[PATCH v2 5/5] doc: board: document support for USB DFU boot on AM62Px SoC

[Siddharth Vadapalli]

On Wed, Dec 18, 2024 at 04:08:01PM +0200, Roger Quadros wrote:

Hello Roger,

> 
> 
> On 18/12/2024 14:45, Siddharth Vadapalli wrote:

[...]

> > +DFU based boot
> > +--------------
> > +
> > +To boot the board over DFU, set the switches to DFU mode and connect to the
> > +USB type C DRD port on the board. After power-on the build artifacts needs to be
> > +uploaded one by one with a tool like dfu-util.
> > +
> > +The initial ROM will have a DFU alt named `bootloader` for the initial R5 spl
> > +upload. The next stages as exposed by U-Boot have target alts matching the name
> > +of the artifacts, for these a USB reset has to be done after each upload.
> > +
> > +When using dfu-util the following commands can be used to boot to a U-Boot shell:
> > +
> > +.. prompt:: bash $
> > +
> > +  dfu-util -a bootloader -D tiboot3.bin
> > +  dfu-util -R -a tispl -D tispl.bin
> > +  dfu-util -R -a u-boot.img -D u-boot.img
> 
> Is there a known reason why -R was not used for the first command but required in last two?
> What about if -R is not used for all 3 commands?

According to the "dfu-util" help menu, the "-R" option is defined as:
"Issue USB Reset signalling once we're finished"

While the "-R" option is not required in the first stage / command, it
is required in the next stages. Without "-R", the user would have to
press "Ctrl+C" to proceed i.e. tispl.bin / u-boot.img are transferred
/ downloaded onto the device but not executed until user presses "Ctrl+C".

As to why "-R" is not required in the first stage, I suppose that ROM
automatically executes tiboot3.bin after it has been transferred.

Regards,
Siddharth.