ARM: clcd: add method for describing display capabilities

The ARM CLCD PL110 controller in TFT mode provides two output formats
based on whether the controller is in 24bpp mode or not - either 5551
or 888.  PL111 augments this with a 444 and 565 modes.

Some implementations provide an external MUX on the PL110 output to
reassign the bits to achieve 565 mode.

Provide a system of capability flags to allow the CLCD driver to work
out what is supported by each panel and board, and therefore which
display formats are permitted.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 84 insertions, 11 deletions

diff --git a/drivers/video/amba-clcd.c b/drivers/video/amba-clcd.c
index aedbb345f8a9..8bd370697533 100644
--- a/drivers/video/amba-clcd.c
+++ b/drivers/video/amba-clcd.c
@@ -120,8 +120,23 @@ static void clcdfb_enable(struct clcd_fb *fb, u32 cntl)
 static int
 clcdfb_set_bitfields(struct clcd_fb *fb, struct fb_var_screeninfo *var)
 {
+	u32 caps;
 	int ret = 0;
 
+	if (fb->panel->caps && fb->board->caps)
+		caps = fb->panel->caps & fb->board->caps;
+	else {
+		/* Old way of specifying what can be used */
+		caps = fb->panel->cntl & CNTL_BGR ?
+			CLCD_CAP_BGR : CLCD_CAP_RGB;
+		/* But mask out 444 modes as they weren't supported */
+		caps &= ~CLCD_CAP_444;
+	}
+
+	/* Only TFT panels can do RGB888/BGR888 */
+	if (!(fb->panel->cntl & CNTL_LCDTFT))
+		caps &= ~CLCD_CAP_888;
+
 	memset(&var->transp, 0, sizeof(var->transp));
 
 	var->red.msb_right = 0;
@@ -133,6 +148,13 @@ clcdfb_set_bitfields(struct clcd_fb *fb, struct fb_var_screeninfo *var)
 	case 2:
 	case 4:
 	case 8:
+		/* If we can't do 5551, reject */
+		caps &= CLCD_CAP_5551;
+		if (!caps) {
+			ret = -EINVAL;
+			break;
+		}
+
 		var->red.length		= var->bits_per_pixel;
 		var->red.offset		= 0;
 		var->green.length	= var->bits_per_pixel;
@@ -140,23 +162,61 @@ clcdfb_set_bitfields(struct clcd_fb *fb, struct fb_var_screeninfo *var)
 		var->blue.length	= var->bits_per_pixel;
 		var->blue.offset	= 0;
 		break;
+
 	case 16:
-		var->red.length = 5;
-		var->blue.length = 5;
+		/* If we can't do 444, 5551 or 565, reject */
+		if (!(caps & (CLCD_CAP_444 | CLCD_CAP_5551 | CLCD_CAP_565))) {
+			ret = -EINVAL;
+			break;
+		}
+
 		/*
-		 * Green length can be 5 or 6 depending whether
-		 * we're operating in RGB555 or RGB565 mode.
+		 * Green length can be 4, 5 or 6 depending whether
+		 * we're operating in 444, 5551 or 565 mode.
 		 */
-		if (var->green.length != 5 && var->green.length != 6)
-			var->green.length = 6;
+		if (var->green.length == 4 && caps & CLCD_CAP_444)
+			caps &= CLCD_CAP_444;
+		if (var->green.length == 5 && caps & CLCD_CAP_5551)
+			caps &= CLCD_CAP_5551;
+		else if (var->green.length == 6 && caps & CLCD_CAP_565)
+			caps &= CLCD_CAP_565;
+		else {
+			/*
+			 * PL110 officially only supports RGB555,
+			 * but may be wired up to allow RGB565.
+			 */
+			if (caps & CLCD_CAP_565) {
+				var->green.length = 6;
+				caps &= CLCD_CAP_565;
+			} else if (caps & CLCD_CAP_5551) {
+				var->green.length = 5;
+				caps &= CLCD_CAP_5551;
+			} else {
+				var->green.length = 4;
+				caps &= CLCD_CAP_444;
+			}
+		}
+
+		if (var->green.length >= 5) {
+			var->red.length = 5;
+			var->blue.length = 5;
+		} else {
+			var->red.length = 4;
+			var->blue.length = 4;
+		}
 		break;
 	case 32:
-		if (fb->panel->cntl & CNTL_LCDTFT) {
-			var->red.length		= 8;
-			var->green.length	= 8;
-			var->blue.length	= 8;
+		/* If we can't do 888, reject */
+		caps &= CLCD_CAP_888;
+		if (!caps) {
+			ret = -EINVAL;
 			break;
 		}
+
+		var->red.length = 8;
+		var->green.length = 8;
+		var->blue.length = 8;
+		break;
 	default:
 		ret = -EINVAL;
 		break;
@@ -168,7 +228,20 @@ clcdfb_set_bitfields(struct clcd_fb *fb, struct fb_var_screeninfo *var)
 	 * the bitfield length defined above.
 	 */
 	if (ret == 0 && var->bits_per_pixel >= 16) {
-		if (fb->panel->cntl & CNTL_BGR) {
+		bool bgr, rgb;
+
+		bgr = caps & CLCD_CAP_BGR && var->blue.offset == 0;
+		rgb = caps & CLCD_CAP_RGB && var->red.offset == 0;
+
+		if (!bgr && !rgb)
+			/*
+			 * The requested format was not possible, try just
+			 * our capabilities.  One of BGR or RGB must be
+			 * supported.
+			 */
+			bgr = caps & CLCD_CAP_BGR;
+
+		if (bgr) {
 			var->blue.offset = 0;
 			var->green.offset = var->blue.offset + var->blue.length;
 			var->red.offset = var->green.offset + var->green.length;