clk: imx: Add fractional PLL output clock

This is a new fractional clock type introduced on i.MX8.

The description of this fractional clock can be found here:

https://www.nxp.com/docs/en/reference-manual/IMX8MDQLQRM.pdf#page=834

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Abel Vesa <abel.vesa@nxp.com>
Reviewed-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/imx/Makefile

@@ -7,6 +7,7 @@ obj-y += \
 	clk-cpu.o \
 	clk-fixup-div.o \
 	clk-fixup-mux.o \
+	clk-frac-pll.o \
 	clk-gate-exclusive.o \
 	clk-gate2.o \
 	clk-pllv1.o \

drivers/clk/imx/clk-frac-pll.c

@@ -0,0 +1,232 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2018 NXP.
+ *
+ * This driver supports the fractional plls found in the imx8m SOCs
+ *
+ * Documentation for this fractional pll can be found at:
+ *   https://www.nxp.com/docs/en/reference-manual/IMX8MDQLQRM.pdf#page=834
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/err.h>
+#include <linux/iopoll.h>
+#include <linux/slab.h>
+#include <linux/bitfield.h>
+
+#include "clk.h"
+
+#define PLL_CFG0		0x0
+#define PLL_CFG1		0x4
+
+#define PLL_LOCK_STATUS		BIT(31)
+#define PLL_PD_MASK		BIT(19)
+#define PLL_BYPASS_MASK		BIT(14)
+#define PLL_NEWDIV_VAL		BIT(12)
+#define PLL_NEWDIV_ACK		BIT(11)
+#define PLL_FRAC_DIV_MASK	GENMASK(30, 7)
+#define PLL_INT_DIV_MASK	GENMASK(6, 0)
+#define PLL_OUTPUT_DIV_MASK	GENMASK(4, 0)
+#define PLL_FRAC_DENOM		0x1000000
+
+#define PLL_FRAC_LOCK_TIMEOUT	10000
+#define PLL_FRAC_ACK_TIMEOUT	500000
+
+struct clk_frac_pll {
+	struct clk_hw	hw;
+	void __iomem	*base;
+};
+
+#define to_clk_frac_pll(_hw) container_of(_hw, struct clk_frac_pll, hw)
+
+static int clk_wait_lock(struct clk_frac_pll *pll)
+{
+	u32 val;
+
+	return readl_poll_timeout(pll->base, val, val & PLL_LOCK_STATUS, 0,
+					PLL_FRAC_LOCK_TIMEOUT);
+}
+
+static int clk_wait_ack(struct clk_frac_pll *pll)
+{
+	u32 val;
+
+	/* return directly if the pll is in powerdown or in bypass */
+	if (readl_relaxed(pll->base) & (PLL_PD_MASK | PLL_BYPASS_MASK))
+		return 0;
+
+	/* Wait for the pll's divfi and divff to be reloaded */
+	return readl_poll_timeout(pll->base, val, val & PLL_NEWDIV_ACK, 0,
+					PLL_FRAC_ACK_TIMEOUT);
+}
+
+static int clk_pll_prepare(struct clk_hw *hw)
+{
+	struct clk_frac_pll *pll = to_clk_frac_pll(hw);
+	u32 val;
+
+	val = readl_relaxed(pll->base + PLL_CFG0);
+	val &= ~PLL_PD_MASK;
+	writel_relaxed(val, pll->base + PLL_CFG0);
+
+	return clk_wait_lock(pll);
+}
+
+static void clk_pll_unprepare(struct clk_hw *hw)
+{
+	struct clk_frac_pll *pll = to_clk_frac_pll(hw);
+	u32 val;
+
+	val = readl_relaxed(pll->base + PLL_CFG0);
+	val |= PLL_PD_MASK;
+	writel_relaxed(val, pll->base + PLL_CFG0);
+}
+
+static int clk_pll_is_prepared(struct clk_hw *hw)
+{
+	struct clk_frac_pll *pll = to_clk_frac_pll(hw);
+	u32 val;
+
+	val = readl_relaxed(pll->base + PLL_CFG0);
+	return (val & PLL_PD_MASK) ? 0 : 1;
+}
+
+static unsigned long clk_pll_recalc_rate(struct clk_hw *hw,
+					 unsigned long parent_rate)
+{
+	struct clk_frac_pll *pll = to_clk_frac_pll(hw);
+	u32 val, divff, divfi, divq;
+	u64 temp64 = parent_rate;
+	u64 rate;
+
+	val = readl_relaxed(pll->base + PLL_CFG0);
+	divq = (FIELD_GET(PLL_OUTPUT_DIV_MASK, val) + 1) * 2;
+	val = readl_relaxed(pll->base + PLL_CFG1);
+	divff = FIELD_GET(PLL_FRAC_DIV_MASK, val);
