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Subject[PATCH v2] i2c/muxes/i2c-mux-ltc4306: LTC4306 and LTC4305 I2C multiplexer/switch
Date
From: Michael Hennerich <michael.hennerich@analog.com>

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>

---

Changes since v1:

- Sort makefile entries
- Sort driver includes
- Use proper defines
- Miscellaneous coding style fixups
- Rename mux select callback
- Revise i2c-mux-idle-disconnect handling
- Add ENABLE GPIO handling on error and device removal.
- Remove surplus of_match_device call.
---
.../devicetree/bindings/i2c/i2c-mux-ltc4306.txt | 61 ++++
MAINTAINERS | 8 +
drivers/i2c/muxes/Kconfig | 10 +
drivers/i2c/muxes/Makefile | 1 +
drivers/i2c/muxes/i2c-mux-ltc4306.c | 367 +++++++++++++++++++++
5 files changed, 447 insertions(+)
create mode 100644 Documentation/devicetree/bindings/i2c/i2c-mux-ltc4306.txt
create mode 100644 drivers/i2c/muxes/i2c-mux-ltc4306.c

diff --git a/Documentation/devicetree/bindings/i2c/i2c-mux-ltc4306.txt b/Documentation/devicetree/bindings/i2c/i2c-mux-ltc4306.txt
new file mode 100644
index 0000000..1e98c6b
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/i2c-mux-ltc4306.txt
@@ -0,0 +1,61 @@
+* Linear Technology / Analog Devices I2C bus switch
+
+Required Properties:
+
+ - compatible: Must contain one of the following.
+ "lltc,ltc4305", "lltc,ltc4306"
+ - reg: The I2C address of the device.
+
+ The following required properties are defined externally:
+
+ - Standard I2C mux properties. See i2c-mux.txt in this directory.
+ - I2C child bus nodes. See i2c-mux.txt in this directory.
+
+Optional Properties:
+
+ - enable-gpios: Reference to the GPIO connected to the enable input.
+ - i2c-mux-idle-disconnect: Boolean; if defined, forces mux to disconnect all
+ children in idle state. This is necessary for example, if there are several
+ multiplexers on the bus and the devices behind them use same I2C addresses.
+ - gpio-controller: Marks the device node as a GPIO Controller.
+ - #gpio-cells: Should be two. The first cell is the pin number and
+ the second cell is used to specify flags.
+ See ../gpio/gpio.txt for more information.
+ - ltc,downstream-accelerators-enable: Enables the rise time accelerators
+ on the downstream port.
+ - ltc,upstream-accelerators-enable: Enables the rise time accelerators
+ on the upstream port.
+
+Example:
+
+ ltc4306: i2c-mux@4a {
+ compatible = "lltc,ltc4306";
+ #address-cells = <1>;
+ #size-cells = <0>;
+ reg = <0x4a>;
+
+ gpio-controller;
+ #gpio-cells = <2>;
+
+ i2c@0 {
+ #address-cells = <1>;
+ #size-cells = <0>;
+ reg = <0>;
+
+ eeprom@50 {
+ compatible = "at,24c02";
+ reg = <0x50>;
+ };
+ };
+
+ i2c@1 {
+ #address-cells = <1>;
+ #size-cells = <0>;
+ reg = <1>;
+
+ eeprom@50 {
+ compatible = "at,24c02";
+ reg = <0x50>;
+ };
+ };
+ };
diff --git a/MAINTAINERS b/MAINTAINERS
index c776906..9a27a19 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7698,6 +7698,14 @@ S: Maintained
F: Documentation/hwmon/ltc4261
F: drivers/hwmon/ltc4261.c

