Re: [PATCH 2/2] ARM: imx: src: support vf610 system reset controller

[Guenter Roeck]

On 11/28/2014 03:00 PM, Stefan Agner wrote:
> On 2014-11-28 23:22, Arnd Bergmann wrote:
> > On Friday 28 November 2014 23:09:09 Stefan Agner wrote:
> > > On 2014-11-28 22:24, Arnd Bergmann wrote:
> > > > On Friday 28 November 2014 22:02:01 Stefan Agner wrote:
> > > >
> > > > > > If the SRC is also capable of resetting individual blocks instead of just
> > > > > > the entire machine, it would be a reset driver in drivers/reset instead.
> > > > >
> > > > > Beside the system reset, there is only a mask functionality for the
> > > > > watchdogs (there are two watchdogs, one for Cortex-A5 and one for the
> > > > > M4). This makes the SRC module in the Vybrid a bit different then what
> > > > > is available on other i.MX SoC's...
> > > >
> > > > If you already have the watchdog registers in there and want to have
> > > > a watchdog driver too, the easiest way would be to register the reboot
> > > > handler from the watchdog driver.
> > >
> > > Hm, not sure we speak about the same here. The SRC module has two
> > > (multi-)bit fields to mask the watchdog reset event for each watchdog.
> > > Beside that, there are two full watchdog register maps, which are in
> > > different areas. There is already a driver for this watchdogs. I'm not
> > > sure what the idea behind this is exactly, I guess it would easily allow
> > > to (temporary) mask the other CPU's watchdog. However, I don't think we
> > > need that functionality, so I don't care about that right now.
> >
> > Ok, I see, thanks for the clarification!
> >
> > > There is also a restart handler in the watchdog driver, but I prefer to
> > > use the reset capabilities of the SRC since it has immediate effect.
> > >
> > > Lets get to the big picture again: I could register the whole SRC
> > > register map as a syscon device and then access the registers from my
> > > suspend/resume implementation later on. And similar in the restart
> > > driver, I would use syscon_regmap_lookup_by_compatible to check if it
> > > contains the vf610-src compatible string and register the restart
> > > driver/handler if available.
> >
> > Correct, and also in the watchdog driver, I guess.
> >
> > Instead of syscon_regmap_lookup_by_compatible, please use
> > syscon_regmap_lookup_by_phandle and put the link to the syscon
> > device into the device accessing it.
> >
> > Also, see if you can use or extend drivers/power/reset/syscon-reboot.c
> > for your use case.
>
> Nice, this allows to do the reset with almost no code. The only thing
> which might be a problem is the priority: I used 192 since 128 is
> already used by the watchdog driver. Maybe we can change that
> syscon-reboot is a bit above watchdogs by default, or maybe even a dt
> property? I will try to use that driver for v2. Thx!

A dt property might make more sense if the syscon driver is to be used
for multiple systems. Otherwise, no matter what you pick, it will be
wrong for some system.

Guenter

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