linux-kernel - RE: [RFC PATCH] watchdog: rzv2h_wdt: Add support to retrieve the bootstatus information

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Message-ID:
 <TY3PR01MB1134664B737514AEAECA960D9863A2@TY3PR01MB11346.jpnprd01.prod.outlook.com>
Date: Sun, 15 Dec 2024 09:15:48 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
CC: Guenter Roeck <linux@...ck-us.net>, Wim Van Sebroeck
	<wim@...ux-watchdog.org>, Philipp Zabel <p.zabel@...gutronix.de>, Geert
 Uytterhoeven <geert+renesas@...der.be>, Rob Herring <robh@...nel.org>,
	"linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>, Prabhakar Mahadev Lad
	<prabhakar.mahadev-lad.rj@...renesas.com>
Subject: RE: [RFC PATCH] watchdog: rzv2h_wdt: Add support to retrieve the
 bootstatus information

Hi Prabhakar,

> -----Original Message-----
> From: Lad, Prabhakar <prabhakar.csengg@...il.com>
> Sent: 14 December 2024 21:36
> Subject: Re: [RFC PATCH] watchdog: rzv2h_wdt: Add support to retrieve the bootstatus information
> 
> Hi Biju,
> 
> On Sat, Dec 14, 2024 at 11:32 AM Biju Das <biju.das.jz@...renesas.com> wrote:
> >
> > Hi Lad, Prabhakar,
> >
> <snip>
> > > > That is a change in behavior. Up to now the syscon phandle did not
> > > > have to exist for the driver to work. Is it guaranteed to not
> > > > result in regressions on systems where it doesn't ? Also, is this
> > > > documented ? I don't seem to be able to
> > > find it.
> > > >
> > > Agreed. I will add a fallback mechanism to handle cases where the
> > > syscon property is not present in the WDT node. This will ensure no
> > > regressions occur, and the bootstatus will simply be set to 0 in
> > > such scenarios. As mentioned in the patch comments, I have not yet
> > > submitted the DT binding changes because I wanted feedback on the syscon approach. The new RZ SoCs
> have registers scattered across various locations, and I was exploring if there might be a better way
> to handle this.
> >
> > See, syscon compatible not needed with [1]
> >
> > [1]
> > https://lore.kernel.org/all/20241211-syscon-fixes-v1-3-b5ac8c219e96@ke
> > rnel.org/
> >
> As per my understanding, `syscon` compatible is required in this case because the CPG driver does not
> register a regmap. With the patch [1] (linked above), this applies to drivers that register a syscon
> regmap, where the corresponding DT node does not necessarily need a `syscon` compatible.

I guess you can use "syscon_node_to_regmap" for that as of_syscon_register_regmap() is for externally
created regmaps??

syscon_regmap_lookup_by_phandle() in turn call syscon_node_to_regmap()

Cheers,
Biju