[U-Boot] Unable to boot evb-ast2500

[Joel Stanley]

On Mon, 6 Aug 2018 at 19:39, Cédric Le Goater <clg at kaod.org> wrote:
>
> On 08/06/2018 05:25 AM, Joel Stanley wrote:
> > Hello,
> >
> > I am attempting to boot evb-ast2500 in Qemu before flashing it to a
> > system. It doesn't get past the DRAM step, due to getting stuck
> > endlessly looping in some libfdt code.
> >
> > With some debugging turned on, I get this:
> >
> > OF: translating address: 0040781e
> > OF: parent translation for: 00000000
> > OF: one level translation: 0040781e
> > OF: parent translation for: 00000000
> > OF: one level translation: 0040781e
> > OF: translating address: 00206e1e
> >
> >
> > U-Boot 2018.09-rc1-00096-gbb694d4e898b-dirty (Aug 06 2018 - 12:27:22 +0930)
> >
> > Model: Aspeed BMC
> > DRAM:  OF: translating address: 00006e1e
> > OF: translating address: 00026e1e
> > OF: translating address: 0050781e
> > OF: parent translation for: 00000000
> > OF: one level translation: 0050781e
> > OF: parent translation for: 00000000
> > OF: one level translation: 0050781e
> > Watchdog timer expired.
> >
> > And then the watchdog causes the system to reboot. The build is master
> > as of gbb694d4e898b, with the addition of some #define DEBUG.
> >
> > I don't think this is a qemu issue. If it is, I can work on fixing
> > qemu, but I need some help on understanding what u-boot is doing.
>
> The sdram driver in U-Boot uses the watchdog1 and the SCU power
> reset register to reset the SDRAM controller. Our QEMU emulation
> is not precise enough I think.

Thanks for the pointer.

I was able to get u-boot to load to the prompt after some hacks to get
rid of the watchdog requirement. It was a surprise to find out that
the watchdog is used to reset the SDRAM controller!

I have some patches to send to the qemu list that will allow it to run.

Cheers,

Joel