[PATCH v6 17/18] clk: imx: pll14xx: support spread spectrum clock generation

From: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Date: 2024-12-22 17:06:11
Also in: imx, linux-clk, lkml
Subsystem: common clk framework, nxp i.mx clock drivers, the rest · Maintainers: Michael Turquette, Stephen Boyd, Abel Vesa, Linus Torvalds

Add support for spread spectrum clock (SSC) generation to the pll14xxx
driver.

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>

---

Changes in v6:
- Update the code based on the changes made to the DT bindings

 drivers/clk/imx/clk-pll14xx.c | 134 ++++++++++++++++++++++++++++++++++
 drivers/clk/imx/clk.h         |  16 ++++
 2 files changed, 150 insertions(+)

diff --git a/drivers/clk/imx/clk-pll14xx.c b/drivers/clk/imx/clk-pll14xx.c
index d63564dbb12c..c20f1ade9dff 100644
--- a/drivers/clk/imx/clk-pll14xx.c
+++ b/drivers/clk/imx/clk-pll14xx.c

@@ -20,6 +20,8 @@
 #define GNRL_CTL	0x0
 #define DIV_CTL0	0x4
 #define DIV_CTL1	0x8
+#define SSCG_CTRL	0xc
+
 #define LOCK_STATUS	BIT(31)
 #define LOCK_SEL_MASK	BIT(29)
 #define CLKE_MASK	BIT(11)

@@ -31,6 +33,10 @@
 #define KDIV_MASK	GENMASK(15, 0)
 #define KDIV_MIN	SHRT_MIN
 #define KDIV_MAX	SHRT_MAX
+#define SSCG_ENABLE	BIT(31)
+#define MFREQ_CTL_MASK	GENMASK(19, 12)
+#define MRAT_CTL_MASK	GENMASK(9, 4)
+#define SEL_PF_MASK	GENMASK(1, 0)
 
 #define LOCK_TIMEOUT_US		10000

@@ -40,6 +46,8 @@ struct clk_pll14xx {
 	enum imx_pll14xx_type		type;
 	const struct imx_pll14xx_rate_table *rate_table;
 	int rate_count;
+	bool                            ssc_enable;
+	struct imx_pll14xx_ssc		ssc_conf;
 };
 
 #define to_clk_pll14xx(_hw) container_of(_hw, struct clk_pll14xx, hw)

@@ -347,6 +355,27 @@ static int clk_pll1416x_set_rate(struct clk_hw *hw, unsigned long drate,
 	return 0;
 }
 
+static void clk_pll1443x_enable_ssc(struct clk_hw *hw, unsigned long parent_rate,
+				    unsigned int pdiv, unsigned int mdiv)
+{
+	struct clk_pll14xx *pll = to_clk_pll14xx(hw);
+	struct imx_pll14xx_ssc *conf = &pll->ssc_conf;
+	u32 sscg_ctrl, mfr, mrr;
+
+	sscg_ctrl = readl_relaxed(pll->base + SSCG_CTRL);
+	sscg_ctrl &=
+		~(SSCG_ENABLE | MFREQ_CTL_MASK | MRAT_CTL_MASK | SEL_PF_MASK);
+
+	mfr = parent_rate / (conf->mod_freq * pdiv * (1 << 5));
+	mrr = (conf->mod_rate * mdiv * (1 << 6)) / (100 * mfr);
+
+	sscg_ctrl |= SSCG_ENABLE | FIELD_PREP(MFREQ_CTL_MASK, mfr) |
+		FIELD_PREP(MRAT_CTL_MASK, mrr) |
+		FIELD_PREP(SEL_PF_MASK, conf->mod_type);
+
+	writel_relaxed(sscg_ctrl, pll->base + SSCG_CTRL);
+}
+
 static int clk_pll1443x_set_rate(struct clk_hw *hw, unsigned long drate,
 				 unsigned long prate)
 {

@@ -368,6 +397,9 @@ static int clk_pll1443x_set_rate(struct clk_hw *hw, unsigned long drate,
 		writel_relaxed(FIELD_PREP(KDIV_MASK, rate.kdiv),
 			       pll->base + DIV_CTL1);
 
+		if (pll->ssc_enable)
+			clk_pll1443x_enable_ssc(hw, prate, rate.pdiv, rate.mdiv);
+
 		return 0;
 	}

@@ -408,6 +440,9 @@ static int clk_pll1443x_set_rate(struct clk_hw *hw, unsigned long drate,
 	gnrl_ctl &= ~BYPASS_MASK;
 	writel_relaxed(gnrl_ctl, pll->base + GNRL_CTL);
 
+	if (pll->ssc_enable)
+		clk_pll1443x_enable_ssc(hw, prate, rate.pdiv, rate.mdiv);
+
 	return 0;
 }

