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

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Message-ID: <20250924-dark-super-gharial-246400@sudeepholla>
Date: Wed, 24 Sep 2025 14:13:18 +0100
From: Sudeep Holla <sudeep.holla@....com>
To: Peng Fan <peng.fan@....com>
Cc: Sebin Francis <sebin.francis@...com>,
	Michael Turquette <mturquette@...libre.com>,
	Sudeep Holla <sudeep.holla@....com>,
	Stephen Boyd <sboyd@...nel.org>,
	Cristian Marussi <cristian.marussi@....com>,
	"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

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.

-- 
Regards,
Sudeep