[PATCH 3/3] clk: scmi: Support spread spectrum

Peng Fan (OSS)
2025-01-24T13:19:21Z

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

Support Spread Spectrum for i.MX95 with adding
scmi_clk_set_spread_spectrum_imx

Signed-off-by: Peng Fan <peng.fan@nxp.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