+LTC4306 I2C MULTIPLEXER DRIVER
+M: Michael Hennerich <michael.hennerich@analog.com>
+W: http://ez.analog.com/community/linux-device-drivers
+L: linux-i2c@vger.kernel.org
+S: Supported
+F: drivers/i2c/muxes/i2c-mux-ltc4306.c
+F: Documentation/devicetree/bindings/i2c/i2c-mux-ltc4306.txt
+
LTP (Linux Test Project)
M: Mike Frysinger <vapier@gentoo.org>
M: Cyril Hrubis <chrubis@suse.cz>
diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
index 10b3d17..f501b3b 100644
--- a/drivers/i2c/muxes/Kconfig
+++ b/drivers/i2c/muxes/Kconfig
@@ -30,6 +30,16 @@ 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
+ help
+ If you say yes here you get support for the LTC 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 9948fa4..ff7618c 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 0000000..c15a8a4
--- /dev/null
+++ b/drivers/i2c/muxes/i2c-mux-ltc4306.c
@@ -0,0 +1,367 @@
+/*
+ * 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/device.h>
+#include <linux/gpio.h>
+#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/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
+
+enum ltc_type {
+ ltc_4305,
+ ltc_4306,
+};
+
+struct chip_desc {
+ u8 nchans;
+ u8 num_gpios;
+};
+
+struct ltc4306 {
+ struct i2c_client *client;
+ struct gpio_desc *en_gpio;
+ struct gpio_chip gpiochip;
+ const struct chip_desc *chip;
+ u8 regs[LTC_REG_SWITCH + 1];
+};
+
+/* Provide specs for the PCA954x types we know about */
+static const struct chip_desc chips[] = {
+ [ltc_4305] = {
+ .nchans = LTC4305_MAX_NCHANS,
+ },
+ [ltc_4306] = {
+ .nchans = LTC4306_MAX_NCHANS,
+ .num_gpios = 2,
+ },
+};
+
+static int ltc4306_gpio_get(struct gpio_chip *chip, unsigned int offset)
+{
+ struct ltc4306 *data = gpiochip_get_data(chip);
+ int ret = 0;
+
+ if (gpiochip_line_is_open_drain(chip, offset) ||
+ (data->regs[LTC_REG_MODE] & BIT(7 - offset))) {
+ /* Open Drain or Input */
+ ret = i2c_smbus_read_byte_data(data->client, LTC_REG_CONFIG);
+ if (ret < 0)
+ return ret;
+
+ return !!(ret & BIT(1 - offset));
+ } else {
+ return !!(data->regs[LTC_REG_CONFIG] & BIT(5 - offset));
+ }
+}
+
+static void ltc4306_gpio_set(struct gpio_chip *chip, unsigned int offset,
+ int value)
+{
+ struct ltc4306 *data = gpiochip_get_data(chip);
+
+ if (value)
+ data->regs[LTC_REG_CONFIG] |= BIT(5 - offset);
+ else
+ data->regs[LTC_REG_CONFIG] &= ~BIT(5 - offset);
+
+ i2c_smbus_write_byte_data(data->client, LTC_REG_CONFIG,
+ data->regs[LTC_REG_CONFIG]);
+}
+
+static int ltc4306_gpio_direction_input(struct gpio_chip *chip,
+ unsigned int offset)
+{
+ struct ltc4306 *data = gpiochip_get_data(chip);
+
+ data->regs[LTC_REG_MODE] |= BIT(7 - offset);
+
+ return i2c_smbus_write_byte_data(data->client, LTC_REG_MODE,
+ data->regs[LTC_REG_MODE]);
+}
+
+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);
+ data->regs[LTC_REG_MODE] &= ~BIT(7 - offset);
+
+ return i2c_smbus_write_byte_data(data->client, LTC_REG_MODE,
+ data->regs[LTC_REG_MODE]);
+}
+
+static int ltc4306_gpio_set_config(struct gpio_chip *chip,
+ unsigned int offset, unsigned long config)
+{
+ struct ltc4306 *data = gpiochip_get_data(chip);
+
+ switch (pinconf_to_config_param(config)) {
+ case PIN_CONFIG_DRIVE_OPEN_DRAIN:
+ data->regs[LTC_REG_MODE] &= ~BIT(4 - offset);
+ break;
+ case PIN_CONFIG_DRIVE_PUSH_PULL:
+ data->regs[LTC_REG_MODE] |= BIT(4 - offset);
+ break;
+ default:
+ return -ENOTSUPP;
+ }
+
+ return i2c_smbus_write_byte_data(data->client, LTC_REG_MODE,
+ data->regs[LTC_REG_MODE]);
+}
+
+static int ltc4306_gpio_init(struct ltc4306 *data)
+{
+ if (!data->chip->num_gpios)
+ return 0;
+
+ data->gpiochip.label = dev_name(&data->client->dev);
+ data->gpiochip.base = -1;
+ data->gpiochip.ngpio = data->chip->num_gpios;
+ data->gpiochip.parent = &data->client->dev;
+ data->gpiochip.can_sleep = true;
+ 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 */
+ data->regs[LTC_REG_MODE] |= LTC_GPIO_ALL_INPUT;
+ i2c_smbus_write_byte_data(data->client, LTC_REG_MODE,
+ data->regs[LTC_REG_MODE]);
+
+ return devm_gpiochip_add_data(&data->client->dev,
+ &data->gpiochip, data);
+}
+
+/*
+ * Write to chip register. Don't use i2c_transfer()/i2c_smbus_xfer()
