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

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Date:   Wed, 13 Jul 2022 14:08:58 +0200
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Michael Walle <michael@...le.cc>,
        Steen Hegelund <steen.hegelund@...rochip.com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Lars Povlsen <lars.povlsen@...rochip.com>,
        Clément Léger <clement.leger@...tlin.com>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>,
        Kavyasree Kotagiri <kavyasree.kotagiri@...rochip.com>,
        Horatiu Vultur <horatiu.vultur@...rochip.com>
Subject: Re: [PATCH] Revert "reset: microchip-sparx5: allow building as a
 module"

Hi,

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.

[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

regards
Philipp