Re: [devicetree-org/dt-schema] schemas: introduce assigned-clock-sscs (PR #154)

[Peng Fan <peng.fan@oss.nxp.com>]

Hi Geert,

On Thu, Feb 13, 2025 at 11:16:31AM +0100, Geert Uytterhoeven wrote:
>CC devicetree
>
>On Fri, 24 Jan 2025 at 15:42, Krzysztof Kozlowski <krzk@kernel.org> wrote:
>> Just FYI, below is a foward of pull request for dtschema for bindings
>> adding spread spectrum to clocks. As Clock framework maintainers this
>> might be relevant to you.
>>
>> -------- Forwarded Message --------
>> Subject: [devicetree-org/dt-schema] schemas: introduce
>> assigned-clock-sscs (PR #154)
>> Date: Fri, 24 Jan 2025 04:31:30 -0800
>> From: Peng Fan <notifications@github.com>
>> Reply-To: devicetree-org/dt-schema
>> <reply+ACPRLI5YLXX27TFZX2P7NVOFT5USFEVBNHHKO4ZXHM@reply.github.com>
>> To: devicetree-org/dt-schema <dt-schema@noreply.github.com>
>> CC: Subscribed <subscribed@noreply.github.com>
>>
>> To support spread spectrum clock, introduce assigned-clock-sscs, it is
>> an uint32-matrix with format multiple elements of below
>> &lt;modfreq spreadpercentage modmethod&gt;, &lt;...&gt;
>> You can view, comment on, or merge this pull request online at:
>>
>>   https://github.com/devicetree-org/dt-schema/pull/154
>>
>> -- Commit Summary --
>>
>>   * schemas: introduce assigned-clock-sscs
>
>>   assigned-clock-sscs:
>>     $ref: /schemas/types.yaml#/definitions/uint32-matrix
>>     items:
>>       items:
>>         - description: The modulation frequency
>>         - description: The modulation depth in permyriad
>>         - description: The modulation method, down(2), up(1), center(0)
>
>Is there a way to explicitly disable it, if it was enabled by the
>firmware? See also my comment in "Re: [PATCH v2 1/4] clk: Introduce

The binding here is just to describe the parameter to configure
spread spectrum of a clk.

To disable spread spectrum, the clk_hw_set_spread_spectrum could be
used with enable as false or as you suggested using CLK_SSC_NONE_SPREAD?

>clk_hw_set_spread_spectrum".
>
>>           minimum: 0
>>           maximum: 2
>
>What's the meaning of these limits?

Modulation has three methods:
Down-spread modulation
Up-spread modulation
Center-spread modulation.

I use 2 for down, 1 for up, 0 for center here. So the limits:
min: 0, max: 2.

Thanks,
Peng

>
>[1] https://lore.kernel.org/CAMuHMdWn+sKiC1B4MF1vHwS2ArFYQXGzpYi2EcsyERPSCc9bvQ@mail.gmail.com
>
>Gr{oetje,eeting}s,
>
>                        Geert
>
>
>--
>Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
>In personal conversations with technical people, I call myself a hacker. But
>when I'm talking to journalists I just say "programmer" or something like that.
>                                -- Linus Torvalds
>