[PATCH v6 2/6] clk: Introduce clk_hw_set_spread_spectrum

Peng Fan (OSS)
2025-11-28T03:14:37Z

Add clk_hw_set_spread_spectrum to configure a clock to enable spread
spectrum feature. set_spread_spectrum ops is added for clk drivers to
have their own hardware specific implementation.

Reviewed-by: Brian Masney <bmasney@redhat.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
---
drivers/clk/clk.c | 27 +++++++++++++++++++++++++++
include/linux/clk-provider.h | 31 +++++++++++++++++++++++++++++++
2 files changed, 58 insertions(+)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 85d2f2481acf360f0618a4a382fb51250e9c2fc4..6cd941a729590b501d66101e352b99e51ca18464 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -2784,6 +2784,33 @@ int clk_set_max_rate(struct clk *clk, unsigned long rate)
}
EXPORT_SYMBOL_GPL(clk_set_max_rate);

+int clk_hw_set_spread_spectrum(struct clk_hw *hw, const struct clk_spread_spectrum *ss_conf)
+{
+ struct clk_core *core;
+ int ret;
+
+ if (!hw)
+ return 0;
+
+ core = hw->core;
+
+ clk_prepare_lock();
+
+ ret = clk_pm_runtime_get(core);
+ if (ret)
+ goto fail;
+
+ if (core->ops->set_spread_spectrum)
+ ret = core->ops->set_spread_spectrum(hw, ss_conf);
+
+ clk_pm_runtime_put(core);
+
+fail:
+ clk_prepare_unlock();
+ return ret;
+}
+EXPORT_SYMBOL_GPL(clk_hw_set_spread_spectrum);
+
/**
* clk_get_parent - return the parent of a clk
* @clk: the clk whose parent gets returned
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 630705a47129453c241f1b1755f2c2f2a7ed8f77..9ec25bbccd613eafd77aca080dd7f51b1bfdadc1 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -6,6 +6,7 @@
#ifndef __LINUX_CLK_PROVIDER_H
#define __LINUX_CLK_PROVIDER_H

+#include <dt-bindings/clock/clock.h>
#include <linux/of.h>
#include <linux/of_clk.h>

@@ -84,6 +85,26 @@ struct clk_duty {
unsigned int den;
};

+enum clk_ssc_method {
+ CLK_SPREAD_NO = CLK_SSC_NO_SPREAD,
+ CLK_SPREAD_CENTER = CLK_SSC_CENTER_SPREAD,
+ CLK_SPREAD_UP = CLK_SSC_UP_SPREAD,
+ CLK_SPREAD_DOWN = CLK_SSC_DOWN_SPREAD,
+};
+
+/**
+ * struct clk_spread_spectrum - Structure encoding spread spectrum of a clock
+ *
+ * @modfreq_hz: Modulation frequency
+ * @spread_bp: Modulation percent in permyriad
+ * @method: Modulation method
+ */
+struct clk_spread_spectrum {
+ u32 modfreq_hz;
+ u32 spread_bp;
+ enum clk_ssc_method method;
+};
+
/**
* struct clk_ops - Callback operations for hardware clocks; these are to
* be provided by the clock implementation, and will be called by drivers
@@ -178,6 +199,12 @@ struct clk_duty {
* separately via calls to .set_parent and .set_rate.
* Returns 0 on success, -EERROR otherwise.
*
+ * @set_spread_spectrum: Optional callback used to configure the spread
+ * spectrum modulation frequency, percentage, and method
+ * to reduce EMI by spreading the clock frequency over a
+ * wider range.
+ * Returns 0 on success, -EERROR otherwise.
+ *
* @recalc_accuracy: Recalculate the accuracy of this clock. The clock accuracy
* is expressed in ppb (parts per billion). The parent accuracy is
* an input parameter.
@@ -255,6 +282,8 @@ struct clk_ops {
int (*set_rate_and_parent)(struct clk_hw *hw,
unsigned long rate,
unsigned long parent_rate, u8 index);
+ int (*set_spread_spectrum)(struct clk_hw *hw,
+ const struct clk_spread_spectrum *ss_conf);
unsigned long (*recalc_accuracy)(struct clk_hw *hw,
unsigned long parent_accuracy);
int (*get_phase)(struct clk_hw *hw);
@@ -1430,6 +1459,8 @@ void clk_hw_get_rate_range(struct clk_hw *hw, unsigned long *min_rate,
unsigned long *max_rate);
void clk_hw_set_rate_range(struct clk_hw *hw, unsigned long min_rate,
unsigned long max_rate);
+int clk_hw_set_spread_spectrum(struct clk_hw *hw,
+ const struct clk_spread_spectrum *ss_conf);

static inline void __clk_hw_set_clk(struct clk_hw *dst, struct clk_hw *src)
{

--
2.37.1