Add driver for the si514 clock generator chip

This patch adds the driver and devicetree documentation for the
Silicon Labs SI514 clock generator chip. This is an I2C controlled
oscillator capable of generating clock signals ranging from 100kHz
to 250MHz.

Signed-off-by: Mike Looijmans <[e-mail]>
[[e-mail]: Drop clk.h include, remove some casts]
Signed-off-by: Stephen Boyd <[e-mail]>

Documentation/devicetree/bindings/clock/silabs,si514.txt

···
+Binding for Silicon Labs 514 programmable I2C clock generator.
+
+Reference
+This binding uses the common clock binding[1]. Details about the device can be
+found in the datasheet[2].
+
+[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
+[2] Si514 datasheet
+    http://www.silabs.com/Support%20Documents/TechnicalDocs/si514.pdf
+
+Required properties:
+ - compatible: Shall be "silabs,si514"
+ - reg: I2C device address.
+ - #clock-cells: From common clock bindings: Shall be 0.
+
+Optional properties:
+ - clock-output-names: From common clock bindings. Recommended to be "si514".
+
+Example:
+	si514: clock-generator@55 {
+		reg = <0x55>;
+		#clock-cells = <0>;
+		compatible = "silabs,si514";
+	};

drivers/clk/Kconfig

···
 	  This driver supports Silicon Labs 5351A/B/C programmable clock
 	  generators.
 
+config COMMON_CLK_SI514
+	tristate "Clock driver for SiLabs 514 devices"
+	depends on I2C
+	depends on OF
+	select REGMAP_I2C
+	help
+	---help---
+	  This driver supports the Silicon Labs 514 programmable clock
+	  generator.
+
 config COMMON_CLK_SI570
 	tristate "Clock driver for SiLabs 570 and compatible devices"
 	depends on I2C

drivers/clk/Makefile

···
 obj-$(CONFIG_COMMON_CLK_RK808)		+= clk-rk808.o
 obj-$(CONFIG_COMMON_CLK_S2MPS11)	+= clk-s2mps11.o
 obj-$(CONFIG_COMMON_CLK_SI5351)		+= clk-si5351.o
+obj-$(CONFIG_COMMON_CLK_SI514)		+= clk-si514.o
 obj-$(CONFIG_COMMON_CLK_SI570)		+= clk-si570.o
 obj-$(CONFIG_COMMON_CLK_CDCE925)	+= clk-cdce925.o
 obj-$(CONFIG_ARCH_STM32)		+= clk-stm32f4.o

