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

[Roman Shaposhnik <roman@xxxxxxxxxx>]

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)
   2. booting via u-boot (with efiboot)
   3. booting via honest, upstream UEFI
(https://github.com/pftf/RPi4/releases/tag/v1.5)

So far we've been mostly doing #2 since it is the most flexible one.

Thanks,
Roman.