Re: [PATCH] xen/rpi4: implement watchdog-based reset

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 4 Jun 2020, Roman Shaposhnik wrote:
> On Thu, Jun 4, 2020 at 9:36 AM Julien Grall <julien@xxxxxxx> wrote:
> >
> > Hi,
> >
> > On 04/06/2020 17:24, Stefano Stabellini wrote:
> > > On Thu, 4 Jun 2020, André Przywara wrote:
> > >> On 04/06/2020 09:48, Julien Grall wrote:
> > >>
> > >> Hi,
> > >>
> > >>> On 03/06/2020 23:31, Stefano Stabellini wrote:
> > >>>> Touching the watchdog is required to be able to reboot the board.
> > >>>
> > >>> In general the preferred method is PSCI. Does it mean RPI 4 doesn't
> > >>> support PSCI at all?
> > >>
> > >> There is mainline Trusted Firmware (TF-A) support for the RPi4 for a few
> > >> months now, which includes proper PSCI support (both for SMP bringup and
> > >> system reset/shutdown). At least that should work, if not, it's a bug.
> > >> An EDK-2 build for RPi4 bundles TF-A automatically, but you can use TF-A
> > >> without it, with or without U-Boot: It works as a drop-in replacement
> > >> for armstub.bin. Instruction for building it (one line!) are here:
> > >> https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git/tree/docs/plat/rpi4.rst
> > >>
> > >>>>
> > >>>> The implementation is based on
> > >>>> drivers/watchdog/bcm2835_wdt.c:__bcm2835_restart in Linux.
> > >>>
> > >>> Can you give the baseline? This would allow us to track an issue and
> > >>> port them.
> > >>
> > >> Given the above I don't think it's a good idea to add extra platform
> > >> specific code to Xen.
> > >
> > > The RPi4, at least the one I have, doesn't come with any TF, and it
> > > doesn't come with PSCI in device tree. As a user, I would rather have
> > > this patch (even downstream) than having to introduce TF in my build and
> > > deployment just to be able to reboot.
> >
> > So what are you using for the firmware? Do you boot Xen directly?
> 
> You've got 3 options:
>    1. booting directly (see Dornernerworks build:
> https://github.com/dornerworks/xen-rpi4-builder/blob/master/rpixen.sh#L143)

Ah! I didn't realize they were booting directly, nice!