drivers/clk/clk-si514.c

···
+/*
+ * Driver for Silicon Labs Si514 Programmable Oscillator
+ *
+ * Copyright (C) 2015 Topic Embedded Products
+ *
+ * Author: Mike Looijmans <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+/* I2C registers */
+#define SI514_REG_LP		0
+#define SI514_REG_M_FRAC1	5
+#define SI514_REG_M_FRAC2	6
+#define SI514_REG_M_FRAC3	7
+#define SI514_REG_M_INT_FRAC	8
+#define SI514_REG_M_INT		9
+#define SI514_REG_HS_DIV	10
+#define SI514_REG_LS_HS_DIV	11
+#define SI514_REG_OE_STATE	14
+#define SI514_REG_RESET		128
+#define SI514_REG_CONTROL	132
+
+/* Register values */
+#define SI514_RESET_RST		BIT(7)
+
+#define SI514_CONTROL_FCAL	BIT(0)
+#define SI514_CONTROL_OE	BIT(2)
+
+#define SI514_MIN_FREQ	    100000U
+#define SI514_MAX_FREQ	 250000000U
+
+#define FXO		  31980000U
+
+#define FVCO_MIN	2080000000U
+#define FVCO_MAX	2500000000U
+
+#define HS_DIV_MAX	1022
+
+struct clk_si514 {
+	struct clk_hw hw;
+	struct regmap *regmap;
+	struct i2c_client *i2c_client;
+};
+#define to_clk_si514(_hw)	container_of(_hw, struct clk_si514, hw)
+
+/* Multiplier/divider settings */
+struct clk_si514_muldiv {
+	u32 m_frac;  /* 29-bit Fractional part of multiplier M */
+	u8 m_int; /* Integer part of multiplier M, 65..78 */
+	u8 ls_div_bits; /* 2nd divider, as 2^x */
+	u16 hs_div; /* 1st divider, must be even and 10<=x<=1022 */
+};
+
+/* Enables or disables the output driver */
+static int si514_enable_output(struct clk_si514 *data, bool enable)
+{
+	return regmap_update_bits(data->regmap, SI514_REG_CONTROL,
+		SI514_CONTROL_OE, enable ? SI514_CONTROL_OE : 0);
+}
+
+/* Retrieve clock multiplier and dividers from hardware */
+static int si514_get_muldiv(struct clk_si514 *data,
+	struct clk_si514_muldiv *settings)
+{
+	int err;
+	u8 reg[7];
+
+	err = regmap_bulk_read(data->regmap, SI514_REG_M_FRAC1,
+			reg, ARRAY_SIZE(reg));
+	if (err)
+		return err;
+
+	settings->m_frac = reg[0] | reg[1] << 8 | reg[2] << 16 |
+			   (reg[3] & 0x1F) << 24;
+	settings->m_int = (reg[4] & 0x3f) << 3 | reg[3] >> 5;
+	settings->ls_div_bits = (reg[6] >> 4) & 0x07;
+	settings->hs_div = (reg[6] & 0x03) << 8 | reg[5];
+	return 0;
+}
+
+static int si514_set_muldiv(struct clk_si514 *data,
+	struct clk_si514_muldiv *settings)
+{
+	u8 lp;
+	u8 reg[7];
+	int err;
+
+	/* Calculate LP1/LP2 according to table 13 in the datasheet */
+	/* 65.259980246 */
+	if (settings->m_int < 65 ||
+		(settings->m_int == 65 && settings->m_frac <= 139575831))
+		lp = 0x22;
+	/* 67.859763463 */
+	else if (settings->m_int < 67 ||
+		(settings->m_int == 67 && settings->m_frac <= 461581994))
+		lp = 0x23;
+	/* 72.937624981 */
+	else if (settings->m_int < 72 ||
+		(settings->m_int == 72 && settings->m_frac <= 503383578))
+		lp = 0x33;
+	/* 75.843265046 */
+	else if (settings->m_int < 75 ||
+		(settings->m_int == 75 && settings->m_frac <= 452724474))
+		lp = 0x34;
+	else
+		lp = 0x44;
+
+	err = regmap_write(data->regmap, SI514_REG_LP, lp);
+	if (err < 0)
+		return err;
+
+	reg[0] = settings->m_frac;
+	reg[1] = settings->m_frac >> 8;
+	reg[2] = settings->m_frac >> 16;
+	reg[3] = settings->m_frac >> 24 | settings->m_int << 5;
+	reg[4] = settings->m_int >> 3;
+	reg[5] = settings->hs_div;
+	reg[6] = (settings->hs_div >> 8) | (settings->ls_div_bits << 4);
+
+	err = regmap_bulk_write(data->regmap, SI514_REG_HS_DIV, reg + 5, 2);
+	if (err < 0)
+		return err;
+	/*
+	 * Writing to SI514_REG_M_INT_FRAC triggers the clock change, so that
+	 * must be written last
+	 */
+	return regmap_bulk_write(data->regmap, SI514_REG_M_FRAC1, reg, 5);
+}
+
+/* Calculate divider settings for a given frequency */
+static int si514_calc_muldiv(struct clk_si514_muldiv *settings,
+	unsigned long frequency)
+{
+	u64 m;
+	u32 ls_freq;
+	u32 tmp;
+	u8 res;
+
+	if ((frequency < SI514_MIN_FREQ) || (frequency > SI514_MAX_FREQ))
+		return -EINVAL;
+
+	/* Determine the minimum value of LS_DIV and resulting target freq. */
+	ls_freq = frequency;
+	if (frequency >= (FVCO_MIN / HS_DIV_MAX))
+		settings->ls_div_bits = 0;
+	else {
+		res = 1;
+		tmp = 2 * HS_DIV_MAX;
+		while (tmp <= (HS_DIV_MAX * 32)) {
+			if ((frequency * tmp) >= FVCO_MIN)
+				break;
+			++res;
+			tmp <<= 1;
+		}
+		settings->ls_div_bits = res;
+		ls_freq = frequency << res;
+	}
+
+	/* Determine minimum HS_DIV, round up to even number */
+	settings->hs_div = DIV_ROUND_UP(FVCO_MIN >> 1, ls_freq) << 1;
+
+	/* M = LS_DIV x HS_DIV x frequency / F_XO (in fixed-point) */
+	m = ((u64)(ls_freq * settings->hs_div) << 29) + (FXO / 2);
+	do_div(m, FXO);
+	settings->m_frac = (u32)m & (BIT(29) - 1);
+	settings->m_int = (u32)(m >> 29);
+
+	return 0;
+}
