linux-kernel - Re: [PATCH] clk: renesas: r9a07g044: Add WDT2 clocks to critical list

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Message-ID: <CAMuHMdU0BSByCZynkdhDQNcQ+7UT=YgZLe_YNVR4d=dS=2mX=g@mail.gmail.com>
Date:   Thu, 6 Oct 2022 10:15:48 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     "Lad, Prabhakar" <prabhakar.csengg@...il.com>,
        Biju Das <biju.das.jz@...renesas.com>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH] clk: renesas: r9a07g044: Add WDT2 clocks to critical list

Hi Prabhakar, Biju,

On Wed, Oct 5, 2022 at 2:56 PM Lad, Prabhakar
<prabhakar.csengg@...il.com> wrote:
> On Wed, Oct 5, 2022 at 9:27 AM Biju Das <biju.das.jz@...renesas.com> wrote:
> > > > On Mon, Sep 19, 2022 at 2:52 PM Biju Das <biju.das.jz@...renesas.com> wrote:
> > > > > > On Mon, Sep 19, 2022 at 2:35 PM Biju Das <biju.das.jz@...renesas.com> wrote:
> > > > > > > > From: Lad Prabhakar <prabhakar.mahadev-
> > > lad.rj@...renesas.com>
> > > > > > > > Add the WDT2 clocks to r9a07g044_crit_mod_clks[] list as WDT CH2 is
> > > > > > > > specifically to check the operation of Cortex-M33 CPU on the
> > > > > > > > RZ/{G2L, G2LC, V2L} SoCs and we dont want to turn off the clocks of
> > > > > > > > WDT2 if it isn't enabled by Cortex-A55.
> > > > > > > >
> > > > > > > > This patch is in preparation to disable WDT CH2 from the RZ/G2L
> > > > > > > > (alike
> > > > > > > > SoCs) DTS/I by default.
> > > > > > > >
> > > > > > > > Reported-by: Biju Das <biju.das.jz@...renesas.com>
> > > > > > > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> >
> > I got confirmation that that using WDT2 from CA55 is prohibited.
> > WDT2 is only for CM33.
> >
> > With CPG register, we can select whether CM33 to trigger CM33 cpu reset, or trigger system reset
> > when WDT2 overflows.
> >
> > If WDT2 is used by CA55, it may result in unexpected behaviour.
> >
> Thanks.
>
> > So we may need to take WDT2 entries from binding + dtsi + clock table??
> >
> > Or
> >
> > Added it to critical clock list, to avoid changes in binding + dtsi + clock table
> > at the expense of turning on the WDT2 clk unnecessarily.

... plus still risking to interfere with the CM33.

> I'm in favour of option#1 except that we keep WDT2 entries in binding.

Agreed (bindings are append-only).

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