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

From: Aurelien Jarno <aurelien@aurel32.net>
To: Anand Moon <linux.amoon@gmail.com>
Cc: Samuel Holland <samuel.holland@sifive.com>,
	Troy Mitchell <troy.mitchell@linux.dev>,
	Vivian Wang <wangruikang@iscas.ac.cn>,
	Paul Walmsley <pjw@kernel.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Alexandre Ghiti <alex@ghiti.fr>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC] riscv: disable local interrupts and stop other CPUs before restart
Date: Sun, 26 Apr 2026 14:20:54 +0200	[thread overview]
Message-ID: <ae4DJnPhTNZzah4p@aurel32.net> (raw)
In-Reply-To: <CANAwSgR-rJ0O9SJc92z05NVez6ZSfn9Gx8fJr3Be3QfCpR_XBA@mail.gmail.com>

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

Regards
Aurelien

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

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv