linux-kernel - Re: [PATCH] arm64: dts: renesas: rzg2ul-smarc-som: Drop enabling wdt2

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Message-ID: <CA+V-a8sXfRQAMDGhF4JnK-Ucmb6G502oxt8L=wYZP2Vb3bd3jA@mail.gmail.com>
Date:   Mon, 19 Sep 2022 12:04:36 +0100
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Biju Das <biju.das.jz@...renesas.com>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Magnus Damm <magnus.damm@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...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] arm64: dts: renesas: rzg2ul-smarc-som: Drop enabling wdt2

On Mon, Sep 19, 2022 at 11:55 AM Biju Das <biju.das.jz@...renesas.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Lad, Prabhakar <prabhakar.csengg@...il.com>
> > Sent: 19 September 2022 11:44
> > To: Biju Das <biju.das.jz@...renesas.com>
> > Cc: Geert Uytterhoeven <geert@...ux-m68k.org>; Magnus Damm
> > <magnus.damm@...il.com>; Rob Herring <robh+dt@...nel.org>; Krzysztof
> > Kozlowski <krzysztof.kozlowski+dt@...aro.org>; linux-renesas-
> > soc@...r.kernel.org; devicetree@...r.kernel.org; linux-
> > kernel@...r.kernel.org; Prabhakar Mahadev Lad <prabhakar.mahadev-
> > lad.rj@...renesas.com>
> > Subject: Re: [PATCH] arm64: dts: renesas: rzg2ul-smarc-som: Drop
> > enabling wdt2
> >
> > On Mon, Sep 19, 2022 at 11:15 AM Biju Das <biju.das.jz@...renesas.com>
> > wrote:
> > >
> > > Hi Geert,
> > >
> > > Prabhakar Mahadev Lad <prabhakar.mahadev-
> > > > lad.rj@...renesas.com>
> > > > Subject: Re: [PATCH] arm64: dts: renesas: rzg2ul-smarc-som: Drop
> > > > enabling wdt2
> > > >
> > > > Hi Biju,
> > > >
> > > > On Mon, Sep 19, 2022 at 12:06 PM Biju Das
> > > > <biju.das.jz@...renesas.com>
> > > > wrote:
> > > > > > On Sun, Sep 18, 2022 at 10:04 AM Geert Uytterhoeven
> > > > > > <geert@...ux- m68k.org> wrote:
> > > > > > > On Wed, Sep 14, 2022 at 3:43 PM Prabhakar
> > > > > > <prabhakar.csengg@...il.com> wrote:
> > > > > > > > From: Lad Prabhakar
> > > > > > > > <prabhakar.mahadev-lad.rj@...renesas.com>
> > > > > > > >
> > > > > > > > WDT CH2 is specifically to check the operation of Cortex-
> > M33
> > > > CPU
> > > > > > so
> > > > > > > > don't enable WDT2 by default.
> > > > > > > >
> > > > > > For consistency I'll drop enabling WDT2 from the RZ/G2L{C}
> > too.
> > > > >
> > > > > Does remove unused clocks turn off WDT2 clock during late init??
> > > > >
> > > > > If that is the case, we should remove entries from clock table
> > as
> > > > well?
> > > >
> > > > Or add it to *_crit_mod_clks[]?
> > > >
> > > > Note that drivers/clk/renesas/r9a07g043-cpg.c creates wdt2 clocks
> > > > and resets, so that should probably be moved inside the #ifdef
> > > > CONFIG_ARM64 section.
> > >
> > Yes we dont want it to be listed on RZ/Five.
>
> OK, So this patch [1] will break existing RZ/G2UL till we have clk changes suggested by Geert.
>
No it won't, patch [1] just disables enabling wdt2 on A55. Whereas
Geert is suggesting adding wdt2 clk R9A07G043_WDT2_PCLK (and also
R9A07G043_WDT2_CLK?)  to crit_mod_clks so that we dont disable them in
A55 (currently we dont have any scenario where M33 is up with WDT2 and
patch [1] is breaking it). Also Geert's other suggestion was to add
the WDT2 clocks under ARM64 as we dont want them to be visible under
RZ/Five (where wdt2 is not present).

Or is it that I am missing something?

[1] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?h=next-20220919&id=31989ece707adc453eb9f4f019fdac118f8fee72

Cheers,
Prabhakar
>
> >
> > > Yes, both will do, I guess otherwise WDT enabled by Cortex-M33 will
> > be
> > > disabled by
> > > CORTEX-A55 during boot.
> > >
> > Agreed.
> >
> > Cheers,
> > Prabhakar