[U-Boot] SPL Dfu update

[Michael Trimarchi]

Hi Tom

On Wed, Oct 30, 2013 at 2:44 PM, Tom Rini <trini at ti.com> wrote:
> On Wed, Oct 30, 2013 at 02:29:32PM +0100, Michael Trimarchi wrote:
>> Hi
>>
>> On Wed, Oct 30, 2013 at 2:28 PM, Stefano Babic <sbabic at denx.de> wrote:
>> > Hi Lukasz, hi Michael,
>> >
>> > On 30/10/2013 13:58, Lukasz Majewski wrote:
>> >
>> >> In general the presented structure is correct.
>> >>
>> >> However, I've got other concerns:
>> >>
>> >> The DFU + composite + gadget + UDC driver code is large (around 24KiB
>> >> in binary size [1] for the TRATS).
>> >>
>> >> I'm not sure if this size would be acceptable for SPL. Of course there
>> >> are some spots for code base size reduction (like optimizing and often
>> >> hardcoding code ported from linux kernel).
>> >
>> > Apart of the fact that is possible to add DFU to SPL, I am missing which
>> > is the real advantage. One goal of having split U-Boot into two images
>> > (SPL and U-Boot) is also to get a simpler and smaller image, letting the
>> > main U-Boot image doing the rest (hush shell, further drivers, and so
>> > on). We are now trying to push features that we currently have into SPL.
>> > Well, why cannot we simply run U-Boot if we need a DFU update ? Which
>> > are the real advantages for having DFU in SPL ?
>> >
>>
>> USB flashing (no serial, no display) only otg
>
> OK, but how are we getting SPL loaded?  I know of, today, some solutions
> using U-Boot + DFU for flashing/restore (and some other non-DFU flashing
> solutions) that do SPL+regular U-Boot.  I think this highlights, in
> part, once again that Scott is right and we need to think of SPL as a
> differently configured U-Boot, because the flip side here is, why should
> we load even more data before doing the payload when we know we're a
> single purpose run?

OMAP4/3 can boot over the otg, so you can send MLO and let it wait for the
second stage boot. We have already SPL USBETH in u-boot but in production
otg flashing can be very useful. Think SPL as a differently configured U-BOOT
doesn't change the problem but yes it's a nice idea.

Michael


>
> --
> Tom