linux-kernel - Re: [PATCH 1/4] clk: meson: mpll: add init callback and regs

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Date:   Tue, 26 Mar 2019 08:53:15 +0100
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Stephen Boyd <sboyd@...nel.org>,
        Neil Armstrong <narmstrong@...libre.com>
Cc:     linux-amlogic@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] clk: meson: mpll: add init callback and regs

On Mon, 2019-03-25 at 10:10 -0700, Stephen Boyd wrote:
> Quoting Jerome Brunet (2019-03-25 04:11:57)
> > @@ -138,6 +129,27 @@ static int mpll_set_rate(struct clk_hw *hw,
> >         return 0;
> >  }
> >  
> > +static void mpll_init(struct clk_hw *hw)
> > +{
> > +       struct clk_regmap *clk = to_clk_regmap(hw);
> > +       struct meson_clk_mpll_data *mpll = meson_clk_mpll_data(clk);
> > +
> > +       if (mpll->init_count)
> > +               regmap_multi_reg_write(clk->map, mpll->init_regs,
> > +                                      mpll->init_count);
> > +
> > +       /* Enable the fractional part */
> > +       meson_parm_write(clk->map, &mpll->sdm_en, 1);
> > +
> > +       /* Set additional fractional part enable if required */
> > +       if (MESON_PARM_APPLICABLE(&mpll->ssen))
> > +               meson_parm_write(clk->map, &mpll->ssen, 1);
> > +
> > +       /* Set the magic misc bit if required */
> > +       if (MESON_PARM_APPLICABLE(&mpll->misc))
> > +               meson_parm_write(clk->map, &mpll->misc, 1);
> > +}
> > +
> >  const struct clk_ops meson_clk_mpll_ro_ops = {
> >         .recalc_rate    = mpll_recalc_rate,
> >         .round_rate     = mpll_round_rate,
> > @@ -148,6 +160,7 @@ const struct clk_ops meson_clk_mpll_ops = {
> >         .recalc_rate    = mpll_recalc_rate,
> >         .round_rate     = mpll_round_rate,
> >         .set_rate       = mpll_set_rate,
> > +       .init           = mpll_init,
> 
> We actively discourage using init callbacks. Can you do this some other
> way?

Yes I'm aware of that but init it the right place to do this.
To be clear, this is not initializing the clock to some particular rate, the
rate is preserved.

It just applies the necessary settings that needs to be done only once to make
sure the clock is in working order and that the rate calculated is actually
accurate. 

> 
> >  };
> >  EXPORT_SYMBOL_GPL(meson_clk_mpll_ops);
> >