+
+/* Calculate resulting frequency given the register settings */
+static unsigned long si514_calc_rate(struct clk_si514_muldiv *settings)
+{
+	u64 m = settings->m_frac | ((u64)settings->m_int << 29);
+	u32 d = settings->hs_div * BIT(settings->ls_div_bits);
+
+	return ((u32)(((m * FXO) + (FXO / 2)) >> 29)) / d;
+}
+
+static unsigned long si514_recalc_rate(struct clk_hw *hw,
+		unsigned long parent_rate)
+{
+	struct clk_si514 *data = to_clk_si514(hw);
+	struct clk_si514_muldiv settings;
+	int err;
+
+	err = si514_get_muldiv(data, &settings);
+	if (err) {
+		dev_err(&data->i2c_client->dev, "unable to retrieve settings\n");
+		return 0;
+	}
+
+	return si514_calc_rate(&settings);
+}
+
+static long si514_round_rate(struct clk_hw *hw, unsigned long rate,
+		unsigned long *parent_rate)
+{
+	struct clk_si514_muldiv settings;
+	int err;
+
+	if (!rate)
+		return 0;
+
+	err = si514_calc_muldiv(&settings, rate);
+	if (err)
+		return err;
+
+	return si514_calc_rate(&settings);
+}
+
+/*
+ * Update output frequency for big frequency changes (> 1000 ppm).
+ * The chip supports <1000ppm changes "on the fly", we haven't implemented
+ * that here.
+ */
+static int si514_set_rate(struct clk_hw *hw, unsigned long rate,
+		unsigned long parent_rate)
+{
+	struct clk_si514 *data = to_clk_si514(hw);
+	struct clk_si514_muldiv settings;
+	int err;
+
+	err = si514_calc_muldiv(&settings, rate);
+	if (err)
+		return err;
+
+	si514_enable_output(data, false);
+
+	err = si514_set_muldiv(data, &settings);
+	if (err < 0)
+		return err; /* Undefined state now, best to leave disabled */
+
+	/* Trigger calibration */
+	err = regmap_write(data->regmap, SI514_REG_CONTROL, SI514_CONTROL_FCAL);
+	if (err < 0)
+		return err;
+
+	/* Applying a new frequency can take up to 10ms */
+	usleep_range(10000, 12000);
+
+	si514_enable_output(data, true);
+
+	return err;
+}
+
+static const struct clk_ops si514_clk_ops = {
+	.recalc_rate = si514_recalc_rate,
+	.round_rate = si514_round_rate,
+	.set_rate = si514_set_rate,
+};
+
+static bool si514_regmap_is_volatile(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case SI514_REG_CONTROL:
+	case SI514_REG_RESET:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static bool si514_regmap_is_writeable(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case SI514_REG_LP:
+	case SI514_REG_M_FRAC1 ... SI514_REG_LS_HS_DIV:
+	case SI514_REG_OE_STATE:
+	case SI514_REG_RESET:
+	case SI514_REG_CONTROL:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static const struct regmap_config si514_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.cache_type = REGCACHE_RBTREE,
+	.max_register = SI514_REG_CONTROL,
+	.writeable_reg = si514_regmap_is_writeable,
+	.volatile_reg = si514_regmap_is_volatile,
+};
+
+static int si514_probe(struct i2c_client *client,
+		const struct i2c_device_id *id)
+{
+	struct clk_si514 *data;
+	struct clk_init_data init;
+	struct clk *clk;
+	int err;
+
+	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	init.ops = &si514_clk_ops;
+	init.flags = CLK_IS_ROOT;
+	init.num_parents = 0;
+	data->hw.init = &init;
+	data->i2c_client = client;
+
+	if (of_property_read_string(client->dev.of_node, "clock-output-names",
+			&init.name))
+		init.name = client->dev.of_node->name;
+
+	data->regmap = devm_regmap_init_i2c(client, &si514_regmap_config);
+	if (IS_ERR(data->regmap)) {
+		dev_err(&client->dev, "failed to allocate register map\n");
+		return PTR_ERR(data->regmap);
+	}
+
+	i2c_set_clientdata(client, data);
+
+	clk = devm_clk_register(&client->dev, &data->hw);
+	if (IS_ERR(clk)) {
+		dev_err(&client->dev, "clock registration failed\n");
+		return PTR_ERR(clk);
+	}
+	err = of_clk_add_provider(client->dev.of_node, of_clk_src_simple_get,
+			clk);
+	if (err) {
+		dev_err(&client->dev, "unable to add clk provider\n");
+		return err;
+	}
+
+	return 0;
+}
+
+static int si514_remove(struct i2c_client *client)
+{
+	of_clk_del_provider(client->dev.of_node);
+	return 0;
+}
+
+static const struct i2c_device_id si514_id[] = {
+	{ "si514", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, si514_id);
+
+static const struct of_device_id clk_si514_of_match[] = {
+	{ .compatible = "silabs,si514" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, clk_si514_of_match);
+
+static struct i2c_driver si514_driver = {
+	.driver = {
+		.name = "si514",
+		.of_match_table = clk_si514_of_match,
+	},
+	.probe		= si514_probe,
+	.remove		= si514_remove,
+	.id_table	= si514_id,
+};
+module_i2c_driver(si514_driver);
+
+MODULE_AUTHOR("Mike Looijmans <[e-mail]>");
+MODULE_DESCRIPTION("Si514 driver");
+MODULE_LICENSE("GPL");