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

[Hannes Schmelzer]

On 04/27/2016 01:21 AM, Martin Pietryka wrote:
> 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;
please return -1 on error;
I would also suggest to put this switch case above the first hw-access 
or doing anything on lcd,
so the controller and display leaves untouched on wrong parameters.
> +	}
> +
> +	lcdhw->raster_ctrl = raster_ctrl;
>   
>   	gd->fb_base += 0x20;	/* point fb behind palette */
>   
best regards,
Hannes