Re: [PATCH RFC] riscv: disable local interrupts and stop other CPUs before restart

Anand Moon
2026-04-27T03:47:36Z

Hi Aurelien,

On Sun, 26 Apr 2026 at 17:51, Aurelien Jarno <aurelien@aurel32.net> wrote:
>
> Hi Anand,
>
> On 2026-04-25 23:12, Anand Moon wrote:
> > Hi All,
> >
> > On Fri, 24 Apr 2026 at 02:21, Aurelien Jarno <aurelien@aurel32.net> wrote:
> > >
> > > Hi,
> > >
> > > On 2026-03-16 08:19, Samuel Holland wrote:
> > > > Hi Troy,
> > > >
> > > > On 2026-03-16 2:23 AM, Troy Mitchell wrote:
> > > > >> I think the reason we ended up with the "unsafe" implementations of the
> > > > >> reboot/shutdown functions is that on the backend it is usually SBI SRST
> > > > >> calls, which can protect itself from other CPUs and interrupts. Since on
> > > > >> K1 we're going to be poking I2C directly, we run into the problem
> > > > >> described above. So all of these should disable interrupts and stop
> > > > >> other CPUs before calling the handlers, and can't assume the handlers
> > > > >> are all SBI SRST.
> > > > > Yes, we cannot assume that all platforms rely on this.
> > > >
> > > > Why isn't K1 using the SBI SRST extension? Resetting the platform from S-mode
> > > > directly causes problems if you ever want to run another supervisor domain (for
> > > > example a TEE or EFI runtime services), which may need to clean up before a
> > > > system reset.
> > > >
> > > > As you mention, other platforms use the standard SBI SRST interface, event if
> > > > they need to poke a PMIC to perform a system reset. Is there something
> > > > preventing K1 from following this path?
> > >
> > > I went this path and submitted a patchset to OpenSBI mailing list doing
> > > that:
> > > https://lore.kernel.org/opensbi/20260419150857.2705843-1-aurelien@aurel32.net/T/#t
> > >
> > I just wanted to check if we can use the latest OpenSBI image with
> > vendor u-boot ?
> > If so, can you share the details of flash the u-boot and OpenSBI binaries? .
>
> That is a good question, and no this doesn't work out of the box.
>
> > I was working on the watchdog driver, and the system hangs at reboot
> > So, what changes do we need to make in OpenSBI to handle this issue?
>
> This can be addressed either by making OpenSBI compatible with the
> vendor U-Boot, or by making the vendor U-Boot compatible with the
> upstream OpenSBI. On my side, I prefer the latter option as it also
> keeps the upstream OpenSBI compatible with the (future) upstream U-Boot.
>
> I have just published a blog post about how to do that:
> https://blog.aurel32.net/upstream-opensbi-spacemit-k1.html
>
Thanks for the update.

> Regards
> Aurelien
>
Thanks
-Anand
> --
> Aurelien Jarno GPG: 4096R/1DDD8C9B
> aurelien@aurel32.net http://aurel32.net