i2c: mux: ltc4306: LTC4306 and LTC4305 I2C multiplexer/switch

This patch adds support for the Analog Devices / Linear Technology
LTC4306 and LTC4305 4/2 Channel I2C Bus Multiplexer/Switches.
The LTC4306 optionally provides two general purpose input/output pins
(GPIOs) that can be configured as logic inputs, opendrain outputs or
push-pull outputs via the generic GPIOLIB framework.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Peter Rosin <peda@axentia.se>

3 files changed, 334 insertions, 0 deletions

diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
index 10b3d17ae3ea..1e160fc37ecc 100644
--- a/drivers/i2c/muxes/Kconfig
+++ b/drivers/i2c/muxes/Kconfig
@@ -30,6 +30,17 @@ config I2C_MUX_GPIO
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-mux-gpio.
 
+config I2C_MUX_LTC4306
+	tristate "LTC LTC4306/5 I2C multiplexer"
+	select GPIOLIB
+	select REGMAP_I2C
+	help
+	  If you say yes here you get support for the Analog Devices
+	  LTC4306 or LTC4305 I2C mux/switch devices.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called i2c-mux-ltc4306.
+
 config I2C_MUX_PCA9541
 	tristate "NXP PCA9541 I2C Master Selector"
 	help
diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
index 9948fa45037f..ff7618cd5312 100644
--- a/drivers/i2c/muxes/Makefile
+++ b/drivers/i2c/muxes/Makefile
@@ -6,6 +6,7 @@ obj-$(CONFIG_I2C_ARB_GPIO_CHALLENGE)	+= i2c-arb-gpio-challenge.o
 obj-$(CONFIG_I2C_DEMUX_PINCTRL)		+= i2c-demux-pinctrl.o
 
