[PATCH 1/2] timer: tegra: Bind watchdog driver when timer node is processed

[Tom Rini]

On Tue, Sep 09, 2025 at 06:44:45PM +0300, Svyatoslav Ryhel wrote:
> вт, 9 вер. 2025 р. о 18:39 Tom Rini <trini at konsulko.com> пише:
> >
> > On Tue, Sep 09, 2025 at 02:26:19PM +0300, Svyatoslav Ryhel wrote:
> > > вт, 9 вер. 2025 р. о 13:15 Łukasz Majewski <lukma at nabladev.com> пише:
> > > >
> > > > Hi Svyatoslav,
> > > >
> > > > > пн, 8 вер. 2025 р. о 15:41 Łukasz Majewski <lukma at nabladev.com> пише:
> > > > > >
> > > > > > Hi Svyatoslav,
> > > > > >
> > > > > > > вт, 26 серп. 2025 р. о 12:39 Lukasz Majewski <lukma at nabladev.com>
> > > > > > > пише:
> > > > > > > >
> > > > > > > > The Tegra30 SoC is a bit special, as it doesn't have the
> > > > > > > > separate IP block to provide watchdog functionality.
> > > > > > > >
> > > > > > > > Instead, timer IP block allows such functionality when properly
> > > > > > > > configured.
> > > > > > > >
> > > > > > > > As in the tegra30.dtsi there is a timer node, which "covers" all
> > > > > > > > timers, with 'nvidia,tegra30-timer' compatibility it was
> > > > > > > > necessary to manually bind U-Boot's WDT driver (based on
> > > > > > > > WDT_UCLASS).
> > > > > > > >
> > > > > > > > Signed-off-by: Lukasz Majewski <lukma at nabladev.com>
> > > > > > > > ---
> > > > > > > >  drivers/timer/tegra-timer.c | 18 ++++++++++++++++++
> > > > > > > >  1 file changed, 18 insertions(+)
> > > > > > > >
> > > > > > >
> > > > > > > What is the practical application for this diver in therms of
> > > > > > > Tegra and U-Boot overall?
> > > > > >
> > > > > > You have the WDT functionality working. It uses the same DTS
> > > > > > bindings as ones used in Linux.
> > > > >
> > > > > Why do we need WDT for Tegra in U-Boot at all?
> > > >
> > > > Can you correct me if I draw wrong conclusion - you ask why Tegra needs
> > > > to support watchdog in u-boot bootloader ?
> > > >
> > > > > It is not used and has
> > > > > no practical application.
> > > > >
> > > >
> > > > Yes, it has ...
> > > >
> > > > Customer has number of Tegra30 colibri modules in the field. They want
> > > > to switch to u-boot + linux kernel BSP.
> > > >
> > > > For their application - it would be welcome if the device could reboot
> > > > and start emergency procedure in the case of not being able to start
> > > > Linux.
> > > >
> > > > The procedure is that we start Watchdog at very early boot - then we do
> > > > have for example 30 seconds to "feed" the Watchdog in Linux
> > > >
> > > > When we fail, after watchdog reboot, we can switch to another rootfs
> > > > partition (the A/B scheme of booting) or start emergency system.
> > > >
> > >
> > > So when are you going to submit this board variant? If driver has no
> > > users, it is removed.
> >
> > I assume it would be enabled on colibri_t30_defconfig.
> >
> 
> T30 colibri does not need it and does not use it with current
> configuration, hence I am asking about board submission.

It's a devkit where I'm pretty sure the watchdog exists, so we can
enable it there and be done. Just because it doesn't use it today
doesn't mean it can't use it in the future if we enable it, the "use
watchdog to make sure A/B system configures are stable" is a common use
case.

-- 
Tom
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 228 bytes
Desc: not available
URL: <https://lists.denx.de/pipermail/u-boot/attachments/20250909/d9617e91/attachment.sig>