linux-kernel - Re: [PATCH v4 03/26] clk: sunxi-ng: Add check for maximum rate to NKM PLLs

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Date:   Tue, 20 Nov 2018 11:55:57 +0100
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Jagan Teki <jagan@...rulasolutions.com>
Cc:     Chen-Yu Tsai <wens@...e.org>, Icenowy Zheng <icenowy@...c.io>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Vasily Khoruzhick <anarsoul@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        David Airlie <airlied@...ux.ie>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        Michael Trimarchi <michael@...rulasolutions.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-sunxi@...glegroups.com, linux-amarula@...rulasolutions.com
Subject: Re: [PATCH v4 03/26] clk: sunxi-ng: Add check for maximum rate to
 NKM PLLs

On Thu, Nov 15, 2018 at 08:51:04PM +0530, Jagan Teki wrote:
> > >  drivers/clk/sunxi-ng/ccu_nkm.c | 3 +++
> > >  drivers/clk/sunxi-ng/ccu_nkm.h | 1 +
> > >  2 files changed, 4 insertions(+)
> > >
> > > diff --git a/drivers/clk/sunxi-ng/ccu_nkm.c b/drivers/clk/sunxi-ng/ccu_nkm.c
> > > index 6b5ad990f802..b8b66cdd30bf 100644
> > > --- a/drivers/clk/sunxi-ng/ccu_nkm.c
> > > +++ b/drivers/clk/sunxi-ng/ccu_nkm.c
> > > @@ -128,6 +128,9 @@ static unsigned long ccu_nkm_round_rate(struct ccu_mux_internal *mux,
> > >       if (rate < nkm->min_rate)
> > >               return nkm->min_rate;
> > >
> > > +     if (nkm->max_rate && rate > nkm->max_rate)
> > > +             return nkm->max_rate;
> > > +
> >
> > I would expect the test to be the same for the minimum and maximum cases.
> 
> I don't have proper use-case for max rate test, I do verify by using
> higher the rate on dclock, but nor sure.  May be I can skip the
> max_rate patch?

So you're sending more patches that you haven't really tested?
Why are you sending them then?

> Apart from this, any idea about this issue where SUN4I_TCON0_DCLK_REG
> will only work with div upto 6 on A64 DSI panels[1], did you find the
> same issue on A33?

IIRC my panel was falling into the case where the divider was 4, so
I've not fallen into that case.

> With parent rate 330MHz, the resulting tcon divider for 30MHz [2]
> clock is 11 and for the same for 55MHz [3] clock is 6.

I'm not sure what the question is?

Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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