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

["Łukasz Majewski" <lukma@nabladev.com>]

Hi Tom,

> On Tue, Sep 09, 2025 at 06:44:45PM +0300, Svyatoslav Ryhel wrote:
> > вт, 9 вер. 2025 р. о 18:39 Tom Rini <trini@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@nabladev.com>
> > > > пише:  
> > > > >
> > > > > Hi Svyatoslav,
> > > > >  
> > > > > > пн, 8 вер. 2025 р. о 15:41 Łukasz Majewski
> > > > > > <lukma@nabladev.com> пише:  
> > > > > > >
> > > > > > > Hi Svyatoslav,
> > > > > > >  
> > > > > > > > вт, 26 серп. 2025 р. о 12:39 Lukasz Majewski
> > > > > > > > <lukma@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@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.

+1

-- 
Best regards,

Lukasz Majewski

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