1X24;
+			desc->bpc = 8;
+			break;
+		case DT_MEDIA_BUS_FMT_RGB888_1X32_PADHI:
+			desc->bus_format = MEDIA_BUS_FMT_RGB888_1X32_PADHI;
+			desc->bpc = 8;
+			break;
+		default:
+			dev_err(dev, "%pOF: unknown bus-format property\n", np);
+			return -EINVAL;
+		}
+	}
+
+	of_node_put(endpoint);
+
 	/* Extract bus_flags from display_timing */
 	bus_flags = 0;
 	vm.flags = timing->flags;
-- 
2.20.1