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

[Łukasz Majewski]

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.


> > > Where is can be used so that existing means of
> > > U-Boot cannot handle such case?  
> >
> > Currently u-boot for Tegra 30 doesn't support Watchdog at all...  
> 
> Yes, and it does not affect or break anything.

Could you be more specific?

> 
> > You have for example collibri T30 modules without WDT functionality
> > support.  
> 
> Correct and? ALL Tegra devices work perfectly fine WITHOUT WDT

They will not fulfil requirements of my customer's use case...

> 
> > After adding those patches you can use WDT class (and wdt command)
> > to control WDT.
> >  
> 
> And what is the benefit? To have a driver for the sake of having a
> driver?

The benefit is simple - WDT support in u-boot allows my customer to
switch to open source BSP.

Many other SoCs (like NXP) do support Watchdog.

> 
> > Do you have more specific questions?
> >
> >
> > It is strange, but I've just noticed your reply (caused probably by
> > my "work" mail switch), so I would like to apologize for a late
> > reply.
> >
> >
> > --
> > Best regards,
> >
> > Lukasz Majewski
> >
> > --
> > Nabla Software Engineering GmbH
> > HRB 40522 Augsburg
> > Phone: +49 821 45592596
> > E-Mail: office at nabladev.com
> > Geschftsfhrer : Stefano Babic  



-- 
Best regards,

Lukasz Majewski

--
Nabla Software Engineering GmbH
HRB 40522 Augsburg
Phone: +49 821 45592596
E-Mail: office at nabladev.com
Geschftsfhrer : Stefano Babic