Re: [PATCH] Revert "reset: microchip-sparx5: allow building as a module"

[Michael Walle]

Hi,

Am 2022-07-13 14:08, schrieb Philipp Zabel:
> On Mi, 2022-07-13 at 11:52 +0200, Michael Walle wrote:
> > [+ Horatiu, I missed you earlier, sorry]
> >
> > Hi Steen,
> >
> > Am 2022-07-13 11:40, schrieb Steen Hegelund:
> > > I am afraid that the exact list of affected modules is not available,
> > > so using the
> > > RESET_PROT_STAT.SYS_RST_PROT_VCORE bit is the best known way of
> > > resetting as much as possible, and
> > > still continue execution.
> >
> > Mh, you are designing that chip (at least the LAN966x) no? Shouldn't
> > that information be available anywhere at Microchip? ;)
> >
> > Anyway, it looks like almost the whole chip is reset
> > except some minor things. So the driver has actually a
> > wrong name. Until recently only the switch driver was the
> > sole user of it (at least on the lan966x). So, my question
> > remains, is this correct? I mean the switch driver says,
> > "reset the switch core", but what actually happens is that
> > the the entire SoC except the CPU and maybe the io mux is reset.
> > What about the watchdog for example? Will that be reset, too?
>
> If [1-3] are to be trusted, RESET_PROT_STAT[VCORE_RST_PROT_WDT], which
> protects the watchdog from soft reset, is not set by default. So yes?
>
> There are also AMBA, PCIe, PDBG protection bits against Vcore soft
> reset in this register, depending on the platform.

*But* this also prevents it from reset by the watchdog. I don't know
if we want that?!

I.e. what happens if one sets RESET_PROT_STAT[VCORE_RST_PROT_WDT] and
the watchdog does a reset? OTHO, I guess it is also bad to reset the
watchdog during boot.. IMHO this reset logic doesn't look that well
designed.

> [1] 
> https://microchip-ung.github.io/sparx-5_reginfo/reginfo_sparx-5.html?select=cpu,cpu_regs,reset_prot_stat
> [2] 
> https://microchip-ung.github.io/lan9662_reginfo/reginfo_LAN9662.html?select=cpu,cpu_regs,reset_prot_stat
> [3] 
> https://microchip-ung.github.io/lan9668_reginfo/reginfo_LAN9668.html?select=cpu,cpu_regs,reset_prot_stat

-michael