[U-Boot] U-boot VESA driver Initialization

[Bin Meng]

On Mon, Jun 13, 2016 at 5:41 PM, vinoth eswaran <evinoth1206 at gmail.com> wrote:
> Hello Mr.Bin,
> Hello Mr.George McCollister,
>
>  I am working on an embedded project to optimize Linux boot up time. I have
> a camera application, which I need to run as fast as possible after powering
> up the board.
>
> For this currently I am analyzing how can I optimize the U-boot. As of now,
> u-boot takes around 3 to 4 seconds and most of the time is spent, around 2
> secs in initializing the VESA display.
>
> I have analyzed the sequence of VESA initialization flow and I have
> identified that realmode_call under the function bios_run_on_x86() takes
> more time -- around 1.7 Sec,
>
>     realmode_call(addr + 0x0003, num_dev, 0xffff, 0x0000, 0xffff, 0x0,
>               0x0);
>
> Do you have any idea why this is happening?
>
> I tried removing the VIDEO configuration from u-boot, though the boot up is
> fast , the i915 driver from Linux is reporting an error -- 'i915
> 0000:00:02.0: Invalid ROM contents'

Can you point out which file in the kernel source that reports this? I
cannot find such message in latest kernel source tree.

> I understand that the Linux kernel expects the underlying boot loader to
> setup some initialization which is missing in this case.
>

My understanding is that if we have native graphics driver in the
kernel, then the bootloader does not need initialize the graphics
hardware.

> Do you know any methods by which I can speed up the video driver
> initialization phase in u-boot. Please note that I don't need video support
> during u-boot phase,I am not going to use any splash images.
>

Regards,
Bin