sandbox: Support changing the LCD colour depth

Add a new device-tree property to control the colour depth. At present we
support 16bpp and 32bpp.

While we are here, update the code to use livetree.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Anatolij Gustschin <agust@denx.de>

arch/sandbox/dts/sandbox.dtsi

@@ -83,6 +83,7 @@
 		compatible = "sandbox,lcd-sdl";
 		xres = <1366>;
 		yres = <768>;
+		log2-depth = <5>;
 	};
 
 	leds {

doc/device-tree-bindings/video/sandbox-fb.txt

@@ -2,7 +2,10 @@ Sandbox LCD
 ===========
 
 This uses the displaymode.txt binding except that only xres and yres are
-required properties.
+required properties. Also an additional optional property is defined:
+
+log2-depth: Log base 2 of the U-Boot display buffer depth (4=16bpp, 5=32bpp).
+	If not provided, a value of 4 is used.
 
 Example:
 
@@ -10,4 +13,5 @@ Example:
 		compatible = "sandbox,lcd-sdl";
 		xres = <800>;
 		yres = <600>;
+		log2-depth = <5>;
 	};

drivers/video/sandbox_sdl.c

@@ -47,13 +47,11 @@ static int sandbox_sdl_bind(struct udevice *dev)
 {
 	struct video_uc_platdata *uc_plat = dev_get_uclass_platdata(dev);
 	struct sandbox_sdl_plat *plat = dev_get_platdata(dev);
-	const void *blob = gd->fdt_blob;
-	int node = dev_of_offset(dev);
 	int ret = 0;
 
-	plat->xres = fdtdec_get_int(blob, node, "xres", LCD_MAX_WIDTH);
-	plat->yres = fdtdec_get_int(blob, node, "yres", LCD_MAX_HEIGHT);
-	plat->bpix = VIDEO_BPP16;
+	plat->xres = dev_read_u32_default(dev, "xres", LCD_MAX_WIDTH);
+	plat->yres = dev_read_u32_default(dev, "yres", LCD_MAX_HEIGHT);
+	plat->bpix = dev_read_u32_default(dev, "log2-depth", VIDEO_BPP16);
 	uc_plat->size = plat->xres * plat->yres * (1 << plat->bpix) / 8;
 	debug("%s: Frame buffer size %x\n", __func__, uc_plat->size);