Re: [PATCH 2/2 v2] ARM: mach-shmobile: clock-sh7372: FSI parent

[Magnus Damm <magnus.damm@gmail.com>]

Hi Morimoto-san,

On Fri, Sep 24, 2010 at 4:33 PM, Kuninori Morimoto
<kuninori.morimoto.gx@renesas.com> wrote:
>> > +       /*
>> > +        * FSIACK is connected to AK4642,
>> > +        * and the rate is depend on playing sound rate.
>> > +        * So, set dummy rate (= 48k) here
>> > +        */
>> > +       ret = clk_set_rate(&sh7372_fsiack_clk, FSIACK_DUMMY_RATE);
>> > +       if (ret < 0) {
>> > +               pr_err("Cannot set FSIACK dummy rate: %d\n", ret);
>> > +               return ret;
>> > +       }
>> > +
>> > +       fsia_ick = clk_get(&fsi_device.dev, "icka");
>> > +       if (IS_ERR(fsia_ick)) {
>> > +               ret = PTR_ERR(fsia_ick);
>> > +               pr_err("Cannot get FSI ICK: %d\n", ret);
>> > +               return ret;
>> > +       }
>> > +
>> > +       ret = clk_set_parent(fsia_ick, &sh7372_fsiack_clk);
>> > +       if (ret < 0) {
>> > +               pr_err("Cannot set FSI-A parent: %d\n", ret);
>> > +               goto out;
>> > +       }
>> > +
>> > +       ret = clk_set_rate(fsia_ick, FSIACK_DUMMY_RATE);
>> > +       if (ret < 0)
>> > +               pr_err("Cannot set FSI-A rate: %d\n", ret);
>>
>> Is it really necessary to perform clk_set_rate() two times?
>
> Yes. both are needed.
>
> 1st dummy clk_set_rate is needed to ensure
> clk->rate of external pin (which is needed for 2nd clk_set_rate).
>
> 2nd clk_set_rate assure 1/1 clock divide for FSI-A.
> because default FSI-A division ratio is 1/64.

Ok, I understand and agree. I think your latest patch is ok.

Thanks for your help!

/ magnus