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;