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

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Message-ID: <5f508f1d-2d08-4687-86cd-d1944caa0a49@ti.com>
Date: Tue, 23 Sep 2025 16:22:31 +0530
From: Sebin Francis <sebin.francis@...com>
To: Peng Fan <peng.fan@....com>, Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, Sudeep Holla <sudeep.holla@....com>,
        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>
CC: Dan Carpenter <dan.carpenter@...aro.org>,
        Geert Uytterhoeven
	<geert@...ux-m68k.org>,
        <linux-clk@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <arm-scmi@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH v4 5/5] clk: scmi: Support Spread Spectrum for NXP i.MX95

Hi Peng

On 15/09/25 13:59, Peng Fan wrote:
> The PLL clocks on NXP i.MX95 SoCs support Spread Spectrum (SS).
> This patch introduces scmi_clk_imx_set_spread_spectrum to pass SS
> configuration to the SCMI firmware, which handles the actual
> implementation.
> 
> To ensure this feature is only enabled on NXP platforms,
> scmi_clk_imx_extended_config_oem is added. Since SS is only applicable
> to PLL clocks, config_oem_get is used to verify SS support for a given
> clock.
> 
> i.MX95 SCMI firmware Spread Spectrum extConfigValue definition is as
> below, no modulation method because firmware forces to use down spread.
> 	 extConfigValue[7:0]   - spread percentage (%)
> 	 extConfigValue[23:8]  - Modulation Frequency (KHz)
> 	 extConfigValue[24]    - Enable/Disable
> 	 extConfigValue[31:25] - Reserved
> 
> Signed-off-by: Peng Fan <peng.fan@....com>
> ---

...

>   	if (WARN_ON(feats_key >= db_size))
>   		return NULL;
>   
> @@ -459,7 +515,7 @@ static int scmi_clocks_probe(struct scmi_device *sdev)
>   		 * to avoid sharing the devm_ allocated clk_ops between multiple
>   		 * SCMI clk driver instances.
>   		 */
> -		scmi_ops = scmi_clk_ops_select(sclk, transport_is_atomic,
> +		scmi_ops = scmi_clk_ops_select(handle, sclk, transport_is_atomic,
>   					       atomic_threshold_us,
>   					       scmi_clk_ops_db,
>   					       ARRAY_SIZE(scmi_clk_ops_db));
> diff --git a/include/linux/scmi_protocol.h b/include/linux/scmi_protocol.h
> index aafaac1496b06a6e4f0ca32eee58a9edf7d4a70f..37f422b4b1ef2af2b4231a1677161aa24e07d0e2 100644
> --- a/include/linux/scmi_protocol.h
> +++ b/include/linux/scmi_protocol.h
> @@ -80,9 +80,14 @@ enum scmi_clock_oem_config {
>   	SCMI_CLOCK_CFG_DUTY_CYCLE = 0x1,
>   	SCMI_CLOCK_CFG_PHASE,
>   	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?

>   	SCMI_CLOCK_CFG_OEM_END = 0xFF,
>   };
>   
> +#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_proto_ops - represents the various operations provided
>    *	by SCMI Clock Protocol
> 

Thanks
Sebin