Re: [PATCH 04/11] ARM: shmobile: r8a7778: common clock framework CPG driver

[Ulrich Hecht <ulrich.hecht+renesas@gmail.com>]

On Thu, Jan 22, 2015 at 12:37 AM, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>> +     if (!strcmp(name, "extal")) {
>> +             return clk_register_fixed_rate(NULL, "extal", NULL,
>> +                     CLK_IS_ROOT, r8a7778_rates[cpg_mode_rates].extal_rate);
>
> As the external clock is an input to the CPG, shouldn't it be specified by a
> separate fixed-frequency clock DT node, and referenced by the CPG using the
> clocks attributes ? You could then remove the extal_rate field from the
> r8a7778_rates array above, and possibly rename the array to r8a7778_pll_mults
> or similar.
>

This is a translation of what the legacy clock driver does.  These
frequencies seem to be assumptions as to what input clocks would be
reasonable given the current mode bits.  If I interpret the schematics
correctly, the Bock-W board has a socketed oscillator, and the mode
bits are switchable, so it's up to the user to configure the board to
a sane setting.  To me, neither a fixed frequency nor this list of
educated guesses seems quite "right" under these circumstances...

CU
Uli