 obj-$(CONFIG_I2C_MUX_GPIO)	+= i2c-mux-gpio.o
+obj-$(CONFIG_I2C_MUX_LTC4306)	+= i2c-mux-ltc4306.o
 obj-$(CONFIG_I2C_MUX_MLXCPLD)	+= i2c-mux-mlxcpld.o
 obj-$(CONFIG_I2C_MUX_PCA9541)	+= i2c-mux-pca9541.o
 obj-$(CONFIG_I2C_MUX_PCA954x)	+= i2c-mux-pca954x.o
diff --git a/drivers/i2c/muxes/i2c-mux-ltc4306.c b/drivers/i2c/muxes/i2c-mux-ltc4306.c
new file mode 100644
index 000000000000..311b1cced0c0
--- /dev/null
+++ b/drivers/i2c/muxes/i2c-mux-ltc4306.c
@@ -0,0 +1,322 @@
+/*
+ * Linear Technology LTC4306 and LTC4305 I2C multiplexer/switch
+ *
+ * Copyright (C) 2017 Analog Devices Inc.
+ *
+ * Licensed under the GPL-2.
+ *
+ * Based on: i2c-mux-pca954x.c
+ *
+ * Datasheet: http://cds.linear.com/docs/en/datasheet/4306.pdf
+ */
+
+#include <linux/gpio/consumer.h>
+#include <linux/gpio/driver.h>
+#include <linux/i2c-mux.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+#define LTC4305_MAX_NCHANS 2
+#define LTC4306_MAX_NCHANS 4
+
+#define LTC_REG_STATUS	0x0
+#define LTC_REG_CONFIG	0x1
+#define LTC_REG_MODE	0x2
+#define LTC_REG_SWITCH	0x3
+
+#define LTC_DOWNSTREAM_ACCL_EN	BIT(6)
+#define LTC_UPSTREAM_ACCL_EN	BIT(7)
+
+#define LTC_GPIO_ALL_INPUT	0xC0
+#define LTC_SWITCH_MASK		0xF0
+
+enum ltc_type {
+	ltc_4305,
+	ltc_4306,
+};
+
+struct chip_desc {
+	u8 nchans;
+	u8 num_gpios;
+};
+
+struct ltc4306 {
+	struct regmap *regmap;
+	struct gpio_chip gpiochip;
+	const struct chip_desc *chip;
+};
+
+static const struct chip_desc chips[] = {
+	[ltc_4305] = {
+		.nchans = LTC4305_MAX_NCHANS,
+	},
+	[ltc_4306] = {
+		.nchans = LTC4306_MAX_NCHANS,
+		.num_gpios = 2,
+	},
+};
+
+static bool ltc4306_is_volatile_reg(struct device *dev, unsigned int reg)
+{
+	return (reg == LTC_REG_CONFIG) ? true : false;
+}
+
+static const struct regmap_config ltc4306_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = LTC_REG_SWITCH,
+	.volatile_reg = ltc4306_is_volatile_reg,
+	.cache_type = REGCACHE_FLAT,
+};
+
+static int ltc4306_gpio_get(struct gpio_chip *chip, unsigned int offset)
+{
+	struct ltc4306 *data = gpiochip_get_data(chip);
+	unsigned int val;
+	int ret;
+
+	ret = regmap_read(data->regmap, LTC_REG_CONFIG, &val);
+	if (ret < 0)
+		return ret;
+
+	return !!(val & BIT(1 - offset));
+}
+
+static void ltc4306_gpio_set(struct gpio_chip *chip, unsigned int offset,
+			     int value)
+{
+	struct ltc4306 *data = gpiochip_get_data(chip);
+
+	regmap_update_bits(data->regmap, LTC_REG_CONFIG, BIT(5 - offset),
+			   value ? BIT(5 - offset) : 0);
+}
+
+static int ltc4306_gpio_get_direction(struct gpio_chip *chip,
+				      unsigned int offset)
+{
+	struct ltc4306 *data = gpiochip_get_data(chip);
+	unsigned int val;
+	int ret;
+
+	ret = regmap_read(data->regmap, LTC_REG_MODE, &val);
+	if (ret < 0)
+		return ret;
+
+	return !!(val & BIT(7 - offset));
+}
+
+static int ltc4306_gpio_direction_input(struct gpio_chip *chip,
+					unsigned int offset)
+{
+	struct ltc4306 *data = gpiochip_get_data(chip);
+
+	return regmap_update_bits(data->regmap, LTC_REG_MODE,
+				  BIT(7 - offset), BIT(7 - offset));
+}
+
+static int ltc4306_gpio_direction_output(struct gpio_chip *chip,
+					 unsigned int offset, int value)
+{
+	struct ltc4306 *data = gpiochip_get_data(chip);
+
+	ltc4306_gpio_set(chip, offset, value);
+	return regmap_update_bits(data->regmap, LTC_REG_MODE,
+				  BIT(7 - offset), 0);
+}
+
+static int ltc4306_gpio_set_config(struct gpio_chip *chip,
+				   unsigned int offset, unsigned long config)
+{
+	struct ltc4306 *data = gpiochip_get_data(chip);
+	unsigned int val;
+
+	switch (pinconf_to_config_param(config)) {
+	case PIN_CONFIG_DRIVE_OPEN_DRAIN:
+		val = 0;
+		break;
+	case PIN_CONFIG_DRIVE_PUSH_PULL:
+		val = BIT(4 - offset);
+		break;
+	default:
+		return -ENOTSUPP;
+	}
+
+	return regmap_update_bits(data->regmap, LTC_REG_MODE,
+				  BIT(4 - offset), val);
+}
+
+static int ltc4306_gpio_init(struct ltc4306 *data)
+{
+	struct device *dev = regmap_get_device(data->regmap);
+
+	if (!data->chip->num_gpios)
+		return 0;
+
+	data->gpiochip.label = dev_name(dev);
+	data->gpiochip.base = -1;
+	data->gpiochip.ngpio = data->chip->num_gpios;
+	data->gpiochip.parent = dev;
+	data->gpiochip.can_sleep = true;
+	data->gpiochip.get_direction = ltc4306_gpio_get_direction;
