linux-kernel - Re: [RFC PATCH 1/4] dt-bindings: clock: r9a07g043-cpg: Add Renesas RZ/Five CPG Clock and Reset Definitions

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Date:   Thu, 9 Jun 2022 10:56:20 +0100
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Biju Das <biju.das.jz@...renesas.com>,
        Phil Edworthy <phil.edworthy@...esas.com>
Subject: Re: [RFC PATCH 1/4] dt-bindings: clock: r9a07g043-cpg: Add Renesas
 RZ/Five CPG Clock and Reset Definitions

Hi Geert,

Sorry for the late reply.

On Thu, May 19, 2022 at 7:57 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> Hi Prabhakar,
>
> On Thu, May 19, 2022 at 7:45 AM Lad, Prabhakar
> <prabhakar.csengg@...il.com> wrote:
> > On Tue, May 10, 2022 at 3:02 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > > On Thu, May 5, 2022 at 9:32 PM Lad Prabhakar
> > > <prabhakar.mahadev-lad.rj@...renesas.com> wrote:
> > > > Renesas RZ/Five SoC has almost the same clock structure compared to the
> > > > Renesas RZ/G2UL SoC, re-use the r9a07g043-cpg.h header file and just
> > > > ammend the RZ/Five CPG clock and reset definitions.
> > >
> > > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > >
> > > > --- a/include/dt-bindings/clock/r9a07g043-cpg.h
> > > > +++ b/include/dt-bindings/clock/r9a07g043-cpg.h
> > > > @@ -108,6 +108,15 @@
> > > >  #define R9A07G043_ADC_ADCLK            76
> > > >  #define R9A07G043_ADC_PCLK             77
> > > >  #define R9A07G043_TSU_PCLK             78
> > > > +#define R9A07G043_NCEPLDM_DM_CLK       79      /* RZ/Five Only */
> > >
> > > While NCEPLDM_DM_CLK is listed in the clock list spreadsheet, its
> > > control bit is not documented.
> > >
> > > > +#define R9A07G043_NCEPLDM_ACLK         80      /* RZ/Five Only */
> > > > +#define R9A07G043_NCEPLDM_TCK          81      /* RZ/Five Only */
> > >
> > > While NCEPLDM_TCK is listed in the clock list spreadsheet, its
> > > control bit is not documented.
> > >
> > I have got the feedback for the above, NCEPLDM_DM_CLK and NCEPLDM_TCK
> > clocks cannot be stopped as a result there are no register bits for it
> > in the HW manual (clock spreadsheet will be updated). I will drop this
> > and send a v2 including your RB.
>
> The question is not if the clocks can be stopped or not, but if there
> is any need to refer to them from a DT node.
As per DT rule we have to add ;)

> What's the nature of the future update to the clock spreadsheet?
>
I have got confirmation from HW team, the UM and clock list will not be updated,

* NCEPLDM_DM_CLK, NCEPLDM_TCK and NCEPLDM_ACLK actually exist, and
should be listed on the clock list. Only NCEPLDM_ACLK has a mechanism
to stop.
* Therefore, only NCEPLDM_ACLK should appear on the Clock Control
register on the UM.

> Of course, if we don't add these clock definitions now, they can
> still be added later. DT binding definitions are append-only.
>
For now I will keep them.

Cheers,
Prabhakar