[PATCH v2 1/4] clk: Introduce clk_hw_set_spread_spectrum

Peng Fan (OSS)
2025-02-05T09:50:59Z

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

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.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
---
drivers/clk/clk.c | 34 ++++++++++++++++++++++++++++++++++
include/linux/clk-provider.h | 32 ++++++++++++++++++++++++++++++++
include/linux/clk.h | 22 ++++++++++++++++++++++
3 files changed, 88 insertions(+)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index cf7720b9172ff223d86227aad144e15375ddfd86..e11f9615e683af52c719d4c8419bd30f369f301b 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -2790,6 +2790,40 @@ 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, unsigned int modfreq,
+ unsigned int spreaddepth, enum clk_ssc_method method,
+ bool enable)
+{
+ struct clk_spread_spectrum clk_ss;
+ struct clk_core *core;
+ int ret;
+
+ if (!hw)
+ return 0;
+
+ core = hw->core;
+
+ clk_ss.modfreq = modfreq;
+ clk_ss.spreaddepth = spreaddepth;
+ clk_ss.method = method;
+ clk_ss.enable = enable;
+
+ 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, &clk_ss);
+
+ clk_pm_runtime_put(core);
+
+fail:
+ clk_prepare_unlock();
+ return ret;
+}
+
/**
* 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 2e6e603b749342931c0d0693c3e72b62c000791b..ac0270cc9ec133954b1f8dcffed015723bd1ff5d 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -84,6 +84,28 @@ struct clk_duty {
unsigned int den;
};

+/* Aligned with dtschema/schemas/clock/clock.yaml */
+enum clk_ssc_method {
+ CLK_SSC_CENTER_SPREAD,
+ CLK_SSC_UP_SPREAD,
+ CLK_SSC_DOWN_SPREAD,
+};
+
+/**
+ * struct clk_spread_spectrum - Structure encoding spread spectrum of a clock
+ *
+ * @modfreq: Modulation frequency
+ * @spreadpercent: Modulation percent
+ * @method: Modulation method
+ * @enable: Modulation enable or disable
+ */
+struct clk_spread_spectrum {
+ unsigned int modfreq;
+ unsigned int spreaddepth;
+ enum clk_ssc_method method;
+ bool enable;
+};
+
/**
* 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 +200,11 @@ struct clk_duty {
* separately via calls to .set_parent and .set_rate.
* Returns 0 on success, -EERROR otherwise.
*
+ * @set_spread_spectrum: Configure the modulation frequency, modulation percentage
+ * and method. This callback is optional for clocks that does not
+ * support spread spectrum feature or no need to enable this feature.
+ * 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,
+ struct clk_spread_spectrum *clk_ss);
unsigned long (*recalc_accuracy)(struct clk_hw *hw,
unsigned long parent_accuracy);
int (*get_phase)(struct clk_hw *hw);
@@ -1404,6 +1433,9 @@ 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, unsigned int modfreq,
+ unsigned int spreaddepth, enum clk_ssc_method method,
+ bool enable);

static inline void __clk_hw_set_clk(struct clk_hw *dst, struct clk_hw *src)
{
diff --git a/include/linux/clk.h b/include/linux/clk.h
index b607482ca77e987b9344c38f25ebb5c8d35c1d39..49a7f7eb8b03233e11cd3b92768896c4e45c4e7c 100644
--- a/include/linux/clk.h
+++ b/include/linux/clk.h
@@ -858,6 +858,21 @@ int clk_set_rate(struct clk *clk, unsigned long rate);
*/
int clk_set_rate_exclusive(struct clk *clk, unsigned long rate);

+/**
+ * clk_set_spread_spectrum - set the spread spectrum for a clock
+ * @clk: clock source
+ * @modfreq: modulation freq
+ * @spreadpercent: modulation percentage
+ * @method: down spread, up spread, center spread or else
+ * @enable: enable or disable
+ *
+ * Configure the spread spectrum parameters for a clock.
+ *
+ * Returns success (0) or negative errno.
+ */
+int clk_set_spread_spectrum(struct clk *clk, unsigned int modfreq,
+ unsigned int spreadpercent, unsigned int method,
+ bool enable);
/**
* clk_has_parent - check if a clock is a possible parent for another
* @clk: clock source
@@ -1088,6 +1103,13 @@ static inline int clk_set_rate_exclusive(struct clk *clk, unsigned long rate)
return 0;
}

+static inline int clk_set_spread_spectrum(struct clk *clk, unsigned int modfreq,
+ unsigned int spreadpercent,
+ unsigned int method, bool enable)
+{
+ return 0;
+}
+
static inline long clk_round_rate(struct clk *clk, unsigned long rate)
{
return 0;

--
2.37.1