Re: [PATCH 1/1] efi_loader: stop watchdogs in ExitBootServices()

[Andre Przywara <andre.przywara@arm.com>]

On Tue, 9 Nov 2021 13:18:28 -0500
Tom Rini <trini@konsulko.com> wrote:

> On Tue, Nov 09, 2021 at 07:15:10PM +0100, Heinrich Schuchardt wrote:
> > On 11/9/21 18:55, Tom Rini wrote:  
> > > On Tue, Nov 09, 2021 at 11:19:01AM +0100, Heinrich Schuchardt wrote:
> > >   
> > > > The UEFI specification requires for ExitBootServices() that "the boot
> > > > services watchdog timer is disabled". We already disable the software
> > > > watchdog. We should additionally disable the hardware watchdogs.
> > > > 
> > > > Reported-by: Andre Przywara <andre.przywara@arm.com>
> > > > Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>  
> > > 
> > > Let me start by saying thank you for bringing this up with UEFI folks as
> > > well.  To be clear, for right now I would much rather see U-Boot
> > > continue to be non-complaint with UEFI in this regard and assume that a
> > > running watchdog will be able to be handled by the running OS (which
> > > tends to be the case, but not always as sunxi has just shown) than to
> > > attempt to be complaint with the spec as it stands now as I am hopeful
> > > that we can get this case handled in a way that matches long standing
> > > industry practice.
> > >   
> > 
> > We have either merge this patch or
> > 
> > [1/1] watchdog: don't autostart watchdog on Sunxi boards
> > https://patchwork.ozlabs.org/project/uboot/patch/20211105183431.117221-1-heinrich.schuchardt@canonical.com/
> > 
> > or we will be breaking boot processes that have been running up to now.
> > 
> > As Sunxi watchdogs were only enabled by a recent patch disabling autostart
> > should not cause any harm.  
> 
> Yes, I was expecting a PR from Andre in my inbox this morning with your

This was my plan as well, until I opened up the UEFI spec ;-)
Also I didn't see any problems so far in my - admittedly limited -
casual testing (because I boot quickly and have the WDT compiled in).

But I see it now when disabling the watchdog in the kernel, so will
take the "don't autostart" patch anyway.

If people have an embedded deployment where they rely on the watchdog,
they can surely enable it before building U-Boot.

Cheers,
Andre

> patch, as he had said he would apply it.  I'm just assuming now I got a
> bit ahead of myself with expecting it so quickly.
>