[U-Boot] [PATCH 1/2] drivers/video/am335x-fb: Add support for 16bpp format

[Martin Pietryka]

To support 16bpp we just need to change the raster_ctrl register
accordingly. Also 32bpp mode should work as well, but was not tested.
According to the TRM the uppermost byte will be ignored when
LCD_TFT_24BPP_UNPACK is set.

The switch logic is based on the Liunx kernel tilcdc driver:
drivers/gpu/drm/tilcdc/tilcdc_crtc.c: lines 407 through 419
(kernel was checked out at commit: bcc981e9ed8)

Signed-off-by: Martin Pietryka <martin.pietryka at chello.at>
---
 drivers/video/am335x-fb.c | 29 +++++++++++++++++++++++------
 1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/drivers/video/am335x-fb.c b/drivers/video/am335x-fb.c
index 0ec843f..f2b4c78 100644
--- a/drivers/video/am335x-fb.c
+++ b/drivers/video/am335x-fb.c
@@ -5,7 +5,7 @@
  * minimal framebuffer driver for TI's AM335x SoC to be compatible with
  * Wolfgang Denk's LCD-Framework (CONFIG_LCD, common/lcd.c)
  *
- * - supporting only 24bit RGB/TFT raster Mode (not using palette)
+ * - supporting 16/24/32bit RGB/TFT raster Mode (not using palette)
  * - sets up LCD controller as in 'am335x_lcdpanel' struct given
  * - starts output DMA from gd->fb_base buffer
  *
@@ -106,6 +106,8 @@ int lcd_get_size(int *line_length)
 
 int am335xfb_init(struct am335x_lcdpanel *panel)
 {
+	u32 raster_ctrl = 0;
+
 	if (0 == gd->fb_base) {
 		printf("ERROR: no valid fb_base stored in GLOBAL_DATA_PTR!\n");
 		return -1;
@@ -157,11 +159,26 @@ int am335xfb_init(struct am335x_lcdpanel *panel)
 				LCD_HBPMSB(panel->hbp) |
 				LCD_HFPMSB(panel->hfp) |
 				0x0000FF00;	/* clk cycles for ac-bias */
-	lcdhw->raster_ctrl =	LCD_TFT_24BPP_MODE |
-				LCD_TFT_24BPP_UNPACK |
-				LCD_PALMODE_RAWDATA |
-				LCD_TFT_MODE |
-				LCD_RASTER_ENABLE;
+
+	raster_ctrl =	LCD_PALMODE_RAWDATA |
+			LCD_TFT_MODE |
+			LCD_RASTER_ENABLE;
+
+	switch (panel->bpp) {
+	case 16:
+		break;
+	case 32:
+		raster_ctrl |= LCD_TFT_24BPP_UNPACK;
+		/* fallthrough */
+	case 24:
+		raster_ctrl |= LCD_TFT_24BPP_MODE;
+		break;
+	default:
+		error("am335x-fb: invalid bpp value: %d\n", panel->bpp);
+		return 1;
+	}
+
+	lcdhw->raster_ctrl = raster_ctrl;
 
 	gd->fb_base += 0x20;	/* point fb behind palette */
 
-- 
2.8.0