Re: [linux-sunxi] Re: [PATCH v6 1/6] clk: sunxi-ng: div: Add support for fixed post-divider

[icenowy]

å 2017-08-12 12:13ïChen-Yu Tsai åéï
> On Sat, Aug 12, 2017 at 11:07 AM,  <icenowy@xxxxxxx> wrote:
> > å 2017-07-17 16:52ïMaxime Ripard åéï
> > > On Fri, Jul 14, 2017 at 05:49:23PM +0300, Priit Laes wrote:
> > > > SATA clock on sun4i/sun7i is of type (parent) / M / 6 where
> > > > 6 is fixed post-divider.
> > > >
> > > > Signed-off-by: Priit Laes <plaes@xxxxxxxxx>
> > > > ---
> > > >  drivers/clk/sunxi-ng/ccu_div.c | 15 +++++++++++++--
> > > >  drivers/clk/sunxi-ng/ccu_div.h |  3 ++-
> > > >  2 files changed, 15 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/drivers/clk/sunxi-ng/ccu_div.c
> > > > b/drivers/clk/sunxi-ng/ccu_div.c
> > > > index c0e5c10..744502a 100644
> > > > --- a/drivers/clk/sunxi-ng/ccu_div.c
> > > > +++ b/drivers/clk/sunxi-ng/ccu_div.c
> > > > @@ -21,6 +21,9 @@ static unsigned long ccu_div_round_rate(struct
> > > > ccu_mux_internal *mux,
> > > >  {
> > > >         struct ccu_div *cd = data;
> > > >
> > > > +       if (cd->common.features & CCU_FEATURE_FIXED_POSTDIV)
> > > > +               rate *= cd->fixed_post_div;
> > > > +
> > > >         return divider_round_rate_parent(&cd->common.hw, parent,
> > > >                                          rate, parent_rate,
> > > >                                          cd->div.table, 
> > > > cd->div.width,
> > >
> > >
> > >
> > > You still haven't addressed the biggest issue with this patch, see:
> > > https://patchwork.kernel.org/patch/9825565/
> >
> >
> > I think he has already did the changes suggested in the review.
>
> Nope. Only half of it is fixed. First you "unapply" the post-divider,
> i.e. multiply the rate by the divider. Then you pass it to
> divider_round_rate_parent. You still have to reapply the divider
> to the result. This last part is missing. This means the clock
> rate returned by ccu_div_round_rate is going to be off.
>
> Instead the return statement should be
>
>     return divider_round_rate_parent(...) / cd->fixed_post_div

Oh, got it by reading other CCU clock types that has fixed postdiv.

Thanks!

> ChenYu
>
> > (P.S. during developing R40 CCU driver I found that pll-periph0-sata
> > also needs this patch, so I'm rechecking it)
> >
> > > Maxime
> > >
> > > _______________________________________________
> > > linux-arm-kernel mailing list
> > > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> >
> >
> > --
> > You received this message because you are subscribed to the Google 
> > Groups
> > "linux-sunxi" group.
> > To unsubscribe from this group and stop receiving emails from it, send 
> > an
> > email to linux-sunxi+unsubscribe@xxxxxxxxxxxxxxxxx
> > For more options, visit https://groups.google.com/d/optout.
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel