linux-kernel - [PATCH 3/3] clk: scmi: Support spread spectrum

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Message-Id: <20250124-clk-ssc-v1-3-2d39f6baf2af@nxp.com>
Date: Fri, 24 Jan 2025 22:25:19 +0800
From: "Peng Fan (OSS)" <peng.fan@....nxp.com>
To: Michael Turquette <mturquette@...libre.com>, 
 Stephen Boyd <sboyd@...nel.org>, Russell King <linux@...linux.org.uk>, 
 Sudeep Holla <sudeep.holla@....com>, 
 Cristian Marussi <cristian.marussi@....com>
Cc: linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org, 
 arm-scmi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk@...nel.org>, 
 Dario Binacchi <dario.binacchi@...rulasolutions.com>, 
 Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>, 
 Pengutronix Kernel Team <kernel@...gutronix.de>, 
 Fabio Estevam <festevam@...il.com>, imx@...ts.linux.dev, 
 Peng Fan <peng.fan@....com>
Subject: [PATCH 3/3] clk: scmi: Support spread spectrum

From: Peng Fan <peng.fan@....com>

Support Spread Spectrum for i.MX95 with adding
scmi_clk_set_spread_spectrum_imx

Signed-off-by: Peng Fan <peng.fan@....com>
---
 drivers/clk/clk-scmi.c        | 37 +++++++++++++++++++++++++++++++++++++
 include/linux/scmi_protocol.h |  5 +++++
 2 files changed, 42 insertions(+)

diff --git a/drivers/clk/clk-scmi.c b/drivers/clk/clk-scmi.c
index 15510c2ff21c0335f5cb30677343bd4ef59c0738..e43902aea6bee3633f8328acddcf54eef907b640 100644
--- a/drivers/clk/clk-scmi.c
+++ b/drivers/clk/clk-scmi.c
@@ -98,6 +98,35 @@ static int scmi_clk_set_parent(struct clk_hw *hw, u8 parent_index)
 	return scmi_proto_clk_ops->parent_set(clk->ph, clk->id, parent_index);
 }
 
+static int scmi_clk_set_spread_spectrum_imx(struct clk_hw *hw,
+					    struct clk_spread_spectrum *clk_ss)
+{
+	struct scmi_clk *clk = to_scmi_clk(hw);
+	int ret;
+	u32 val;
+
+	/* SCMI OEM Duty Cycle is expressed as a percentage */
+	/*
+	 * extConfigValue[7:0]   - spread percentage (%)
+	 * extConfigValue[23:8]  - Modulation Frequency (KHz)
+	 * extConfigValue[24]    - Enable/Disable
+	 * extConfigValue[31:25] - Reserved
+	 */
+	val = FIELD_PREP(IMX_CLOCK_EXT_SS_PERCENTAGE_MASK, clk_ss->spreadpercent);
+	val |= FIELD_PREP(IMX_CLOCK_EXT_SS_MOD_FREQ_MASK, clk_ss->modfreq);
+	val |= IMX_CLOCK_EXT_SS_ENABLE_MASK;
+	ret = scmi_proto_clk_ops->config_oem_set(clk->ph, clk->id,
+						 SCMI_CLOCK_CFG_NXP_IMX_SSC,
+						 val, false);
+	if (ret)
+		dev_warn(clk->dev,
+			 "Failed to set spread spectrum(%u,%u,%u) for clock ID %d\n",
+			 clk_ss->modfreq, clk_ss->spreadpercent, clk_ss->method,
+			 clk->id);
+
+	return ret;
+}
+
 static u8 scmi_clk_get_parent(struct clk_hw *hw)
 {
 	struct scmi_clk *clk = to_scmi_clk(hw);
@@ -266,6 +295,11 @@ static int scmi_clk_ops_init(struct device *dev, struct scmi_clk *sclk,
  * Return: A pointer to the allocated and configured clk_ops on success,
  *	   or NULL on allocation failure.
  */
+static const char * const scmi_clk_ssc_allowlist[] = {
+	"fsl,imx95",
+	NULL
+};
+
 static const struct clk_ops *
 scmi_clk_ops_alloc(struct device *dev, unsigned long feats_key)
 {
@@ -316,6 +350,9 @@ scmi_clk_ops_alloc(struct device *dev, unsigned long feats_key)
 		ops->set_duty_cycle = scmi_clk_set_duty_cycle;
 	}
 
+	if (of_machine_compatible_match(scmi_clk_ssc_allowlist))
+		ops->set_spread_spectrum = scmi_clk_set_spread_spectrum_imx;
+
 	return ops;
 }
 
diff --git a/include/linux/scmi_protocol.h b/include/linux/scmi_protocol.h
index 688466a0e816247d24704f7ba109667a14226b67..7012d5efef00eb7b52f17d0f3d8d69f3d0063557 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_NXP_IMX_SSC = 0x80,
 	SCMI_CLOCK_CFG_OEM_END = 0xFF,
 };
 
+#define IMX_CLOCK_EXT_SS_PERCENTAGE_MASK	GENMASK(7, 0)
+#define IMX_CLOCK_EXT_SS_MOD_FREQ_MASK		GENMASK(23, 8)
+#define IMX_CLOCK_EXT_SS_ENABLE_MASK		BIT(24)
+
 /**
  * struct scmi_clk_proto_ops - represents the various operations provided
  *	by SCMI Clock Protocol

-- 
2.35.3