linux-kernel - Re: Re: [PATCH 1/6] dt-bindings: clocks: add binding for generic clock-generators

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Message-ID: <b3c450a94bcb4ad0bc5b3c7ee8712cb8.sboyd@kernel.org>
Date: Wed, 10 Jul 2024 16:56:46 -0700
From: Stephen Boyd <sboyd@...nel.org>
To: Heiko Stübner <heiko@...ech.de>, mturquette@...libre.com
Cc: robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org, quentin.schulz@...rry.de, linux-clk@...r.kernel.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-rockchip@...ts.infradead.org
Subject: Re:  Re: [PATCH 1/6] dt-bindings: clocks: add binding for generic clock-generators

Quoting Heiko Stübner (2024-07-10 01:02:57)
> Am Dienstag, 9. Juli 2024, 23:45:20 CEST schrieb Stephen Boyd:
> > Quoting Heiko Stuebner (2024-07-09 05:31:16)
> > > diff --git a/Documentation/devicetree/bindings/clock/clock-generator.yaml b/Documentation/devicetree/bindings/clock/clock-generator.yaml
> > > new file mode 100644
> > > index 0000000000000..f44e61e414e89
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/clock/clock-generator.yaml
> > > @@ -0,0 +1,62 @@
[...]
> 
> 
> > Maybe instead of creating a generic binding just make a binding for
> > these diodes parts? It certainly looks like a generic binding could come
> > later when another vendor supports the same binding.
> 
> I was actually primarily aiming at solving the Rock 5 ITX clock generator
> issue described in patch 5, where the 100 MHz clock generator is just
> described as "100MHz,3.3V,3225" in the schematics, but definitly needs
> the supply regulator to be enabled [1].

That looks like a VCO (voltage controlled oscillator). Maybe the
compatible string can be "voltage-oscillator" or "clock-vco" and it can
require the vdd-supply.

Those diodes parts look different. They look like PLLs that have a
reference clock, hence the 'clocks' property I was expecting to see.
That would use the VCO you have to make the PCIE reference clk
frequencies. A generic compatible for those diodes parts is likely
"phase-locked-loop", or "clock-pll", but I'd avoid that given that PLLs
are almost always complicated and can have multiple output frequencies
if they have post and pre-dividers, etc. It's easier to be specific
here and make a binding for the part you have.