Re: [PATCH v4 11/21] riscv: Add Canaan Kendryte K210 clock driver

[Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>]

Hi Damien,

On Mon, Dec 7, 2020 at 4:52 AM Damien Le Moal <Damien.LeMoal@xxxxxxx> wrote:
> I prepared a v5 series addressing your comments (and other comments).
> I will post that later today after some more tests.

Thanks, already looking at k210-sysctl-v18...

> On Fri, 2020-12-04 at 22:19 -0800, Stephen Boyd wrote:
> > > --- /dev/null
> > > +++ b/drivers/clk/clk-k210.c

> > > +       in0_clk = of_clk_get(np, 0);
> > > +       if (IS_ERR(in0_clk)) {
> > > +               pr_warn("%pOFP: in0 oscillator not found\n", np);
> > > +               hws[K210_CLK_IN0] =
> > > +                       clk_hw_register_fixed_rate(NULL, "in0", NULL,
> > > +                                                  0, K210_IN0_RATE);
> > > +       } else {
> > > +               hws[K210_CLK_IN0] = __clk_get_hw(in0_clk);
> > > +       }
> > > +       if (IS_ERR(hws[K210_CLK_IN0])) {
> > > +               pr_err("%pOFP: failed to get base oscillator\n", np);
> > > +               goto err;
> > > +       }
> > > +
> > > +       in0 = clk_hw_get_name(hws[K210_CLK_IN0]);
> > > +       aclk_parents[0] = in0;
> > > +       pll_parents[0] = in0;
> > > +       mux_parents[0] = in0;
> >
> > Can we use the new way of specifying clk parents so that we don't have
> > to use __clk_get_hw(), of_clk_get(), and clk_hw_get_name()? Hopefully
> > the core can handl that all instead of this driver.
>
> I removed all this by adding:
>
> clock-output-names = "in0";
>
> to the DT fixed-rate oscillator clock node (and documented that too). Doing so,
> clk_hw_get_name(), __clk_get_hw() and of_clk_get() are not needed anymore and
> the parents clock names arrays do not need run-time update.

"clock-output-names" is deprecated for clocks with a single output:
the clock name will be taken from the node name.
However, relying on a clock name like this is fragile.
Instead, your driver should use the phandle from the clocks property,
using of_clk_get_by_name() or of_clk_get().

Stephen: I'm a bit puzzled, as you suggest _not_ using of_clk_get()?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds