kwboot: Marvell Dove UART booting

[Tony Dinh]

Hi Pali,

On Sat, Jan 1, 2022 at 1:53 PM Pali Rohár <pali at kernel.org> wrote:
>
> On Sunday 26 December 2021 13:41:03 Tony Dinh wrote:
> > Follow up on the UART booting session before.
> >
> > Thanks for the advice about the Reset Strapping documentation. I've
> > extracted the attachment 88AP510_Reset_Strapping.xls from the HW Spec
> > for Dove at:
> > https://www.kernel.org/doc/html/latest/arm/marvell.html
> >
> > Listed below are the Boot Modes that are relevant to this subject
> > (there are other Boot Modes for SATA, NAND but we are not interested
> > in those):
> >
> > 0x00 Direct boot from SPI
> > 0x01 Boot from SPI with 3 address cycles
> > 0x02 Boot from SPI with 4 address cycles
> > 0x0E Boot from UART0 using Xmodem
> > 0x0F Boot from UART1 using Xmodem
> > 0x10 Open BootROM debug prompt on UART0
> > 0x11 Open BootROM debug prompt on UART1
> >
> > So it does look like the jumper on this HP T5335z is actually to put
> > the box into BootROM debug mode using 0x10. And from there, we can use
> > 0x0E to put the BootROM into UART0 booting mode.
> >
> > Oddly, I've also tried booting from SPI while at the BootROM debug
> > prompt, but have not been successful with either 0x00, 0x01, or 0x02.
> > I was hoping that it would make testing easier if I could run "Boot
> > from SPI" to boot into Linux without having to remove the jumper.
>
> And which hex mode is activated when jumper is not set to that Debug
> prompt UART mode? You should be able to check current mode by reading
> 0xD00D0214 address which should contain latched sample at reset value.
> E.g. in U-Boot by 'md 0xD00D0214 1' command.

Without the jumper inserted, it was set to 0x00.

HP>> md 0xD00D0214 1
d00d0214: 00000000    ....

So while I went back to debug mode with the jumper inserted, and tried
to switch to boot mode 0x00
Bootstrap 2.33>x 0x00

Nothing happened, so I hit another <Enter>, and it went back to the
debug prompt:
Bootstrap 2.33>

I also repeated a second time. While at the debug prompt, I removed
the jumper, and then
Bootstrap 2.33>x 0x00

Nothing happened, too. It seems to be stuck in debug mode. The only
way I can proceed is to set the boot mode to UART, exit the serial
console, and run kwboot.  And of course, recycling the power to get it
back to normal booting from SPI.

Thanks,
Tony