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

[Maxime Ripard <maxime.ripard@free-electrons.com>]

On Tue, Sep 01, 2015 at 10:44:58AM +0300, Siarhei Siamashka wrote:
> 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.

This serie is mostly to use fastboot to flash partition images to the
storage device. We're using it to program the flash the first time.

It's indeed significantly faster than using fel to do so (by a
guesstimate, something around 30-50%), and is more pratical in the
sense that you can later on reflash only a single partition, all of
that through USB.

However, you can also use it to simply boot a kernel, without touching
any of the device storage. The main drawback with that is that the DT
has to be appended, which prevents the use of simplefb or psci in our
case...

I tried to amend the android boot image format that fastboot sends
when doing so to add a section for the DT, but gave up when having to
deal with the image parser in u-boot.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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