+	data->gpiochip.direction_input = ltc4306_gpio_direction_input;
+	data->gpiochip.direction_output = ltc4306_gpio_direction_output;
+	data->gpiochip.get = ltc4306_gpio_get;
+	data->gpiochip.set = ltc4306_gpio_set;
+	data->gpiochip.set_config = ltc4306_gpio_set_config;
+	data->gpiochip.owner = THIS_MODULE;
+
+	/* gpiolib assumes all GPIOs default input */
+	regmap_write(data->regmap, LTC_REG_MODE, LTC_GPIO_ALL_INPUT);
+
+	return devm_gpiochip_add_data(dev, &data->gpiochip, data);
+}
+
+static int ltc4306_select_mux(struct i2c_mux_core *muxc, u32 chan)
+{
+	struct ltc4306 *data = i2c_mux_priv(muxc);
+
+	return regmap_update_bits(data->regmap, LTC_REG_SWITCH,
+				  LTC_SWITCH_MASK, BIT(7 - chan));
+}
+
+static int ltc4306_deselect_mux(struct i2c_mux_core *muxc, u32 chan)
+{
+	struct ltc4306 *data = i2c_mux_priv(muxc);
+
+	return regmap_update_bits(data->regmap, LTC_REG_SWITCH,
+				  LTC_SWITCH_MASK, 0);
+}
+
+static const struct i2c_device_id ltc4306_id[] = {
+	{ "ltc4305", ltc_4305 },
+	{ "ltc4306", ltc_4306 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ltc4306_id);
+
+static const struct of_device_id ltc4306_of_match[] = {
+	{ .compatible = "lltc,ltc4305", .data = &chips[ltc_4305] },
+	{ .compatible = "lltc,ltc4306", .data = &chips[ltc_4306] },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ltc4306_of_match);
+
+static int ltc4306_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	struct i2c_adapter *adap = to_i2c_adapter(client->dev.parent);
+	const struct chip_desc *chip;
+	struct i2c_mux_core *muxc;
+	struct ltc4306 *data;
+	struct gpio_desc *gpio;
+	bool idle_disc;
+	unsigned int val = 0;
+	int num, ret;
+
+	chip = of_device_get_match_data(&client->dev);
+
+	if (!chip)
+		chip = &chips[id->driver_data];
+
+	idle_disc = device_property_read_bool(&client->dev,
+					      "i2c-mux-idle-disconnect");
+
+	muxc = i2c_mux_alloc(adap, &client->dev,
+			     chip->nchans, sizeof(*data),
+			     I2C_MUX_LOCKED, ltc4306_select_mux,
+			     idle_disc ? ltc4306_deselect_mux : NULL);
+	if (!muxc)
+		return -ENOMEM;
+	data = i2c_mux_priv(muxc);
+	data->chip = chip;
+
+	i2c_set_clientdata(client, muxc);
+
+	data->regmap = devm_regmap_init_i2c(client, &ltc4306_regmap_config);
+	if (IS_ERR(data->regmap)) {
+		ret = PTR_ERR(data->regmap);
+		dev_err(&client->dev, "Failed to allocate register map: %d\n",
+			ret);
+		return ret;
+	}
+
+	/* Reset and enable the mux if an enable GPIO is specified. */
+	gpio = devm_gpiod_get_optional(&client->dev, "enable", GPIOD_OUT_LOW);
+	if (IS_ERR(gpio))
+		return PTR_ERR(gpio);
+
+	if (gpio) {
+		udelay(1);
+		gpiod_set_value(gpio, 1);
+	}
+
+	/*
+	 * Write the mux register at addr to verify
+	 * that the mux is in fact present. This also
+	 * initializes the mux to disconnected state.
+	 */
+	if (regmap_write(data->regmap, LTC_REG_SWITCH, 0) < 0) {
+		dev_warn(&client->dev, "probe failed\n");
+		return -ENODEV;
+	}
+
+	if (device_property_read_bool(&client->dev,
+				      "ltc,downstream-accelerators-enable"))
+		val |= LTC_DOWNSTREAM_ACCL_EN;
+
+	if (device_property_read_bool(&client->dev,
+				      "ltc,upstream-accelerators-enable"))
+		val |= LTC_UPSTREAM_ACCL_EN;
+
+	if (regmap_write(data->regmap, LTC_REG_CONFIG, val) < 0)
+		return -ENODEV;
+
+	ret = ltc4306_gpio_init(data);
+	if (ret < 0)
+		return ret;
+
+	/* Now create an adapter for each channel */
+	for (num = 0; num < chip->nchans; num++) {
+		ret = i2c_mux_add_adapter(muxc, 0, num, 0);
+		if (ret) {
+			i2c_mux_del_adapters(muxc);
+			return ret;
+		}
+	}
+
+	dev_info(&client->dev,
+		 "registered %d multiplexed busses for I2C switch %s\n",
+		 num, client->name);
+
+	return 0;
+}
+
+static int ltc4306_remove(struct i2c_client *client)
+{
+	struct i2c_mux_core *muxc = i2c_get_clientdata(client);
+
+	i2c_mux_del_adapters(muxc);
+
+	return 0;
+}
+
+static struct i2c_driver ltc4306_driver = {
+	.driver		= {
+		.name	= "ltc4306",
+		.of_match_table = of_match_ptr(ltc4306_of_match),
+	},
+	.probe		= ltc4306_probe,
+	.remove		= ltc4306_remove,
+	.id_table	= ltc4306_id,
+};
+
+module_i2c_driver(ltc4306_driver);
+
+MODULE_AUTHOR("Michael Hennerich <michael.hennerich@analog.com>");
+MODULE_DESCRIPTION("Linear Technology LTC4306, LTC4305 I2C mux/switch driver");
+MODULE_LICENSE("GPL v2");