RE: [PATCH v14 09/11] clk: realtek: Add RTD1625-CRT clock controller driver

[Jerome Brunet <jbrunet@baylibre.com>]

On mer. 23 sept. 2026 at 05:43, Yu-Chun Lin [林祐君] <eleanor.lin@realtek.com> wrote:

> Hi Jerome,
>
>> > +
>> > +static const char * const clk_gpu_parents[] = {"pll_gpu", "clk_sys"};
>> > +static RTK_CLK_REGMAP_MUX(clk_gpu, clk_gpu_parents,
>> CLK_SET_RATE_PARENT | CLK_SET_RATE_NO_REPARENT,
>> > +                       0x28, 12, 0x1); static const char * const
>> > +clk_ve_parents[] = {"pll_vo", "clk_sysh", "pll_ve1", "pll_ve2"};
>> > +static RTK_CLK_REGMAP_MUX(clk_ve1, clk_ve_parents,
>> CLK_SET_RATE_PARENT | CLK_SET_RATE_NO_REPARENT,
>> > +                       0x4c, 0, 0x3); static
>> > +RTK_CLK_REGMAP_MUX(clk_ve2, clk_ve_parents, CLK_SET_RATE_PARENT |
>> CLK_SET_RATE_NO_REPARENT,
>> > +                       0x4c, 3, 0x3); static
>> > +RTK_CLK_REGMAP_MUX(clk_ve4, clk_ve_parents, CLK_SET_RATE_PARENT |
>> CLK_SET_RATE_NO_REPARENT,
>> > +                       0x4c, 6, 0x3); static
>> > +RTK_CLK_REGMAP_GATE_NO_PARENT(clk_en_misc, CLK_IS_CRITICAL, 0x50,
>> 0,
>> > +1); clk_en_pcie0, 0, 0x50, 2,
>> > +1); clk_en_gspi, 0, 0x50, 6, 1);
>> > +clk_en_iso_misc, 0, 0x50, 10,
>> > +1); clk_en_sds, 0, 0x50, 12, 1);
>> > +clk_en_hdmi, 0, 0x50, 14, 1);
>> 
>> This is a lot of clock with no parents which is a bit suspicious especially for
>> gates.
>> What is really feeding those ?
>> 
>
> In v15, we will do our best to reduce the number of gate clocks without a parent.
>
> However, after discussing with our colleague, we confirmed that for some of
> these NO_PARENT gate clocks, their actual upstream clocks (like PLLs and
> Muxes) are located in separate, independent hardware subsystems. The registers
> controlling those upstream clocks are physically inaccessible from the Linux
> CPU domain.

Control and input are different things. It feels like your DT (binding)
description is not complete as it stands which will eventually be a problem.

A clock with no input is something that does generate the clock by
itself, like an osciallator. Pretending it has no parent because you
don't know how describe it yet is wrong.

>
> Best Regards,
> Yu-Chun

-- 
Jerome