linux-kernel - RE: [PATCH v4 5/5] clk: scmi: Support Spread Spectrum for NXP i.MX95

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Message-ID:
 <PAXPR04MB84592331881F5C0C529C7B66881CA@PAXPR04MB8459.eurprd04.prod.outlook.com>
Date: Wed, 24 Sep 2025 14:35:30 +0000
From: Peng Fan <peng.fan@....com>
To: Sudeep Holla <sudeep.holla@....com>, Sebin Francis <sebin.francis@...com>,
	Cristian Marussi <cristian.marussi@....com>
CC: Michael Turquette <mturquette@...libre.com>, Stephen Boyd
	<sboyd@...nel.org>, Marco Felsch <m.felsch@...gutronix.de>, Rob Herring
	<robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
	<conor+dt@...nel.org>, Brian Masney <bmasney@...hat.com>, Dan Carpenter
	<dan.carpenter@...aro.org>, Geert Uytterhoeven <geert@...ux-m68k.org>,
	"linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"arm-scmi@...r.kernel.org" <arm-scmi@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>
Subject: RE: [PATCH v4 5/5] clk: scmi: Support Spread Spectrum for NXP i.MX95

Hi Sudeep,

> Subject: Re: [PATCH v4 5/5] clk: scmi: Support Spread Spectrum for
> NXP i.MX95
> 
> On Wed, Sep 24, 2025 at 11:43:56AM +0000, Peng Fan wrote:
> > > Subject: Re: [PATCH v4 5/5] clk: scmi: Support Spread Spectrum for
> > > NXP i.MX95
> > ...
> > > >>>        SCMI_CLOCK_CFG_OEM_START = 0x80,
> > > >>> +     SCMI_CLOCK_CFG_IMX_SSC = 0x80,
> > > >>
> > > >> TI is also planning to implement the same in our upcoming
> platform.
> > > >> so can we use a generic ID instead of vender specfic message ID?
> > > >
> > > > I tried to push to new generic ID [1] in half a year ago, but in
> > > > the end ARM decided not to add generic ID for spread spectrum
> support.
> > > >
> > > > To i.MX, it is too late to use a generic ID and waiting spec, i.MX
> > > > firmware has been public for quite some time and passed several
> > > external releases.
> > > > So I need to use what our firmware adds and spec allows: vendor
> > > > extension.
> > >
> > > Thanks for the quick response,
> > > Since this implementation is specific to i.MX, can you move this to
> > > a vendor specific file, so that it will not break i.MX's firmware
> > > and TI can implement SSC in TI specific file.
> >
> > i.MX has encountered issue with pinctrl-scmi.c and pinctrl-imx-scmi.c
> > both supports SCMI PINCTRL. Current linux scmi does not support
> both
> > drivers built in kernel image, because scmi devlink issue.
> >
> > Sudeep said he would address the devlink issue in 6.19 cycle.
> >
> 
> Yes it is a different issue IMO and nothing related to this.
> 
> > Given the current situation, I'm hesitant to introduce a new driver
> > saying clk-imx-scmi.c.
> >
> 
> Yes please don't, and I don't see a strong reason for that(yet).
> 
> Unlike vendor protocol, there is no way we can no upfront how the
> vendors can use this in their own colourful way. So I am not sure if we
> start building something generic from the start or refactor as more
> vendors start using it. Hard to decide 🙁. Lets see, need to think a bit.
> 
> If Peng or Sebin or others have some idea, please propose or start the
> discussion so that we can evaluate the approach.

I would give a look and hope there is an output. I will start
a new thread to discuss.

Just in my mind
Each standard protocol has its own OEM or vendor description, it might
be hard to use a generic way to support all standard protocols.

It might be a bit easier to use per protocol extension.

Anyway, let's discuss in the new thread with potential solutions.

Thanks
Peng. 

> 
> --
> Regards,
> Sudeep