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

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Message-ID:
 <TY3PR01MB11346643236A64D41150E4CC0863B2@TY3PR01MB11346.jpnprd01.prod.outlook.com>
Date: Mon, 16 Dec 2024 15:08:01 +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: 16 December 2024 13:14
> Subject: Re: [RFC PATCH] watchdog: rzv2h_wdt: Add support to retrieve the bootstatus information
> 
> Hi Biju,
> 
> On Sun, Dec 15, 2024 at 9:15 AM Biju Das <biju.das.jz@...renesas.com> wrote:
> >
> > 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-b5ac8c219e9
> > > > 6@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??
> >
> No, it doesn't work either; the CPG node block needs to have `syscon` compatible when you are using
> syscon_node_to_regmap/syscon_regmap_lookup_by_phandle. See patch [0] in `device_node_get_regmap()` the
> `of_syscon_register()` is only called when it has a `syscon` compatible or else `-EINVAL` is returned.
> 
> [0] https://lore.kernel.org/all/20241211-syscon-fixes-v1-3-b5ac8c219e96@kernel.org/

Not sure the patch series, intention is to support only external regmap 
for those who does not have "syscon" compatible??

I thought the intention was, without "syscon" compatible, still it creates internal regmap,
based on reg property of the system controller device node.

Cheers,
Biju