+ * as they will try to lock the adapter a second time.
+ */
+static int ltc4306_reg_write(struct i2c_adapter *adap,
+ struct i2c_client *client, u8 reg, u8 val)
+{
+ int ret;
+
+ if (adap->algo->master_xfer) {
+ struct i2c_msg msg;
+ char buf[2];
+
+ msg.addr = client->addr;
+ msg.flags = 0;
+ msg.len = 2;
+ buf[0] = reg;
+ buf[1] = val;
+ msg.buf = buf;
+ ret = __i2c_transfer(adap, &msg, 1);
+ } else {
+ union i2c_smbus_data data;
+
+ data.byte = val;
+ ret = adap->algo->smbus_xfer(adap, client->addr,
+ client->flags,
+ I2C_SMBUS_WRITE,
+ reg,
+ I2C_SMBUS_BYTE_DATA, &data);
+ }
+
+ return ret;
+}
+
+static int ltc4306_select_mux(struct i2c_mux_core *muxc, u32 chan)
+{
+ struct ltc4306 *data = i2c_mux_priv(muxc);
+ struct i2c_client *client = data->client;
+ u8 regval;
+ int ret = 0;
+
+ regval = BIT(7 - chan);
+
+ /* Only select the channel if its different from the last channel */
+ if (data->regs[LTC_REG_SWITCH] != regval) {
+ ret = ltc4306_reg_write(muxc->parent, client,
+ LTC_REG_SWITCH, regval);
+ data->regs[LTC_REG_SWITCH] = ret < 0 ? 0 : regval;
+ }
+
+ return ret;
+}
+
+static int ltc4306_deselect_mux(struct i2c_mux_core *muxc, u32 chan)
+{
+ struct ltc4306 *data = i2c_mux_priv(muxc);
+ struct i2c_client *client = data->client;
+
+ /* Deselect all channels */
+ data->regs[LTC_REG_SWITCH] = 0;
+
+ return ltc4306_reg_write(muxc->parent, client,
+ LTC_REG_SWITCH, data->regs[LTC_REG_SWITCH]);
+}
+
+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);
+ struct device_node *of_node = client->dev.of_node;
+ bool idle_disconnect_dt = false;
+ struct i2c_mux_core *muxc;
+ struct ltc4306 *data;
+ int num, ret;
+
+ if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_BYTE_DATA))
+ return -ENODEV;
+
+ if (of_node) {
+ idle_disconnect_dt =
+ of_property_read_bool(of_node,
+ "i2c-mux-idle-disconnect");
+ }
+
+ muxc = i2c_mux_alloc(adap, &client->dev,
+ LTC4306_MAX_NCHANS, sizeof(*data), 0,
+ ltc4306_select_mux, idle_disconnect_dt ?
+ ltc4306_deselect_mux : NULL);
+ if (!muxc)
+ return -ENOMEM;
+ data = i2c_mux_priv(muxc);
+
+ i2c_set_clientdata(client, muxc);
+ data->client = client;
+
+ /* Enable the mux if an enable GPIO is specified. */
+ data->en_gpio = devm_gpiod_get_optional(&client->dev, "enable",
+ GPIOD_OUT_HIGH);
+ if (IS_ERR(data->en_gpio))
+ return PTR_ERR(data->en_gpio);
+
+ /*
+ * Write the mux register at addr to verify
+ * that the mux is in fact present. This also
+ * initializes the mux to disconnected state.
+ */
+ if (i2c_smbus_write_byte_data(client, LTC_REG_SWITCH, 0) < 0) {
+ dev_warn(&client->dev, "probe failed\n");
+ ret = -ENODEV;
+ goto gpio_default;
+ }
+
+ if (of_node) {
+ data->chip = of_device_get_match_data(&client->dev);
+
+ if (of_property_read_bool(of_node,
+ "ltc,downstream-accelerators-enable"))
+ data->regs[LTC_REG_CONFIG] |= LTC_DOWNSTREAM_ACCL_EN;
+
+ if (of_property_read_bool(of_node,
+ "ltc,upstream-accelerators-enable"))
+ data->regs[LTC_REG_CONFIG] |= LTC_UPSTREAM_ACCL_EN;
+
+ if (i2c_smbus_write_byte_data(client, LTC_REG_CONFIG,
+ data->regs[LTC_REG_CONFIG]) < 0) {
+ dev_warn(&client->dev, "probe failed\n");
+ ret = -ENODEV;
+ goto gpio_default;
+ }
+ } else {
+ data->chip = &chips[id->driver_data];
+ }
+
+ ret = ltc4306_gpio_init(data);
+ if (ret < 0)
+ goto gpio_default;
+
+ /* Now create an adapter for each channel */
+ for (num = 0; num < data->chip->nchans; num++) {
+ ret = i2c_mux_add_adapter(muxc, 0, num, 0);
+ if (ret) {
+ dev_err(&client->dev,
+ "failed to register multiplexed adapter %d\n",
+ num);
+ goto add_adapter_failed;
+ }
+ }
+
+ dev_info(&client->dev,
+ "registered %d multiplexed busses for I2C switch %s\n",
+ num, client->name);
+
+ return 0;
+
+add_adapter_failed:
+ i2c_mux_del_adapters(muxc);
+gpio_default:
+ gpiod_direction_input(data->en_gpio);
+ return ret;
+}
+
+static int ltc4306_remove(struct i2c_client *client)
+{
+ struct i2c_mux_core *muxc = i2c_get_clientdata(client);
+ struct ltc4306 *data = i2c_mux_priv(muxc);
+
+ i2c_mux_del_adapters(muxc);
+ gpiod_direction_input(data->en_gpio);
+
+ 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");
--
2.7.4
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