Re: [PATCH u-boot v2 1/2] drivers: spi: Add support for disabling FMC_WDT2 for aspeed

Andrew Jeffery
2026-01-12T01:12:04Z

On Tue, 2026-01-06 at 17:52 +0300, Ivan Mikhaylov wrote:
> On Tue, Jan 6, 2026 at 3:05 AM Marc Olberding <molberding@nvidia.com> wrote:
> >
> > On Sat, Jan 03, 2026 at 12:24:07AM +0300, Иван Михайлов wrote:
> > > On Wed, Dec 3, 2025 at 2:53 AM Marc Olberding <molberding@nvidia.com> wrote:
> > > >
> > > > Adds support for disabling the ast2600 FMC_WDT2 through
> > > > a device tree entry in the fmc node.
> > > > Set `aspeed,watchdog-disable` in your device tree to have
> > > > the driver disable it.
> > >
> > > Marc, FMC_WDT2 doesn't disable watchdog, it controls ABR mode.
> > > Watchdog with or without ABR still in operational mode.
> > > So, maybe aspeed,abr-disable?
> > >
> > > Below namings probably should be corrected.
> > We aren't disabling ABR mode with this change, right? That's only
> > done through hardware straps or OTP changes. All this is doing is clearing bit 0
> > of FMC64, which per the datasheet disables the watchdog. The idea here is
> > to just allow boot to progress normally, without the watchdog. For ping pong update,
> > userspace can flash the alternative SPI and re-enable the watchdog timer on complete,
> > and the BMC will boot from the new image upon reset. Let me know if I'm misunderstanding
> > your comment.
> >
>
> Marc, when you clrbits_le on FMC64/FMC_WDT2, then you disable ABR mode, I
> assume you can check it with evb board or ast2600-a3 to prove. On my board
> ast2600-a3 it works in that way I described with enabled OTP strap for ABR.

Can you elaborate on the sequences involved?

The reset definitions for the FMC suggest it's affected by an ARM
reset, which should in-turn reinitialise FMC_WDT2 and follow the boot
flow to enable the ABR again. In my understanding disabling it in
firmware shouldn't prevent ABR operations subsequent to future resets?

Further, the aspeed,watchdog-disable property is to be taken in the
context of the node with the FMC compatible string, referring to the
FMC's watchdog and not the (separate) SoC watchdogs. However the FMC
does have multiple watchdogs, one for address mode detection and the
other for ABR. So maybe the name of the property could be improved in
that regard. I think it's still reasonable to have watchdog in the
name. My immediate reaction is that "aspeed,abr-disable" overstates its
behaviour. How about "aspeed,abr-watchdog-disable"? Previous
suggestions were "fmc-wdt2-disable", and the current "aspeed,watchdog-
disable"

>
> Also description of it in 14.2.2 Alternative Boot Recovery Function.

The second bullet in that section says:

When the firmware booting successfully, it should disable FMC_WDT2
to stop booting switch

This is what Marc is trying to achieve by providing the property. Other
platforms may want to make the choice elsewhere.

Andrew