[U-Boot] [PATCH v2 2/3] arm: zynq: Wire watchdog internals

[Michal Simek]

Hi,


>
> >
> > >
> > > During update the not serviced watchdog reset the board and you may
> > > end up with brick.
> > >
> >
> > Depends on your setup and needs.  If you have board with only one
> > watchdog when you boot from qspi but
> > reading variables from qspi failed (for whatever reason). it means
> > u-boot ends in prompt watchdog is serviced
> > properly and it will never expire.
>
> The most WDT use cases is to reboot when the target device aborts
> (hangs) at program execution.
>
> ( As a remedy one can put reset if bootx fails ).
>
> However, I do get your point.
>


WDT is also wired with sysreset where you can use watchdog ability to reset
the system.
It can be in case of reset command itself or panic for example.

But it is not only about reboot. On ZynqMP it can be IRQ to different unit
on the system.




>
> > But in this case this is broken
> > boot. In next reset variable read can be correct.
> >
> >
> >
> > >
> > > > It should enable you and option to boot till
> > > > certain time or reboot.
> > >
> > > You can enable WDT in SPL and "refresh" it in u-boot if needed.
> > >
> >
> > I didn't try SPL but I will look at it. Again depends on use case you
> > have. Also which board you are using. If you have one or multiple
> > watchdogs. I can imagine if you have 2 watchdogs available that one
> > will cover full boot till linux and
> > one just u-boot issues.
> >
>
> I'm not sure if u-boot now supports two watchdogs in a generic way...
>

With DM based drivers this should be possible.


>
> >
> >
> > >
> > > > I have tested that this setting is working. I haven't tested if
> > > > Linux cadence driver can handle it but that's different topic.
> > >
> > > There are several options in Linux (with iMX6 at least).
> > >
> > > You may disable WDT when driver is correctly setup, refresh it  or
> > > leave as is, so user space program can take over the WDT control.
> > >
> >
> >
> > I expect this behaviour but I just didn't test that with cadence
> > driver. Also initial u-boot setup can be different compare to OS
> > setup.
>
> Yes, agree. It is use case dependent.
>

Good.

Thanks,
Michal


-- 
Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel - Microblaze cpu - http://www.monstr.eu/fdt/
Maintainer of Linux kernel - Xilinx Zynq ARM architecture
Microblaze U-BOOT custodian and responsible for u-boot arm zynq platform