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

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Message-ID: <CA+V-a8vrhb7Wt4RwQJ1wpDYfiy8-jiT0Dej7UYcRszyS9cKx4g@mail.gmail.com>
Date: Tue, 14 Jan 2025 10:57:20 +0000
From: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To: Biju Das <biju.das.jz@...renesas.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 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?

Cheers,
Prabhakar