Re: [linux-sunxi] Re: [PATCH v2 02/15] clk: sunxi-ng: Add check for minimal rate to NKM PLLs

[Jagan Teki]

On 29/10/18 2:28 PM, Maxime Ripard wrote:
> On Thu, Oct 25, 2018 at 04:25:59PM +0530, Jagan Teki wrote:
> > On Wed, Oct 24, 2018 at 11:34 PM Maxime Ripard
> > <maxime.ripard@xxxxxxxxxxx> wrote:
> > > On Tue, Oct 23, 2018 at 09:20:22PM +0530, Jagan Teki wrote:
> > > > Some NKM PLLs doesn't work well when their output clock rate is set below
> > > > certain rate.
> > > >
> > > > So, add support for minimal rate for relevant PLLs.
> > > >
> > > > Signed-off-by: Jagan Teki <jagan@xxxxxxxxxxxxxxxxxxxx>
> > > > ---
> > > > Changes for v2:
> > > > - new patch
> > > >
> > > >   drivers/clk/sunxi-ng/ccu_nkm.c | 7 +++++++
> > > >   drivers/clk/sunxi-ng/ccu_nkm.h | 1 +
> > > >   2 files changed, 8 insertions(+)
> > > >
> > > > diff --git a/drivers/clk/sunxi-ng/ccu_nkm.c b/drivers/clk/sunxi-ng/ccu_nkm.c
> > > > index 841840e35e61..d17539dc88dd 100644
> > > > --- a/drivers/clk/sunxi-ng/ccu_nkm.c
> > > > +++ b/drivers/clk/sunxi-ng/ccu_nkm.c
> > > > @@ -125,6 +125,13 @@ static unsigned long ccu_nkm_round_rate(struct ccu_mux_internal *mux,
> > > >        if (nkm->common.features & CCU_FEATURE_FIXED_POSTDIV)
> > > >                rate *= nkm->fixed_post_div;
> > > >
> > > > +     if (rate < nkm->min_rate) {
> > > > +             rate = nkm->min_rate;
> > > > +             if (nkm->common.features & CCU_FEATURE_FIXED_POSTDIV)
> > > > +                     rate /= nkm->fixed_post_div;
> > >
> > > I'm not sure this is right. Is the post divider taken into account to
> > > calculate the minimum, or is the minimum on the rate before the fixed
> > > post divider.
> >
> > Since we are returning from here, we need to take care post div which
> > is actually doing at the end of round_rate.
>
> That's not my point though. Does the rate needs to be superior to min
> / post_div, or min?

ie what I'm trying to say, since it's common code min or max should / 
post_div and PLL_MIPI doesn't use any post_div.

We need to take care post_div though the current test (PLL_MIPI) in not 
used since it's common code. just like nkmp, nm etc.

> > > How did you test this?
> >
> > I've not used this on PLL_MIPI atleast, so I didn't test this.
>
> If you've never tested this, why are you adding that code?

Like above, it's common code. otherwise might effect.