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

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Date:   Mon, 19 Sep 2022 14:38:44 +0000
From:   Biju Das <biju.das.jz@...renesas.com>
To:     "Lad, Prabhakar" <prabhakar.csengg@...il.com>
CC:     Geert Uytterhoeven <geert+renesas@...der.be>,
        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,

> 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@...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@...renesas.com>
> > > wrote:
> > > >
> > > > Hi Prabhakar,
> > > >
> > > > > Subject: [PATCH] clk: renesas: r9a07g044: Add WDT2 clocks to
> > > > > critical list
> > > > >
> > > > > 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>
> > > > > ---
> > > > >  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??

Cheers,
Biju

> 
> > Not sure, If we have any use case for wdt2 controlling from CA-55??
> > If there is no use case, why can't we remove it from SoC dtsi and
> > clock tables, that why we don't unnecessarily use this clock
> anymore??
> >
> I dont have a clear use case of using WDT ch2 when trying to use it
> from CA-55 either.
> 
> Cheers,
> Prabhakar