linux-kernel - Re: [PATCH 1/6] clk: renesas: r9a06g032: Enable the watchdog reset sources

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Date:   Wed, 9 Feb 2022 19:24:49 +0100
From:   Jean-Jacques Hiblot <jjhiblot@...phandler.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
CC:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/6] clk: renesas: r9a06g032: Enable the watchdog reset
 sources

Hi Geert,

On 08/02/2022 11:35, Geert Uytterhoeven wrote:
> Hi Jean-Jacques,
>
> On Tue, Feb 8, 2022 at 11:25 AM Jean-Jacques Hiblot
> <jjhiblot@...phandler.com> wrote:
>> On 07/02/2022 16:34, Geert Uytterhoeven wrote:
>>> On Fri, Feb 4, 2022 at 5:18 PM Jean-Jacques Hiblot
>>> <jjhiblot@...phandler.com> wrote:
>>>> The watchdog reset sources are not enabled by default.
>>>> Enabling them here to make sure that the system resets when the watchdog
>>>> timers expire.
>>>>
>>>> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@...phandler.com>
>>> Thanks for your patch!
>>>
>>> R-Car Gen3 and RZ/G2 SoCs have a similar mechanism.
>>> On these SoCs, the boot loader takes care of the configuration, as this
>>> is a system policy that goes beyond the Linux realm.
>>> Perhaps the RZ/N1 boot loader can do the same?
>>>
>>> Gr{oetje,eeting}s,
>> Thanks for you reviews and comments.
>>
>> I'm not conformable with the idea that the safety induced by the
>> watchdog is removed because the bootloader didn't set the register.
> What if the CM33 is the master, and the CM33 just wants to receive an
> interrupt when one of the CA7 watchdog timers times out?

In the next version of the patch I removed the part that enables the 
reset source.

However I kept the part that disables the reset source when the system 
is halted

because the system would otherwise reboot when a watchdog expires. Do you

see a scenario where this could be a problem ?

JJ

>
>> I'd rather that the kernel is able to enable the watchdog reset source.
>> If it is acceptable, we could use a new DTS entry to force the policy.
> DT describes hardware. not software policy.
> Although I agree e.g. the watchdog timeout value is software policy.

>
> 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