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Message-Id: <20250812-clk-ssc-version1-v1-3-cef60f20d770@nxp.com>
Date: Tue, 12 Aug 2025 20:17:07 +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: 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 3/3] clk: scmi: Support Spread Spectrum for NXP i.MX95
The PLL clocks on NXP i.MX95 SoCs support Spread Spectrum (SS).
This patch introduces scmi_clk_imx_set_spread_spectrum to pass SS
configuration to the SCMI firmware, which handles the actual
implementation.
To ensure this feature is only enabled on NXP platforms,
scmi_clk_imx_extended_config_oem is added. Since SS is only applicable
to PLL clocks, config_oem_get is used to verify SS support for a given
clock.
i.MX95 SCMI firmware Spread Spectrum extConfigValue definition is as
below, no modulation method because firmware forces to use down spread.
extConfigValue[7:0] - spread percentage (%)
extConfigValue[23:8] - Modulation Frequency (KHz)
extConfigValue[24] - Enable/Disable
extConfigValue[31:25] - Reserved
Signed-off-by: Peng Fan <peng.fan@....com>
---
drivers/clk/clk-scmi.c | 64 ++++++++++++++++++++++++++++++++++++++++---
include/linux/scmi_protocol.h | 5 ++++
2 files changed, 65 insertions(+), 4 deletions(-)
diff --git a/drivers/clk/clk-scmi.c b/drivers/clk/clk-scmi.c
index d2408403283fc72f0cf902e65f4c08bcbc7b4b0b..bb5e20dab18e92932ab4b99192b496e0c4d96417 100644
--- a/drivers/clk/clk-scmi.c
+++ b/drivers/clk/clk-scmi.c
@@ -12,6 +12,7 @@
#include <linux/of.h>
#include <linux/module.h>
#include <linux/scmi_protocol.h>
+#include <linux/scmi_imx_protocol.h>
#include <asm/div64.h>
#define NOT_ATOMIC false
@@ -23,6 +24,7 @@ enum scmi_clk_feats {
SCMI_CLK_RATE_CTRL_SUPPORTED,
SCMI_CLK_PARENT_CTRL_SUPPORTED,
SCMI_CLK_DUTY_CYCLE_SUPPORTED,
+ SCMI_CLK_IMX_SSC_SUPPORTED,
SCMI_CLK_FEATS_COUNT
};
@@ -98,6 +100,35 @@ 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_imx_set_spread_spectrum(struct clk_hw *hw,
+ struct clk_spread_spectrum *clk_ss)
+{
+ struct scmi_clk *clk = to_scmi_clk(hw);
+ int ret;
+ u32 val;
+
+ /*
+ * extConfigValue[7:0] - spread percentage (%)
+ * extConfigValue[23:8] - Modulation Frequency
+ * extConfigValue[24] - Enable/Disable
+ * extConfigValue[31:25] - Reserved
+ */
+ val = FIELD_PREP(SCMI_CLOCK_IMX_SS_PERCENTAGE_MASK, clk_ss->spread_bp / 10000);
+ val |= FIELD_PREP(SCMI_CLOCK_IMX_SS_MOD_FREQ_MASK, clk_ss->modfreq_hz);
+ if (clk_ss->method != CLK_SSC_NO_SPREAD)
+ val |= SCMI_CLOCK_IMX_SS_ENABLE_MASK;
+ ret = scmi_proto_clk_ops->config_oem_set(clk->ph, clk->id,
+ SCMI_CLOCK_CFG_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_hz, clk_ss->spread_bp, 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);
@@ -316,11 +347,33 @@ scmi_clk_ops_alloc(struct device *dev, unsigned long feats_key)
ops->set_duty_cycle = scmi_clk_set_duty_cycle;
}
+ if (feats_key & BIT(SCMI_CLK_IMX_SSC_SUPPORTED))
+ ops->set_spread_spectrum = scmi_clk_imx_set_spread_spectrum;
+
return ops;
}
+static void scmi_clk_imx_extended_config_oem(const struct scmi_handle *handle,
+ struct scmi_clk *sclk,
+ unsigned int *feats_key)
+{
+ int ret;
+ u32 val;
+
+ if (strcmp(handle->version->vendor_id, SCMI_IMX_VENDOR) ||
+ strcmp(handle->version->sub_vendor_id, SCMI_IMX_SUBVENDOR))
+ return;
+
+ ret = scmi_proto_clk_ops->config_oem_get(sclk->ph, sclk->id,
+ SCMI_CLOCK_CFG_IMX_SSC,
+ &val, NULL, false);
+ if (!ret)
+ *feats_key |= BIT(SCMI_CLK_IMX_SSC_SUPPORTED);
+}
+
/**
* scmi_clk_ops_select() - Select a proper set of clock operations
+ * @handle: A reference to an SCMI entity
* @sclk: A reference to an SCMI clock descriptor
* @atomic_capable: A flag to indicate if atomic mode is supported by the
* transport
@@ -345,8 +398,8 @@ scmi_clk_ops_alloc(struct device *dev, unsigned long feats_key)
* NULL otherwise.
*/
static const struct clk_ops *
-scmi_clk_ops_select(struct scmi_clk *sclk, bool atomic_capable,
- unsigned int atomic_threshold_us,
+scmi_clk_ops_select(const struct scmi_handle *handle, struct scmi_clk *sclk,
+ bool atomic_capable, unsigned int atomic_threshold_us,
const struct clk_ops **clk_ops_db, size_t db_size)
{
const struct scmi_clock_info *ci = sclk->info;
@@ -370,9 +423,12 @@ scmi_clk_ops_select(struct scmi_clk *sclk, bool atomic_capable,
if (!ci->parent_ctrl_forbidden)
feats_key |= BIT(SCMI_CLK_PARENT_CTRL_SUPPORTED);
- if (ci->extended_config)
+ if (ci->extended_config) {
feats_key |= BIT(SCMI_CLK_DUTY_CYCLE_SUPPORTED);
+ scmi_clk_imx_extended_config_oem(handle, sclk, &feats_key);
+ }
+
if (WARN_ON(feats_key >= db_size))
return NULL;
@@ -459,7 +515,7 @@ static int scmi_clocks_probe(struct scmi_device *sdev)
* to avoid sharing the devm_ allocated clk_ops between multiple
* SCMI clk driver instances.
*/
- scmi_ops = scmi_clk_ops_select(sclk, transport_is_atomic,
+ scmi_ops = scmi_clk_ops_select(handle, sclk, transport_is_atomic,
atomic_threshold_us,
scmi_clk_ops_db,
ARRAY_SIZE(scmi_clk_ops_db));
diff --git a/include/linux/scmi_protocol.h b/include/linux/scmi_protocol.h
index 688466a0e816247d24704f7ba109667a14226b67..6f9f197ee671540e38470a5666eb5ba8ec9de439 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_IMX_SSC = 0x80,
SCMI_CLOCK_CFG_OEM_END = 0xFF,
};
+#define SCMI_CLOCK_IMX_SS_PERCENTAGE_MASK GENMASK(7, 0)
+#define SCMI_CLOCK_IMX_SS_MOD_FREQ_MASK GENMASK(23, 8)
+#define SCMI_CLOCK_IMX_SS_ENABLE_MASK BIT(24)
+
/**
* struct scmi_clk_proto_ops - represents the various operations provided
* by SCMI Clock Protocol
--
2.37.1
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