+	divfi = FIELD_GET(PLL_INT_DIV_MASK, val);
+
+	temp64 *= 8;
+	temp64 *= divff;
+	do_div(temp64, PLL_FRAC_DENOM);
+	do_div(temp64, divq);
+
+	rate = parent_rate * 8 * (divfi + 1);
+	do_div(rate, divq);
+	rate += temp64;
+
+	return rate;
+}
+
+static long clk_pll_round_rate(struct clk_hw *hw, unsigned long rate,
+			       unsigned long *prate)
+{
+	u64 parent_rate = *prate;
+	u32 divff, divfi;
+	u64 temp64;
+
+	parent_rate *= 8;
+	rate *= 2;
+	temp64 = rate;
+	do_div(temp64, parent_rate);
+	divfi = temp64;
+	temp64 = rate - divfi * parent_rate;
+	temp64 *= PLL_FRAC_DENOM;
+	do_div(temp64, parent_rate);
+	divff = temp64;
+
+	temp64 = parent_rate;
+	temp64 *= divff;
+	do_div(temp64, PLL_FRAC_DENOM);
+
+	rate = parent_rate * divfi + temp64;
+
+	return rate / 2;
+}
+
+/*
+ * To simplify the clock calculation, we can keep the 'PLL_OUTPUT_VAL' at zero
+ * (means the PLL output will be divided by 2). So the PLL output can use
+ * the below formula:
+ * pllout = parent_rate * 8 / 2 * DIVF_VAL;
+ * where DIVF_VAL = 1 + DIVFI + DIVFF / 2^24.
+ */
+static int clk_pll_set_rate(struct clk_hw *hw, unsigned long rate,
+			    unsigned long parent_rate)
+{
+	struct clk_frac_pll *pll = to_clk_frac_pll(hw);
+	u32 val, divfi, divff;
+	u64 temp64 = parent_rate;
+	int ret;
+
+	parent_rate *= 8;
+	rate *= 2;
+	divfi = rate / parent_rate;
+	temp64 *= rate - divfi;
+	temp64 *= PLL_FRAC_DENOM;
+	do_div(temp64, parent_rate);
+	divff = temp64;
+
+	val = readl_relaxed(pll->base + PLL_CFG1);
+	val &= ~(PLL_FRAC_DIV_MASK | PLL_INT_DIV_MASK);
+	val |= (divff << 7) | (divfi - 1);
+	writel_relaxed(val, pll->base + PLL_CFG1);
+
+	val = readl_relaxed(pll->base + PLL_CFG0);
+	val &= ~0x1f;
+	writel_relaxed(val, pll->base + PLL_CFG0);
+
+	/* Set the NEV_DIV_VAL to reload the DIVFI and DIVFF */
+	val = readl_relaxed(pll->base + PLL_CFG0);
+	val |= PLL_NEWDIV_VAL;
+	writel_relaxed(val, pll->base + PLL_CFG0);
+
+	ret = clk_wait_ack(pll);
+
+	/* clear the NEV_DIV_VAL */
+	val = readl_relaxed(pll->base + PLL_CFG0);
+	val &= ~PLL_NEWDIV_VAL;
+	writel_relaxed(val, pll->base + PLL_CFG0);
+
+	return ret;
+}
+
+static const struct clk_ops clk_frac_pll_ops = {
+	.prepare	= clk_pll_prepare,
+	.unprepare	= clk_pll_unprepare,
+	.is_prepared	= clk_pll_is_prepared,
+	.recalc_rate	= clk_pll_recalc_rate,
+	.round_rate	= clk_pll_round_rate,
+	.set_rate	= clk_pll_set_rate,
+};
+
+struct clk *imx_clk_frac_pll(const char *name, const char *parent_name,
+			     void __iomem *base)
+{
+	struct clk_init_data init;
+	struct clk_frac_pll *pll;
+	struct clk_hw *hw;
+	int ret;
+
+	pll = kzalloc(sizeof(*pll), GFP_KERNEL);
+	if (!pll)
+		return ERR_PTR(-ENOMEM);
+
+	init.name = name;
+	init.ops = &clk_frac_pll_ops;
+	init.flags = 0;
+	init.parent_names = &parent_name;
+	init.num_parents = 1;
+
+	pll->base = base;
+	pll->hw.init = &init;
+
+	hw = &pll->hw;
+
+	ret = clk_hw_register(NULL, hw);
+	if (ret) {
+		kfree(pll);
+		return ERR_PTR(ret);
+	}
+
+	return hw->clk;
+}

drivers/clk/imx/clk.h

@@ -27,6 +27,9 @@ struct clk *imx_clk_pllv1(enum imx_pllv1_type type, const char *name,
 struct clk *imx_clk_pllv2(const char *name, const char *parent,
 		void __iomem *base);
 
+struct clk *imx_clk_frac_pll(const char *name, const char *parent_name,
+			     void __iomem *base);
+
 enum imx_pllv3_type {
 	IMX_PLLV3_GENERIC,
 	IMX_PLLV3_SYS,