[U-Boot] Maintain U-Boot splash until application is loaded

[Anatolij Gustschin]

Hi Otavio,

On Tue, 4 Jun 2013 23:13:43 -0300
Otavio Salvador <otavio at ossystems.com.br> wrote:
...
> I am working in a product and we'd like to keep the U-Boot splash until the
> application has been loaded so we have a graceful initialization. This
> project uses MX23 (so mxs SoC family).
> 
> I tried to check the U-Boot mailing list archive for it but I couldn't find
> anything useful. I also did look at kernel source and it seems
> CONFIG_FB_PRE_INIT_FB is available for only *one* board.
> 
> Could someone advice me how to do that?

the mxs frame buffer driver in mainline linux tree looks in platform
data structure "struct mxsfb_platform_data" for fb_phys and fb_size
fields and uses this memory range for the frame buffer (if these are
initialized by platform code). But the platform code in
arch/arm/mach-mxs/mach-mxs.c doesn't initialize them. The platform
code could be extended to check if the display controller is
initialized by the boot loader and in this case it should read out
the frame buffer base address from the display controller registers
and calculate the frame buffer size using the resolution and depth
values from the controller registers. Then this frame buffer range
could be reserved (by reserve_bootmem()) so that the kernel doesn't
use it for other purposes, and the reserved range should be passed
in mxsfb_platform_data to the frame buffer driver.

When booting, the frame buffer could be used by frame buffer console
fbcon and in this case your splash will be overwritten. To prevent
this you could pass fbcon=map:1 on the kernel command line and if
the console on frame buffer is needed later, then map the console
to the frame buffer by appropriate ioctl (see con2fbmap utility).

Thanks,

Anatolij