linux-kernel - Re: [PATCH v4 4/7] rtc: ac100: Add clk output support

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Date:	Fri, 22 Jul 2016 09:22:25 +0800
From:	Chen-Yu Tsai <wens@...e.org>
To:	Michael Turquette <mturquette@...libre.com>
Cc:	Chen-Yu Tsai <wens@...e.org>, Lee Jones <lee.jones@...aro.org>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	rtc-linux@...glegroups.com, linux-clk <linux-clk@...r.kernel.org>,
	devicetree <devicetree@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 4/7] rtc: ac100: Add clk output support

On Fri, Jul 22, 2016 at 8:24 AM, Michael Turquette
<mturquette@...libre.com> wrote:
> Quoting Chen-Yu Tsai (2016-07-13 20:34:34)
>> On Sat, Jul 9, 2016 at 2:36 AM, Michael Turquette
>> <mturquette@...libre.com> wrote:
>> > Quoting Chen-Yu Tsai (2016-06-30 08:58:48)
>> >> +static long ac100_clkout_round_rate(struct clk_hw *hw, unsigned long rate,
>> >> +                                   unsigned long prate)
>> >> +{
>> >> +       unsigned long best_rate = 0, tmp_rate, tmp_prate;
>> >> +       int i;
>> >> +
>> >> +       if (prate == AC100_RTC_32K_RATE)
>> >> +               return divider_round_rate(hw, rate, &prate, NULL,
>> >> +                                         AC100_CLKOUT_DIV_WIDTH,
>> >> +                                         CLK_DIVIDER_POWER_OF_TWO);
>> >> +
>> >> +       for (i = 0; ac100_clkout_prediv[i].div; i++) {
>> >> +               tmp_prate = DIV_ROUND_UP(prate, ac100_clkout_prediv[i].val);
>> >> +               tmp_rate = divider_round_rate(hw, rate, &tmp_prate, NULL,
>> >> +                                             AC100_CLKOUT_DIV_WIDTH,
>> >> +                                             CLK_DIVIDER_POWER_OF_TWO);
>> >> +
>> >> +               if (tmp_rate > rate)
>> >> +                       continue;
>> >> +               if (rate - tmp_rate < best_rate - tmp_rate)
>> >> +                       best_rate = tmp_rate;
>> >> +       }
>> >> +
>> >> +       return best_rate;
>> >> +}
>> >> +
>> >> +static int ac100_clkout_determine_rate(struct clk_hw *hw,
>> >> +                                      struct clk_rate_request *req)
>> >> +{
>> >> +       struct clk_hw *best_parent;
>> >> +       unsigned long best = 0;
>> >> +       int i, num_parents = clk_hw_get_num_parents(hw);
>> >> +
>> >> +       for (i = 0; i < num_parents; i++) {
>> >> +               struct clk_hw *parent = clk_hw_get_parent_by_index(hw, i);
>> >> +               unsigned long tmp, prate = clk_hw_get_rate(parent);
>> >> +
>> >> +               tmp = ac100_clkout_round_rate(hw, req->rate, prate);
>> >> +
>> >> +               if (tmp > req->rate)
>> >> +                       continue;
>> >> +               if (req->rate - tmp < req->rate - best) {
>> >> +                       best = tmp;
>> >> +                       best_parent = parent;
>> >> +               }
>> >> +       }
>> >> +
>> >> +       if (!best)
>> >> +               return -EINVAL;
>> >> +
>> >> +       req->best_parent_hw = best_parent;
>> >> +       req->best_parent_rate = best;
>> >> +       req->rate = best;
>> >> +
>> >> +       return 0;
>> >> +}
>> >
>> > You only need one of the two functions above. Keep the .determine_rate
>> > callback and drop .round_rate.
>>
>> Only .round_rate is set in the clk_ops. ac100_clkout_round_rate just
>> serves to split out some of the calculations done per parent.
>
> If you only use .round_rate, shouldn't you drop .determine_rate then?

Oops! I meant we only set .determine_rate. ac100_clkout_round_rate is
called in the per parent loop in .determine_rate.

ChenYu

>
> Regards,
> Mike
>
>>
>> > Otherwise the rest of the clk support looks great to me. Feel free to
>> > add:
>> >
>> > Reviewed-by: Michael Turquette <mturquette@...libre.com>
>>
>> Thanks!
>>
>> ChenYu