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From:   Biju Das <biju.das.jz@bp.renesas.com>
To:     "Lad, Prabhakar" <prabhakar.csengg@gmail.com>
CC:     Geert Uytterhoeven <geert@linux-m68k.org>,
        Magnus Damm <magnus.damm@gmail.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        "linux-renesas-soc@vger.kernel.org" 
        <linux-renesas-soc@vger.kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com>
Subject: RE: [PATCH] arm64: dts: renesas: rzg2ul-smarc-som: Drop enabling wdt2
Thread-Topic: [PATCH] arm64: dts: renesas: rzg2ul-smarc-som: Drop enabling
 wdt2
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Date:   Mon, 19 Sep 2022 11:10:05 +0000
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Hi Prabhakar,

Mahadev Lad <prabhakar.mahadev-
> lad.rj@bp.renesas.com>
> Subject: Re: [PATCH] arm64: dts: renesas: rzg2ul-smarc-som: Drop
> enabling wdt2
>=20
> On Mon, Sep 19, 2022 at 11:55 AM Biju Das <biju.das.jz@bp.renesas.com>
> wrote:
> >
> >
> >
> > > -----Original Message-----
> > > From: Lad, Prabhakar <prabhakar.csengg@gmail.com>
> > > Sent: 19 September 2022 11:44
> > > To: Biju Das <biju.das.jz@bp.renesas.com>
> > > Cc: Geert Uytterhoeven <geert@linux-m68k.org>; Magnus Damm
> > > <magnus.damm@gmail.com>; Rob Herring <robh+dt@kernel.org>;
> Krzysztof
> > > Kozlowski <krzysztof.kozlowski+dt@linaro.org>; linux-renesas-
> > > soc@vger.kernel.org; devicetree@vger.kernel.org; linux-
> > > kernel@vger.kernel.org; Prabhakar Mahadev Lad <prabhakar.mahadev-
> > > lad.rj@bp.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@bp.renesas.com>
> > > wrote:
> > > >
> > > > Hi Geert,
> > > >
> > > > Prabhakar Mahadev Lad <prabhakar.mahadev-
> > > > > lad.rj@bp.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@bp.renesas.com>
> > > > > wrote:
> > > > > > > On Sun, Sep 18, 2022 at 10:04 AM Geert Uytterhoeven
> > > > > > > <geert@linux- m68k.org> wrote:
> > > > > > > > On Wed, Sep 14, 2022 at 3:43 PM Prabhakar
> > > > > > > <prabhakar.csengg@gmail.com> wrote:
> > > > > > > > > From: Lad Prabhakar
> > > > > > > > > <prabhakar.mahadev-lad.rj@bp.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).
>=20
> Or is it that I am missing something?

It all depends upon whether remove unused clocks turn off WDT2 clock during
late boot process.=20

I guess, since we have wdt2 entries in clock table, it will turn off WDT cl=
ock,
since you have disable it from DT( it becomes unused).

By adding critical clocks, it won't turn off the WDT clock.

Cheers,
Biju

>=20
> [1]
> https://jpn01.safelinks.protection.outlook.com/?url=3Dhttps%3A%2F%2Fgit.
> kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Fnext%2Flinux-
> next.git%2Fcommit%2F%3Fh%3Dnext-
> 20220919%26id%3D31989ece707adc453eb9f4f019fdac118f8fee72&amp;data=3D05%7
> C01%7Cbiju.das.jz%40bp.renesas.com%7C55f37d25d74646611de908da9a2ecfac%
> 7C53d82571da1947e49cb4625a166a4a2a%7C0%7C0%7C637991823087385873%7CUnkn
> own%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwi
> LCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=3DhP2u5NwutD8AhhrOrY6dPvlWW8PkB
> g3skyTMXBJQaWc%3D&amp;reserved=3D0
>=20
> 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