linux-kernel - Re: [PATCH v4 7/9] watchdog: rzv2h_wdt: Configure CPG_ERRORRST

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Message-ID: <CAMuHMdWb_dT3j8YcHWbzsYVPycq_gmA8Wh+ddTd6QdMBg01FHg@mail.gmail.com>
Date: Thu, 20 Feb 2025 11:20:32 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Prabhakar <prabhakar.csengg@...il.com>
Cc: 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-clk@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-watchdog@...r.kernel.org, Biju Das <biju.das.jz@...renesas.com>, 
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH v4 7/9] watchdog: rzv2h_wdt: Configure CPG_ERRORRST_SEL2 register

Hi Prabhakar,

On Mon, 10 Feb 2025 at 19:49, Prabhakar <prabhakar.csengg@...il.com> wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
>
> Currently, the watchdog driver relies on TF-A/U-Boot to configure the
> `CPG_ERRORRST_SEL2` register. This register must be set correctly to
> ensure a reset request is issued upon watchdog timer (WDT) underflow.
>
> Now that the driver has access to the `syscon` handle for CPG, configure
> `CPG_ERRORRST_SEL2` directly instead of depending on firmware. This
> improves robustness by ensuring the required configuration is applied
> within the driver itself.
>
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>

Thanks for your patch!

IMHO doing it in the firmware stack is actually a good thing, as the
watchdog policy is system-wide, and thus goes beyond Linux running on
the application cores.

That is also the reason why commit 76b1c5b218f31811 ("[TEST] soc:
renesas: rcar-rst: Enable WDT reset on early R-Car V4M") is only
part of renesas-drivers[1], and not planned for upstream.  The sole
exception on modern R-Car is R-Car V3U, cfr. commit cb9a39aacd3d6387
("soc: renesas: rcar-rst: Allow WDT reset on R-Car V3U")[2].

[1] https://git.kernel.org/pub/scm/linux/kernel/git/geert/renesas-drivers.git/commit/?h=renesas-drivers-2025-02-18-v6.14-rc3&id=76b1c5b218f31811a7aaca588d3ec4ba584b7bf2
[2] https://elixir.bootlin.com/linux/v6.13.3/source/drivers/soc/renesas/rcar-rst.c#L76

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds