linux-kernel - [PATCH v2 2/3] clk: conf: Support assigned-clock-sscs

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Message-Id: <20250901-clk-ssc-version1-v2-2-1d0a486dffe6@nxp.com>
Date: Mon, 01 Sep 2025 11:51:46 +0800
From: Peng Fan <peng.fan@....com>
To: 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>
Cc: Brian Masney <bmasney@...hat.com>, 
 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, Peng Fan <peng.fan@....com>
Subject: [PATCH v2 2/3] clk: conf: Support assigned-clock-sscs

Parse the Spread Spectrum Configuration(SSC) from device tree and configure
them before using the clock.

Each SSC is three u32 elements which means '<modfreq spreaddepth
modmethod>', so assigned-clock-sscs is an array of multiple three u32
elements.

Signed-off-by: Peng Fan <peng.fan@....com>
---
 drivers/clk/clk-conf.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)

diff --git a/drivers/clk/clk-conf.c b/drivers/clk/clk-conf.c
index 303a0bb26e54a95655ce094a35b989c97ebc6fd8..dd6083597db3f8f27d86abf5640dfc3fb39a9b88 100644
--- a/drivers/clk/clk-conf.c
+++ b/drivers/clk/clk-conf.c
@@ -155,6 +155,71 @@ static int __set_clk_rates(struct device_node *node, bool clk_supplier)
 	return 0;
 }
 
+static int __set_clk_spread_spectrum(struct device_node *node, bool clk_supplier)
+{
+	struct clk_spread_spectrum *sscs __free(kfree) = NULL;
+	u32 elem_size = sizeof(struct clk_spread_spectrum);
+	struct of_phandle_args clkspec;
+	int rc, count, index;
+	struct clk *clk;
+
+	/* modfreq, spreadPercent, modmethod */
+	count = of_property_count_elems_of_size(node, "assigned-clock-sscs", elem_size);
+	if (count <= 0)
+		return 0;
+
+	sscs = kcalloc(count, elem_size, GFP_KERNEL);
+	if (!sscs)
+		return -ENOMEM;
+
+	rc = of_property_read_u32_array(node, "assigned-clock-sscs", (u32 *)sscs,
+					count * 3);
+	if (rc)
+		return rc;
+
+	for (index = 0; index < count; index++) {
+		struct clk_spread_spectrum *conf = &sscs[index];
+		struct clk_hw *hw;
+
+		if (!conf->modfreq_hz && !conf->spread_bp && !conf->method)
+			continue;
+
+		rc = of_parse_phandle_with_args(node, "assigned-clocks", "#clock-cells",
+						index, &clkspec);
+		if (rc < 0) {
+			/* skip empty (null) phandles */
+			if (rc == -ENOENT)
+				continue;
+			else
+				return rc;
+		}
+
+		if (clkspec.np == node && !clk_supplier) {
+			of_node_put(clkspec.np);
+			return 0;
+		}
+
+		clk = of_clk_get_from_provider(&clkspec);
+		of_node_put(clkspec.np);
+		if (IS_ERR(clk)) {
+			if (PTR_ERR(clk) != -EPROBE_DEFER)
+				pr_warn("clk: couldn't get clock %d for %pOF\n",
+					index, node);
+			return PTR_ERR(clk);
+		}
+
+		hw = __clk_get_hw(clk);
+		rc = clk_hw_set_spread_spectrum(hw, conf);
+		if (rc < 0)
+			pr_err("clk: couldn't set %s clk spread spectrum %u %u %u: %d\n",
+			       __clk_get_name(clk), conf->modfreq_hz, conf->spread_bp,
+			       conf->method, rc);
+		clk_put(clk);
+	}
+
+	return 0;
+}
+
 /**
  * of_clk_set_defaults() - parse and set assigned clocks configuration
  * @node: device node to apply clock settings for
@@ -174,6 +239,10 @@ int of_clk_set_defaults(struct device_node *node, bool clk_supplier)
 	if (!node)
 		return 0;
 
+	rc = __set_clk_spread_spectrum(node, clk_supplier);
+	if (rc < 0)
+		return rc;
+
 	rc = __set_clk_parents(node, clk_supplier);
 	if (rc < 0)
 		return rc;

-- 
2.37.1