Re: [PATCH v2 0/8] clk: renesas: rcar-gen2/gen3: Switch to .determine_rate()

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Stephen,

On Wed, Sep 4, 2019 at 12:09 AM Stephen Boyd <sboyd@kernel.org> wrote:
> Quoting Geert Uytterhoeven (2019-08-30 06:45:07)
> > As the .round_rate() callback returns a long clock rate, it cannot
> > return clock rates that do not fit in signed long, but do fit in
> > unsigned long.  The newer .determine_rate() callback does not suffer
> > from this limitation.  In addition, .determine_rate() provides the
> > ability to specify a rate range.
> >
> > This patch series performs the customary preparatory cleanups, and
> > switches the Z (CPU) and SD clocks in the R-Car Gen2 and Gen3 clock
> > drivers from the .round_rate() to the .determine_rate() callback.
> > Note that the "div6" clock driver hasn't been converted yet, so div6
> > clocks still use .round_rate().
> >
> > Changes compared to v1[1]:
> >   - Add preparatory arithmetic division improvements
> >   - Split off cpg_sd_clock_calc_div() absorption and SD clock best rate
> >     calculation,
> >   - Use div_u64() for division by unsigned long,
> >
> > This has been tested on R-Car M2-W and various R-Car Gen3, and should
> > have no behavioral impact.
>
> From what I recall the rate range code is broken but I can't remember
> how. Anyway, I was just curious if you ran into any issues with that
> code.

I didn't ran into any issues.  But please note that in all tested cases, the
limits were 0 and ULONG_MAX anyway, so probably it didn't trigger the
broken cases in the rate range code.

So, is it good to have .determine_rate() support in individual clock drivers
now, or do you want me to postpone the last 3 patches of my series until the
rate range code is fixed?

Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

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