linux-kernel - Re: [RFC PATCH 1/2] clk: renesas: rzg2l: Don't assume all CPG

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Date:   Wed, 28 Sep 2022 10:37:41 +0100
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Biju Das <biju.das.jz@...renesas.com>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [RFC PATCH 1/2] clk: renesas: rzg2l: Don't assume all CPG_MOD
 clocks support PM

Hi Biju,

On Wed, Sep 28, 2022 at 9:42 AM Biju Das <biju.das.jz@...renesas.com> wrote:
>
> > Subject: Re: [RFC PATCH 1/2] clk: renesas: rzg2l: Don't assume all
> > CPG_MOD clocks support PM
> >
> > Hi Biju,
> >
> > Thank you for the review.
> >
> > On Wed, Sep 28, 2022 at 8:02 AM Biju Das <biju.das.jz@...renesas.com>
> > wrote:
> > >
> > > Hi Prabhakar,
> > >
> > > > Subject: [RFC PATCH 1/2] clk: renesas: rzg2l: Don't assume all
> > > > CPG_MOD clocks support PM
> > > >
> > > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > > >
> > > > There are cases where not all CPG_MOD clocks should be assumed to
> > > > support PM. For example on the CRU block there is a particular
> > > > sequence that needs to be followed to initialize the CSI-2 D-PHY
> > in
> > > > which individual clocks need to be turned ON/OFF, due to which
> > > > Runtime PM support wasn't used by the CRU CSI-2 driver.
> > > >
> > > > This patch adds support to allow indicating if PM is supported by
> > > > the CPG_MOD clocks. A new macro is DEF_NO_PM() is added which sets
> > > > the no_pm flag in struct rzg2l_mod_clk and when the driver uses
> > > > Runtime PM support no_pm flag is checked to see if the clk needs
> > to
> > > > included as part of Runtime PM.
> > > >
> > > > CPG_MOD clocks with no_pm flag set need to be individually turned
> > > > ON/OFF depending on the requirement of the driver.
> > > >
> > > > Signed-off-by: Lad Prabhakar
> > > > <prabhakar.mahadev-lad.rj@...renesas.com>
> > > > ---
> > > >  drivers/clk/renesas/rzg2l-cpg.c | 35
> > > > +++++++++++++++++++++++++++++---
> > > > -  drivers/clk/renesas/rzg2l-cpg.h | 12 ++++++++---
> > > >  2 files changed, 40 insertions(+), 7 deletions(-)
> > > >
> > > > diff --git a/drivers/clk/renesas/rzg2l-cpg.c
> > > > b/drivers/clk/renesas/rzg2l-cpg.c index 3ff6ecd61756..d275324909e7
> > > > 100644
> > > > --- a/drivers/clk/renesas/rzg2l-cpg.c
> > > > +++ b/drivers/clk/renesas/rzg2l-cpg.c
> > > > @@ -114,6 +114,8 @@ struct rzg2l_cpg_priv {
> > > >       struct rzg2l_pll5_mux_dsi_div_param mux_dsi_div_params;  };
> > > >
> > > > +static struct rzg2l_cpg_priv *rzg2l_cpg_priv;
> > > > +
> > > >  static void rzg2l_cpg_del_clk_provider(void *data)  {
> > > >       of_clk_del_provider(data);
> > > > @@ -1223,18 +1225,42 @@ static int
> > > > rzg2l_cpg_reset_controller_register(struct rzg2l_cpg_priv *priv)
> > > >       return devm_reset_controller_register(priv->dev,
> > > > &priv->rcdev); }
> > > >
> > > > +static inline const struct rzg2l_mod_clk *rzg2l_get_mod_clk(const
> > > > +struct rzg2l_cpg_info *info, int id) {
> > > > +     unsigned int i;
> > > > +
> > > > +     id += info->num_total_core_clks;
> > > > +     for (i = 0; i < info->num_mod_clks; i++) {
> > > > +             if (info->mod_clks[i].id == id)
> > > > +                     return &info->mod_clks[i];
> > > > +     }
> > >
> > > May be as an optimization add ID and clk to a separate list and
> > > traverse that smaller list for DEF_NO_PM case.
> > >
> > > case CPG_MOD:
> > >         return rzg2l_cpg_is_pm_mod(clkspec->args[1]);
> > >
> > Are you suggesting adding no_pm_mod_clks and no_pm_mod_clks or
> > building an internal structure in struct rzg2l_cpg_priv while calling
> > rzg2l_cpg_register_mod_clk() for each mod clock?
>
> Later one. To have a smaller list of no_pm_mod_clks while registering as MOD
> Clocks and later add PM clocks will check for the matching clock ID and
> excludes it.
>
Agreed.

Cheers,
Prabhakar