Hi Simon,
On Mon, Sep 2, 2019 at 10:31 AM Simon Horman <horms@xxxxxxxxxxxx> wrote:
> On Fri, Aug 30, 2019 at 10:43:01AM +0200, Geert Uytterhoeven wrote:
> > On Tue, Jun 18, 2019 at 1:09 PM Simon Horman <horms@xxxxxxxxxxxx> wrote:
> > > On Mon, Jun 17, 2019 at 02:52:34PM +0200, Geert Uytterhoeven wrote:
> > > > 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. Hence switch the Z clock on R-Car Gen2 from the old
> > > > .round_rate() callback to the newer .determine_rate() callback, which
> > > > does not suffer from this limitation.
> > > >
> > > > This includes implementing range checking.
> > > >
> > > > Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> >
> > > > --- a/drivers/clk/renesas/clk-rcar-gen2.c
> > > > +++ b/drivers/clk/renesas/clk-rcar-gen2.c
> > > > @@ -66,19 +66,22 @@ static unsigned long cpg_z_clk_recalc_rate(struct clk_hw *hw,
> > > > return div_u64((u64)parent_rate * mult, 32);
> > > > }
> > > >
> > > > -static long cpg_z_clk_round_rate(struct clk_hw *hw, unsigned long rate,
> > > > - unsigned long *parent_rate)
> > > > +static int cpg_z_clk_determine_rate(struct clk_hw *hw,
> > > > + struct clk_rate_request *req)
> > > > {
> > > > - unsigned long prate = *parent_rate;
> > > > - unsigned int mult;
> > > > + unsigned long prate = req->best_parent_rate;
> > > > + unsigned int min_mult, max_mult, mult;
> > > >
> > > > - if (!prate)
> > > > - prate = 1;
> > > > + min_mult = max(div_u64(req->min_rate * 32ULL, prate), 1ULL);
> > > > + max_mult = min(div_u64(req->max_rate * 32ULL, prate), 32ULL);
> > >
> > > nit: the type of the second parameter doesn't look correct to me,
> > > div_u64 expects a u32 divisor.
> >
> > Yes, this should use div64_ul() instead.
>
> Ok, but in that case should the constants be "UL" instead of "UUL" ?
The first or the second? ;-)
The multiplication should always be calculated using 64-bit arithmetic,
hence the first ULL suffix.
The max() macro needs two parameters of the same type, and
div64_ul() returns u64, hence the second ULL suffix.
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