@@ -542,3 +577,102 @@ struct clk_hw *imx_dev_clk_hw_pll14xx(struct device *dev, const char *name,
 	return hw;
 }
 EXPORT_SYMBOL_GPL(imx_dev_clk_hw_pll14xx);
+
+void imx_clk_pll14xx_enable_ssc(struct clk_hw *hw, struct imx_pll14xx_ssc *conf)
+{
+	struct clk_pll14xx *pll = to_clk_pll14xx(hw);
+
+	pll->ssc_enable = true;
+	memcpy(&pll->ssc_conf, conf, sizeof(pll->ssc_conf));
+}
+EXPORT_SYMBOL_GPL(imx_clk_pll14xx_enable_ssc);
+
+static int clk_pll14xx_ssc_mod_type(const char *name,
+				    enum imx_pll14xx_ssc_mod_type *mod_type)
+{
+	int i;
+	struct {
+		const char *name;
+		enum imx_pll14xx_ssc_mod_type id;
+	} mod_types[] = {
+		{ .name = "down-spread", .id = IMX_PLL14XX_SSC_DOWN_SPREAD },
+		{ .name = "up-spread", .id = IMX_PLL14XX_SSC_UP_SPREAD },
+		{ .name = "center-spread", .id = IMX_PLL14XX_SSC_CENTER_SPREAD }
+	};
+
+	for (i = 0; i < ARRAY_SIZE(mod_types); i++) {
+		if (!strcmp(name, mod_types[i].name)) {
+			*mod_type = mod_types[i].id;
+			return 0;
+		}
+	}
+
+	return -EINVAL;
+}
+
+static int clk_pll14xx_ssc_index(const char *pll_name)
+{
+	static const char *const pll_names[] = {
+		"audio_pll1",
+		"audio_pll2",
+		"dram_pll",
+		"video_pll"
+	};
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(pll_names); i++) {
+		if (!strcmp(pll_names[i], pll_name))
+			return i;
+	}
+
+	return -ENODEV;
+}
+
+int imx_clk_pll14xx_ssc_parse_dt(struct device_node *np, const char *pll_name,
+				 struct imx_pll14xx_ssc *conf)
+{
+	int index, ret;
+	const char *s;
+
+	if (!conf)
+		return -EINVAL;
+
+	index = clk_pll14xx_ssc_index(pll_name);
+	if (index < 0)
+		return index;
+
+	ret = of_property_read_u32_index(np, "fsl,ssc-modfreq-hz", index,
+					 &conf->mod_freq);
+	if (ret)
+		return ret;
+
+	ret = of_property_read_u32_index(np, "fsl,ssc-modrate-percent", index,
+					 &conf->mod_rate);
+	if (ret) {
+		pr_err("missing fsl,ssc-modrate-percent property for %pOFn\n",
+		       np);
+		return ret;
+	}
+
+	ret = of_property_read_string_index(np, "fsl,ssc-modmethod", index, &s);
+	if (ret) {
+		pr_err("failed to get fsl,ssc-modmethod property for %pOFn\n",
+		       np);
+		return ret;
+	}
+
+	if (strlen(s) == 0)
+		return -ENODEV;
+
+	ret = clk_pll14xx_ssc_mod_type(s, &conf->mod_type);
+	if (ret) {
+		pr_err("wrong fsl,ssc-modmethod property for %pOFn\n", np);
+		return ret;
+	}
+
+	pr_debug("%s: SSC %s settings: mod_freq: %d, mod_rate: %d: mod_method: %s [%d]\n",
+		__func__, pll_name, conf->mod_freq, conf->mod_rate, s, conf->mod_type);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(imx_clk_pll14xx_ssc_parse_dt);

diff --git a/drivers/clk/imx/clk.h b/drivers/clk/imx/clk.h
index 52055fda3058..edd28b78b115 100644
--- a/drivers/clk/imx/clk.h
+++ b/drivers/clk/imx/clk.h

@@ -69,6 +69,18 @@ struct imx_pll14xx_clk {
 	int flags;
 };
 
+enum imx_pll14xx_ssc_mod_type {
+	IMX_PLL14XX_SSC_DOWN_SPREAD,
+	IMX_PLL14XX_SSC_UP_SPREAD,
+	IMX_PLL14XX_SSC_CENTER_SPREAD,
+};
+
+struct imx_pll14xx_ssc {
+	unsigned int mod_freq;
+	unsigned int mod_rate;
+	enum imx_pll14xx_ssc_mod_type mod_type;
+};
+
 extern struct imx_pll14xx_clk imx_1416x_pll;
 extern struct imx_pll14xx_clk imx_1443x_pll;
 extern struct imx_pll14xx_clk imx_1443x_dram_pll;

@@ -494,4 +506,8 @@ struct clk_hw *imx_clk_gpr_mux(const char *name, const char *compatible,
 struct clk_hw *imx8m_anatop_get_clk_hw(int id);
 #endif
 
+void imx_clk_pll14xx_enable_ssc(struct clk_hw *hw, struct imx_pll14xx_ssc *conf);
+int imx_clk_pll14xx_ssc_parse_dt(struct device_node *np, const char *pll_name,
+				 struct imx_pll14xx_ssc *conf);
+
 #endif

-- 
2.43.0

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