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From:   "Lad, Prabhakar" <prabhakar.csengg@gmail.com>
Date:   Wed, 5 Oct 2022 13:56:22 +0100
Message-ID: <CA+V-a8uNhM92ezEX3iCcP2zp3Er9EPDy1Z-4L3gQfe=xU8O1bw@mail.gmail.com>
Subject: Re: [PATCH] clk: renesas: r9a07g044: Add WDT2 clocks to critical list
To:     Biju Das <biju.das.jz@bp.renesas.com>
Cc:     Geert Uytterhoeven <geert+renesas@glider.be>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        "linux-renesas-soc@vger.kernel.org" 
        <linux-renesas-soc@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi Biju,

On Wed, Oct 5, 2022 at 9:27 AM Biju Das <biju.das.jz@bp.renesas.com> wrote:
>
> Hi Geert and Prabhakar,
>
> > Subject: RE: [PATCH] clk: renesas: r9a07g044: Add WDT2 clocks to
> > critical list
> >
> > Hi Prabhakar,
> >
> > > Subject: Re: [PATCH] clk: renesas: r9a07g044: Add WDT2 clocks to
> > > critical list
> > >
> > > Hi Biju,
> > >
> > > On Mon, Sep 19, 2022 at 2:52 PM Biju Das
> > <biju.das.jz@bp.renesas.com>
> > > wrote:
> > > >
> > > > Hi Prabhakar,
> > > >
> > > > > Subject: Re: [PATCH] clk: renesas: r9a07g044: Add WDT2 clocks to
> > > > > critical list
> > > > >
> > > > > Hi Biju,
> > > > >
> > > > > On Mon, Sep 19, 2022 at 2:35 PM Biju Das
> > > > > <biju.das.jz@bp.renesas.com>
> > > > > wrote:
> > > > > >
> > > > > > Hi Prabhakar,
> > > > > >
> > > > > > > Subject: [PATCH] clk: renesas: r9a07g044: Add WDT2 clocks to
> > > > > > > critical list
> > > > > > >
> > > > > > > From: Lad Prabhakar <prabhakar.mahadev-
> > lad.rj@bp.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@bp.renesas.com>
> > > > > > > Signed-off-by: Lad Prabhakar
> > > > > > > <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > > > > > > ---
> > > > > > >  drivers/clk/renesas/r9a07g044-cpg.c | 2 ++
> > > > > > >  1 file changed, 2 insertions(+)
> > > > > > >
> > > > > > > diff --git a/drivers/clk/renesas/r9a07g044-cpg.c
> > > > > > > b/drivers/clk/renesas/r9a07g044-cpg.c
> > > > > > > index 02a4fc41bb6e..cf9b1bd73792 100644
> > > > > > > --- a/drivers/clk/renesas/r9a07g044-cpg.c
> > > > > > > +++ b/drivers/clk/renesas/r9a07g044-cpg.c
> > > > > > > @@ -412,6 +412,8 @@ static const unsigned int
> > > > > > > r9a07g044_crit_mod_clks[] __initconst = {
> > > > > > >       MOD_CLK_BASE + R9A07G044_GIC600_GICCLK,
> > > > > > >       MOD_CLK_BASE + R9A07G044_IA55_CLK,
> > > > > > >       MOD_CLK_BASE + R9A07G044_DMAC_ACLK,
> > > > > > > +     MOD_CLK_BASE + R9A07G044_WDT2_PCLK,
> > > > > > > +     MOD_CLK_BASE + R9A07G044_WDT2_CLK,
> > > > > >
> > > > > > Do we need to turn on this clock unnecessarily?
> > > > > >
> > > > > No, this is in preparation to disable WDT2 by default from
> > > RZ/G2L{C}
> > > > > DTS/I.
> > > >
> > > > But that will make WDT2 device is not enabled, but unnecessarily
> > the
> > > clk is on.
> > > >
> > > Agreed the clocks will be ON, but didnt we agree earlier for
> > > r9a07g043-cpg.c?
> >
> > Yep, still we have a chance to conclude, whether we need to make this
> > clk always on, if it is not enabled and there is no use case for wdt2
> > controlling from CA-55??
> >
>
> 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.
>
I'm in favour of option#1 except that we keep WDT2 entries in binding.
Said that I'll leave Geert to decide on this.

Cheers,
Prabhakar