linux-kernel - Re: [linux-sunxi] [PATCH v4 1/6] clk: sunxi-ng: div: Add support for fixed post-divider

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Date:   Mon, 26 Jun 2017 20:15:28 +1000
From:   Jonathan Liu <net147@...il.com>
To:     Priit Laes <plaes@...es.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Russell King <linux@...linux.org.uk>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        linux-clk@...r.kernel.org, devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [linux-sunxi] [PATCH v4 1/6] clk: sunxi-ng: div: Add support for
 fixed post-divider

Hi Priit,

On 26 June 2017 at 15:53, Priit Laes <plaes@...es.org> wrote:
> On Mon, Jun 26, 2017 at 08:05:16AM +1000, Jonathan Liu wrote:
>> Hi Priit,
>>
>> This is showing from clock rate of 171428572 in the output of "cat
>> /sys/kernel/debug/clk/clk_summary" for pll-periph-sata.
>> The clock rate should be 100000000 (100 MHz) when read from the hardware.
>
> This is what I see on Cubietruck. Can you check with sunxi-ccu-wip branch?
>
> $ cat /sys/kernel/debug/clk/clk_summary  |grep -i sata
>           pll-periph-sata                 1            1   100000000          0 0
>              sata                         1            1   100000000          0 0
>                 ahb-sata                  1            1   300000000          0 0
>

I checked with your sunxi-ccu-wip branch and I get the same results as
you. My branch seems out of date.

>>
>> On 26 June 2017 at 06:45, Priit Laes <plaes@...es.org> wrote:
>> > SATA clock on sun4i/sun7i is of type (parent) / M / 6 where
>> > 6 is fixed post-divider.
>> >
>> > Signed-off-by: Priit Laes <plaes@...es.org>
>> > ---
>> >  drivers/clk/sunxi-ng/ccu_div.c | 12 ++++++++++--
>> >  drivers/clk/sunxi-ng/ccu_div.h |  3 ++-
>> >  2 files changed, 12 insertions(+), 3 deletions(-)
>> >
>> > diff --git a/drivers/clk/sunxi-ng/ccu_div.c b/drivers/clk/sunxi-ng/ccu_div.c
>> > index c0e5c10..de30e15 100644
>> > --- a/drivers/clk/sunxi-ng/ccu_div.c
>> > +++ b/drivers/clk/sunxi-ng/ccu_div.c
>>
>> Missing handling of fixed_post_div in ccu_div_round_rate.
>> ccu_div_round_rate should multiply the rate by the postdiv before
>> looking up the divider using divider_get_val and divide val by postdiv
>> just before returning.
>>

Ignore the above comment, my branch is out of date.

>> > @@ -62,8 +62,13 @@ static unsigned long ccu_div_recalc_rate(struct clk_hw *hw,
>> >         parent_rate = ccu_mux_helper_apply_prediv(&cd->common, &cd->mux, -1,
>> >                                                   parent_rate);
>> >
>> > -       return divider_recalc_rate(hw, parent_rate, val, cd->div.table,
>> > -                                  cd->div.flags);
>> > +       val = divider_recalc_rate(hw, parent_rate, val, cd->div.table,
>> > +                                 cd->div.flags);
>> > +
>> > +       if (cd->common.features & CCU_FEATURE_FIXED_POSTDIV)
>> > +               val /= cd->fixed_post_div;
>> > +
>> > +       return val;
>> >  }
>> >
>> >  static int ccu_div_determine_rate(struct clk_hw *hw,
>>
>> > @@ -89,6 +94,9 @@ static int ccu_div_set_rate(struct clk_hw *hw, unsigned long rate,
>> >         val = divider_get_val(rate, parent_rate, cd->div.table, cd->div.width,
>> >                               cd->div.flags);
>> >
>> > +       if (cd->common.features & CCU_FEATURE_FIXED_POSTDIV)
>> > +               val *= cd->fixed_post_div;
>> > +
>> >         spin_lock_irqsave(cd->common.lock, flags);
>> >
>> >         reg = readl(cd->common.base + cd->common.reg);
>>
>> val here is the divider value that is stored in the clock register
>> field not the actual rate so this is incorrect. Instead the rate needs
>> to be multiplied by postdiv just before divider_get_val.
>
> OK, thanks, this one I wasn't really sure about.
>

Please do fix setting the rate though.

>>
>> > diff --git a/drivers/clk/sunxi-ng/ccu_div.h b/drivers/clk/sunxi-ng/ccu_div.h
>> > index 08d0744..f3a5028 100644
>> > --- a/drivers/clk/sunxi-ng/ccu_div.h
>> > +++ b/drivers/clk/sunxi-ng/ccu_div.h
>> > @@ -86,9 +86,10 @@ struct ccu_div_internal {
>> >  struct ccu_div {
>> >         u32                     enable;
>> >
>> > -       struct ccu_div_internal         div;
>> > +       struct ccu_div_internal div;
>> >         struct ccu_mux_internal mux;
>> >         struct ccu_common       common;
>> > +       unsigned int            fixed_post_div;
>> >  };
>> >
>> >  #define SUNXI_CCU_DIV_TABLE_WITH_GATE(_struct, _name, _parent, _reg,   \
>> > --
>> > git-series 0.9.1
>>
>> Thanks.
>>
>> Regards,
>> Jonathan

Regards,
Jonathan