linux-kernel - Re: [PATCH v5 6/6] clk: scmi: Add i.MX95 OEM extension support for SCMI clock driver

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Message-ID: <CAMuHMdU-UkzLnrPpBVyMH0DtgubxE_spUYbxtpO+5dmkFFqdcQ@mail.gmail.com>
Date: Thu, 23 Oct 2025 15:58:35 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Peng Fan <peng.fan@....com>
Cc: Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Sudeep Holla <sudeep.holla@....com>, Cristian Marussi <cristian.marussi@....com>, 
	Sebin Francis <sebin.francis@...com>, Brian Masney <bmasney@...hat.com>, 
	Dan Carpenter <dan.carpenter@...aro.org>, linux-kernel@...r.kernel.org, 
	linux-clk@...r.kernel.org, devicetree@...r.kernel.org, 
	arm-scmi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v5 6/6] clk: scmi: Add i.MX95 OEM extension support for
 SCMI clock driver

Hi Peng,

On Thu, 9 Oct 2025 at 05:49, Peng Fan <peng.fan@....com> wrote:
>  - Introduce 'clk-scmi-oem.c' to support vendor-specific OEM extensions
>    for the SCMI clock driver, allows clean integration of vendor-specific
>    features without impacting the core SCMI clock driver logic.
>  - Extend 'clk-scmi.h' with 'scmi_clk_oem' structure and related declarations.
>  - Initialize OEM extensions via 'scmi_clk_oem_init()'.
>  - Support querying OEM-specific features and setting spread spectrum.
>  - Pass 'scmi_device' to 'scmi_clk_ops_select()' for OEM data access.
>
> Signed-off-by: Peng Fan <peng.fan@....com>

Thanks for your patch!

> --- /dev/null
> +++ b/drivers/clk/clk-scmi-oem.c
> @@ -0,0 +1,103 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * The Vendor OEM extension for System Control and Power Interface (SCMI)
> + * Protocol based clock driver
> + *
> + * Copyright 2025 NXP
> + */
> +
> +#include <linux/clk-provider.h>
> +#include <linux/of.h>
> +#include <linux/scmi_imx_protocol.h>
> +#include <linux/scmi_protocol.h>
> +
> +#include "clk-scmi.h"
> +
> +#define SCMI_CLOCK_CFG_IMX_SSC                 0x80
> +#define SCMI_CLOCK_IMX_SS_PERCENTAGE_MASK      GENMASK(7, 0)
> +#define SCMI_CLOCK_IMX_SS_MOD_FREQ_MASK                GENMASK(23, 8)
> +#define SCMI_CLOCK_IMX_SS_ENABLE_MASK          BIT(24)
> +
> +struct scmi_clk_oem_info {
> +       char *vendor_id;
> +       char *sub_vendor_id;
> +       char *compatible;
> +       const void *data;
> +};
> +
> +static int
> +scmi_clk_imx_set_spread_spectrum(struct clk_hw *hw,
> +                                const struct clk_spread_spectrum *ss_conf)
> +{
> +       struct scmi_clk *clk = to_scmi_clk(hw);
> +       int ret;
> +       u32 val;
> +
> +       /*
> +        * extConfigValue[7:0]   - spread percentage (%)
> +        * extConfigValue[23:8]  - Modulation Frequency

What is the unit of this?
According to the code below, it is in Hz, so it is limited to 65535 Hz.

> +        * extConfigValue[24]    - Enable/Disable
> +        * extConfigValue[31:25] - Reserved

Center, up, down, could be stored here, I assume?

> +        */
> +       val = FIELD_PREP(SCMI_CLOCK_IMX_SS_PERCENTAGE_MASK, ss_conf->spread_bp / 10000);
> +       val |= FIELD_PREP(SCMI_CLOCK_IMX_SS_MOD_FREQ_MASK, ss_conf->modfreq_hz);
> +       if (ss_conf->method != CLK_SPREAD_NO)
> +               val |= SCMI_CLOCK_IMX_SS_ENABLE_MASK;
> +       ret = scmi_proto_clk_ops->config_oem_set(clk->ph, clk->id,
> +                                                SCMI_CLOCK_CFG_IMX_SSC,
> +                                                val, false);
> +       if (ret)
> +               dev_warn(clk->dev,
> +                        "Failed to set spread spectrum(%u,%u,%u) for clock ID %d\n",
> +                        ss_conf->modfreq_hz, ss_conf->spread_bp, ss_conf->method,
> +                        clk->id);
> +
> +       return ret;
> +}

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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