linux-kernel - RE: [PATCH v3 5/6] watchdog: rzv2h_wdt: Add support to retrieve the bootstatus information

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Message-ID:
 <TY3PR01MB113464F4DA8BEB9041395904F86182@TY3PR01MB11346.jpnprd01.prod.outlook.com>
Date: Tue, 14 Jan 2025 11:09:05 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
CC: Geert Uytterhoeven <geert+renesas@...der.be>, Michael Turquette
	<mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, Rob Herring
	<robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
	<conor+dt@...nel.org>, Wim Van Sebroeck <wim@...ux-watchdog.org>, Guenter
 Roeck <linux@...ck-us.net>, Magnus Damm <magnus.damm@...il.com>, Wolfram Sang
	<wsa+renesas@...g-engineering.com>, "linux-renesas-soc@...r.kernel.org"
	<linux-renesas-soc@...r.kernel.org>, "linux-clk@...r.kernel.org"
	<linux-clk@...r.kernel.org>, "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-watchdog@...r.kernel.org"
	<linux-watchdog@...r.kernel.org>, Fabrizio Castro
	<fabrizio.castro.jz@...esas.com>, Prabhakar Mahadev Lad
	<prabhakar.mahadev-lad.rj@...renesas.com>
Subject: RE: [PATCH v3 5/6] watchdog: rzv2h_wdt: Add support to retrieve the
 bootstatus information


Hi Prabhakar,

> -----Original Message-----
> From: Lad, Prabhakar <prabhakar.csengg@...il.com>
> Sent: 14 January 2025 10:57
> Subject: Re: [PATCH v3 5/6] watchdog: rzv2h_wdt: Add support to retrieve the bootstatus information
> 
> Hi Biju,
> 
> On Tue, Jan 14, 2025 at 9:55 AM Biju Das <biju.das.jz@...renesas.com> wrote:
> >
> > Hi Prabhakar,
> >
> > Thanks for the patch.
> >
> > > -----Original Message-----
> > > From: Prabhakar <prabhakar.csengg@...il.com>
> > > Sent: 13 January 2025 11:24
> > > Subject: [PATCH v3 5/6] watchdog: rzv2h_wdt: Add support to retrieve
> > > the bootstatus information
> > >
> > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > >
> > > On the RZ/V2H(P) SoC we can determine if the current boot is due to
> > > `Power-on-Reset` or due to the `Watchdog`. The information used to determine this is present on
> the CPG block.
> > >
> > > The CPG_ERROR_RSTm(m = 2 - 8) registers are set in response to an error interrupt causing an
> reset.
> > > CPG_ERROR_RST2[ERROR_RST0/1/2] is set if there was an
> > > underflow/overflow on WDT1 causing an error interrupt.
> > >
> > > To fetch this information from CPG block `syscon` is used and
> > > bootstatus field in the watchdog device is updated based on the
> > > CPG_ERROR_RST2[ERROR_RST0/1/2] bit. Upon consumig CPG_ERROR_RST2[ERROR_RST0/1/2] bit we clear it.
> >
> > As syscon-cpg is available, can we get rid of Linux assuming
> > TF_A/U-boot for configuring Error Reset Select Registers(0x10420B04)for the watchdog to reset the
> system?
> >
> Agreed.
> 
> > After this, each watchdog device node will have, selection{offset,bit}
> > status{ offset,bit} renesas,syscon-cpg-error-rst-sel = <&cpg 0xb04 1>;
> > renesas,syscon-cpg-error-rst = <&cpg 0xb40 1>;
> >
> > Or
> >
> > renesas,syscon-cpg-error-rst = < &cpg 0xb04 1 0xb40 1>;
> >
> As we already have 0xb40 we can do 0xb40 - 0x3c to get `0xb04` in the WDT driver and the same bit
> numbers can be re-used for CPG_ERRORRST_SEL2,  so by this way we can avoid adding another property in
> DT. And I think this works for G3E too?

Yes, as there is 1:1 map between CPG_ERRORRST_SELm and CPG_ERROR_RSTm registers.

Cheers,
Biju