[U-Boot] Displaying characters on the display in u-boot

[Anatolij Gustschin]

Hi,

On Fri, 19 Apr 2013 21:29:33 +0530
Bhargav A K <bhargav.ak at sasken.com> wrote:

> Hi All,
> 
> I have enabled the following configurations.
> in my board's config header
> 
> #define CONFIG_VGA_AS_SINGLE_DEVICE
> #define CONFIG_VIDEO
> #define CONFIG_CFB_CONSOLE
> 
> video_hw_init() returns a pointer to GraphicsDevice structure.
> 
> It does the following
> -----------------------------------------------------
> omap4_GD.winSizeX = 480; //__raw_readl()
> omap4_GD.winSizeY = 800;
> omap4_GD.gdfBytesPP = 4;
> omap4_GD.gdfIndex = GDF_32BIT_X888RGB;
> 
> __raw_writel(0xA5000000, DISPC_GFX_BA0);
> omap4_GD.frameAdrs = __raw_readl(DISPC_GFX_BA0);

Why are you using 0xA5000000 address here as the frame buffer base
address? Are you sure that this is a valid memory address? Can you
see changes on the display if you write data to this address by
U-Boot "mw" command (i.e. "mw a5000000 ffffffff 100") ?
Which frame buffer base address did you use before for working
splashscreen?

> initDisplay(); // Do all other clocks, GPIOs, OMAP4 registers specific for LCD(DSI, DISPC, DSS).
> ------------------------------------------------------
> 
> board_video_init() is just a dummy call.
> 
> I did a console_assign() to redirect stderr and stdout to vga.
> All the printf's doesn't come on the serial console or the LCD.
> 
> I tried using the video_drawstring(10, 20, "hello world"),
> after resetting the stdout to serial. I see all the "printf's" on the
> serial console, but the string from video_drawstring()(hello world)
> won't come on the LCD even after syncing LCD pipelines (GO_LCD in OMAP4470).

Probably the frame buffer or display controller configuration is
wrong then. Is the display backlight enabled?

> Then I just exported the lcd_drawchars() function into my LCD code,
> tried to write characters to the LCD, nothing came onto the screen.

lcd_drawchars() will not help since you do not use the lcd driver.

Thanks,

Anatolij