Subject: Re: [PATCH v2 01/12] clk: add new flag CLK_ROUNDING_NOOP

From: Brian Masney <[email-masked]>
Date: Wed, 29 Apr 2026 09:55:39 -0400

On Tue, Apr 28, 2026 at 07:15:36PM -0700, Stephen Boyd wrote:
> Quoting Brian Masney (2026-03-09 07:38:40)
> > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> > index fd418dc988b1c60c49e3ac9c0c44aa132dd5da28..1187e5b1dbc123d2d2c1f43690d7dcf75a7c4ac3 100644
> > --- a/drivers/clk/clk.c
> > +++ b/drivers/clk/clk.c
> > @@ -1673,7 +1690,7 @@ EXPORT_SYMBOL_GPL(clk_hw_forward_rate_request);
> >  
> >  static bool clk_core_can_round(struct clk_core * const core)
> >  {
> > -       return core->ops->determine_rate;
> > +       return core->ops->determine_rate || clk_is_rounding_noop(core);
> >  }
> >  
> >  static int clk_core_round_rate_nolock(struct clk_core *core,
> > @@ -3528,6 +3545,7 @@ static const struct {
> >         ENTRY(CLK_IS_CRITICAL),
> >         ENTRY(CLK_OPS_PARENT_ENABLE),
> >         ENTRY(CLK_DUTY_CYCLE_PARENT),
> > +       ENTRY(CLK_ROUNDING_NOOP),
> >  #undef ENTRY
> >  };
> >  
> > @@ -3906,13 +3924,19 @@ static int __clk_core_init(struct clk_core *core)
> >  
> >         /* check that clk_ops are sane.  See Documentation/driver-api/clk.rst */
> >         if (core->ops->set_rate && !core->ops->determine_rate &&
> > -             core->ops->recalc_rate) {
> > +             core->ops->recalc_rate && !clk_is_rounding_noop(core)) {
> >                 pr_err("%s: %s must implement .determine_rate in addition to .recalc_rate\n",
> >                        __func__, core->name);
> >                 ret = -EINVAL;
> >                 goto out;
> >         }
> >  
> > +       if (clk_is_rounding_noop(core) && core->ops->determine_rate) {
> > +               pr_err("%s: %s cannot implement both .determine_rate and CLK_ROUNDING_NOOP\n",
> > +                      __func__, core->name);
> > +               goto out;
> > +       }
> > +
> 
> This hunk has me irked. I'd rather we export some function like
> clk_determine_rate_noop() that just returns 0 instead of adding another
> flag. The chance that someone can get it wrong goes down and you can
> naturally grep for any clks that are using determine_rate() without
> having to also include this flag in the grep. It makes it easier to
> reason about as well because we can have code that just checks for
> determine_rate presence instead of both (i.e. clk_core_can_round() isn't
> changed). Plus a clk_ops structure is more self-contained because it
> doesn't rely on the clk flags to go with it.

I also like the clk_determine_rate_noop() approach much better as well.
I'll send a new version.

Thanks,
Brian