[U-Boot] [PATCH 10/13] sunxi: Make the fastboot buffer larger

[Siarhei Siamashka <siarhei.siamashka@gmail.com>]

On Tue, 01 Sep 2015 08:22:04 +0100
Ian Campbell <ijc@hellion.org.uk> wrote:

> On Mon, 2015-08-31 at 16:46 +0200, Maxime Ripard wrote:
> > When using fastboot and flashing a larger image such as the main partition
> > of a system, the current 32MB limit for the buffer is quite small.
> 
> (Apart from rooting/rescuing the odd phone I'm completely unfamiliar
> with fastboot, so sorry if this is all obvious).
>  
> The main partition of a system these days is measured in GB, I think.
> So why does going from 32MB to 256MB for the buffer make a useful
> difference?
> 
> Is there some enormous per-buffer overhead which needs to be amortised?
> Or is something else going on?
> 
> IOW what is the practical impact of this change?

I don't know what are Maxime's plans. But if fastboot is fast and
can load the kernel and initrd to the device over USB, then it
becomes a useful alternative to using FEL for loading kernel.

FEL is implemented by BROM, but it is not particularly fast and
the transfer speed varies for different SoC variants:
    http://linux-sunxi.org/FEL/USBBoot#SoC_support_status

Somebody might want to evaluate the use of fastboot for loading kernel
with initrd and document it at http://linux-sunxi.org/FEL/USBBoot

FEL is still needed for loading U-Boot over USB on sunxi hardware, but
U-Boot size is relatively small compared to the kernel, and especially
initrd.

-- 
Best regards,
Siarhei Siamashka