lcd: add functions to set up simplefb device tree

simple-framebuffer is a new device tree binding that describes a pre-
configured frame-buffer memory region and its format. The Linux kernel
contains a driver that supports this binding. Implement functions to
create a DT node (or fill in an existing node) with parameters that
describe the framebuffer format that U-Boot is using.

This will be immediately used by the Raspberry Pi board in U-Boot, and
likely will be used by the Samsung ARM ChromeBook support soon too. It
could well be used by many other boards (e.g. Tegra boards with built-in
LCD panels, which aren't yet supported by the Linux kernel).

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Simon Glass <sjg@chromium.org>

common/lcd.c

@@ -57,6 +57,10 @@
 #include <atmel_lcdc.h>
 #endif
 
+#if defined(CONFIG_LCD_DT_SIMPLEFB)
+#include <libfdt.h>
+#endif
+
 /************************************************************************/
 /* ** FONT DATA								*/
 /************************************************************************/
@@ -1182,3 +1186,86 @@ int lcd_get_screen_columns(void)
 {
 	return CONSOLE_COLS;
 }
+
+#if defined(CONFIG_LCD_DT_SIMPLEFB)
+static int lcd_dt_simplefb_configure_node(void *blob, int off)
+{
+	u32 stride;
+	fdt32_t cells[2];
+	int ret;
+	const char format[] =
+#if LCD_BPP == LCD_COLOR16
+		"r5g6b5";
+#else
+		"";
+#endif
+
+	if (!format[0])
+		return -1;
+
+	stride = panel_info.vl_col * 2;
+
+	cells[0] = cpu_to_fdt32(gd->fb_base);
+	cells[1] = cpu_to_fdt32(stride * panel_info.vl_row);
+	ret = fdt_setprop(blob, off, "reg", cells, sizeof(cells[0]) * 2);
+	if (ret < 0)
+		return -1;
+
+	cells[0] = cpu_to_fdt32(panel_info.vl_col);
+	ret = fdt_setprop(blob, off, "width", cells, sizeof(cells[0]));
+	if (ret < 0)
+		return -1;
+
+	cells[0] = cpu_to_fdt32(panel_info.vl_row);
+	ret = fdt_setprop(blob, off, "height", cells, sizeof(cells[0]));
+	if (ret < 0)
+		return -1;
+
+	cells[0] = cpu_to_fdt32(stride);
+	ret = fdt_setprop(blob, off, "stride", cells, sizeof(cells[0]));
+	if (ret < 0)
+		return -1;
+
+	ret = fdt_setprop(blob, off, "format", format, strlen(format) + 1);
+	if (ret < 0)
+		return -1;
+
+	ret = fdt_delprop(blob, off, "status");
+	if (ret < 0)
+		return -1;
+
+	return 0;
+}
+
+int lcd_dt_simplefb_add_node(void *blob)
+{
+	const char compat[] = "simple-framebuffer";
+	const char disabled[] = "disabled";
+	int off, ret;
+
+	off = fdt_add_subnode(blob, 0, "framebuffer");
+	if (off < 0)
+		return -1;
+
+	ret = fdt_setprop(blob, off, "status", disabled, sizeof(disabled));
+	if (ret < 0)
+		return -1;
+
+	ret = fdt_setprop(blob, off, "compatible", compat, sizeof(compat));
+	if (ret < 0)
+		return -1;
+
+	return lcd_dt_simplefb_configure_node(blob, off);
+}
+
+int lcd_dt_simplefb_enable_existing_node(void *blob)
+{
+	int off;
+
+	off = fdt_node_offset_by_compatible(blob, -1, "simple-framebuffer");
+	if (off < 0)
+		return -1;
+
+	return lcd_dt_simplefb_configure_node(blob, off);
+}
+#endif

doc/device-tree-bindings/video/simple-framebuffer.txt

@@ -0,0 +1,25 @@
+Simple Framebuffer
+
+A simple frame-buffer describes a raw memory region that may be rendered to,
+with the assumption that the display hardware has already been set up to scan
+out from that buffer.
+
+Required properties:
+- compatible: "simple-framebuffer"
+- reg: Should contain the location and size of the framebuffer memory.
+- width: The width of the framebuffer in pixels.
+- height: The height of the framebuffer in pixels.
+- stride: The number of bytes in each line of the framebuffer.
+- format: The format of the framebuffer surface. Valid values are:
+  - r5g6b5 (16-bit pixels, d[15:11]=r, d[10:5]=g, d[4:0]=b).
+
+Example:
+
+	framebuffer {
+		compatible = "simple-framebuffer";
+		reg = <0x1d385000 (1600 * 1200 * 2)>;
+		width = <1600>;
+		height = <1200>;
+		stride = <(1600 * 2)>;
+		format = "r5g6b5";
+	};

include/lcd.h

@@ -324,6 +324,9 @@ void lcd_show_board_info(void);
 /* Return the size of the LCD frame buffer, and the line length */
 int lcd_get_size(int *line_length);
 
+int lcd_dt_simplefb_add_node(void *blob);
+int lcd_dt_simplefb_enable_existing_node(void *blob);
+
 /************************************************************************/
 /* ** BITMAP DISPLAY SUPPORT						*/
 /************************************************************************/