linux-kernel - Re: [PATCH 2/10] clk: sunxi-ng: nkm: Deal with fixed post dividers

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Date:   Sun, 13 Nov 2016 11:49:30 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Chen-Yu Tsai <wens@...e.org>
Cc:     Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Mike Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>
Subject: Re: [PATCH 2/10] clk: sunxi-ng: nkm: Deal with fixed post dividers

On Sun, Nov 13, 2016 at 11:48 AM, Chen-Yu Tsai <wens@...e.org> wrote:
> On Wed, Nov 9, 2016 at 1:23 AM, Maxime Ripard
> <maxime.ripard@...e-electrons.com> wrote:
>
> It'd be better if you mentioned what clock needs this.
>
>> Signed-off-by: Maxime Ripard <maxime.ripard@...e-electrons.com>
>> ---
>>  drivers/clk/sunxi-ng/ccu_nkm.c | 17 ++++++++++++++---
>>  drivers/clk/sunxi-ng/ccu_nkm.h |  2 ++
>>  2 files changed, 16 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/clk/sunxi-ng/ccu_nkm.c b/drivers/clk/sunxi-ng/ccu_nkm.c
>> index 9b840a47a94d..fd3c6a9d987c 100644
>> --- a/drivers/clk/sunxi-ng/ccu_nkm.c
>> +++ b/drivers/clk/sunxi-ng/ccu_nkm.c
>> @@ -75,7 +75,7 @@ static unsigned long ccu_nkm_recalc_rate(struct clk_hw *hw,
>>                                         unsigned long parent_rate)
>>  {
>>         struct ccu_nkm *nkm = hw_to_ccu_nkm(hw);
>> -       unsigned long n, m, k;
>> +       unsigned long rate, n, m, k;
>>         u32 reg;
>>
>>         reg = readl(nkm->common.base + nkm->common.reg);
>> @@ -89,7 +89,11 @@ static unsigned long ccu_nkm_recalc_rate(struct clk_hw *hw,
>>         m = reg >> nkm->m.shift;
>>         m &= (1 << nkm->m.width) - 1;
>>
>> -       return parent_rate * (n + 1) * (k + 1) / (m + 1);
>> +       rate = parent_rate * (n + 1) * (k + 1) / (m + 1);
>> +       if (nkm->common.features & CCU_FEATURE_FIXED_POSTDIV)
>> +               rate /= nkm->fixed_post_div;
>> +
>> +       return rate;
>>  }
>>
>>  static unsigned long ccu_nkm_round_rate(struct ccu_mux_internal *mux,
>> @@ -100,6 +104,9 @@ static unsigned long ccu_nkm_round_rate(struct ccu_mux_internal *mux,
>>         struct ccu_nkm *nkm = data;
>>         struct _ccu_nkm _nkm;
>>
>> +       if (nkm->common.features & CCU_FEATURE_FIXED_POSTDIV)
>> +               rate *= nkm->fixed_post_div;
>> +
>>         _nkm.min_n = nkm->n.min;
>>         _nkm.max_n = 1 << nkm->n.width;
>>         _nkm.min_k = nkm->k.min;
>> @@ -109,7 +116,11 @@ static unsigned long ccu_nkm_round_rate(struct ccu_mux_internal *mux,
>>
>>         ccu_nkm_find_best(parent_rate, rate, &_nkm);
>>
>> -       return parent_rate * _nkm.n * _nkm.k / _nkm.m;
>> +       rate = parent_rate * _nkm.n * _nkm.k / _nkm.m;
>> +       if (nkm->common.features & CCU_FEATURE_FIXED_POSTDIV)
>> +               rate = rate / nkm->fixed_post_div;
>> +
>> +       return rate;
>>  }
>>
>
> You also need to handle this in the set_rate callback. You might need
> to read back
> the parent index value to determine if the post divider applies, as
> this clock supports
> a mux. Or don't support mux + post-div, and leave a TODO note.

Was thinking pre-dividers... sorry. Please ignore the second parent
index part.

ChenYu

>
> ChenYu
>
>>  static int ccu_nkm_determine_rate(struct clk_hw *hw,
>> diff --git a/drivers/clk/sunxi-ng/ccu_nkm.h b/drivers/clk/sunxi-ng/ccu_nkm.h
>> index 34580894f4d1..0f1dbca25719 100644
>> --- a/drivers/clk/sunxi-ng/ccu_nkm.h
>> +++ b/drivers/clk/sunxi-ng/ccu_nkm.h
>> @@ -32,6 +32,8 @@ struct ccu_nkm {
>>         struct ccu_mult_internal        n;
>>         struct ccu_mult_internal        k;
>>         struct ccu_div_internal         m;
>> +
>> +       unsigned int            fixed_post_div;
>>         struct ccu_mux_internal mux;
>>
>>         struct ccu_common       common;
>> --
>> git-series 0.8.11