driver: i2c: Add TCA9546a I2C switch driver

The driver only support use case where the channels are used in mutual
exclusion.
Origin: Original

Signed-off-by: Guillaume Lager <g.lager@innoseis.com>

drivers/i2c/i2c_tca9546a.c

@@ -0,0 +1,168 @@
+/*
+ * Copyright (c) 2020 Innoseis BV
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#define DT_DRV_COMPAT ti_tca9546a
+
+#include <zephyr.h>
+#include <device.h>
+#include <devicetree.h>
+#include <drivers/i2c.h>
+#include <logging/log.h>
+#include <stdint.h>
+
+LOG_MODULE_REGISTER(tca9546a, CONFIG_I2C_LOG_LEVEL);
+
+#define MAX_CHANNEL_MASK BIT_MASK(4)
+
+struct tca9546a_root_config {
+	const struct device *bus;
+	uint16_t slave_addr;
+};
+
+struct tca9546a_root_data {
+	struct k_mutex lock;
+	uint8_t selected_chan;
+};
+
+struct tca9546a_channel_config {
+	const struct device *root;
+	uint8_t chan_mask;
+};
+
+static inline struct tca9546a_root_data *
+get_root_data_from_channel(const struct device *dev)
+{
+	const struct tca9546a_channel_config *channel_config = dev->config;
+
+	return channel_config->root->data;
+}
+
+static inline const struct tca9546a_root_config *
+get_root_config_from_channel(const struct device *dev)
+{
+	const struct tca9546a_channel_config *channel_config = dev->config;
+
+	return channel_config->root->config;
+}
+
+static int tca9546a_configure(const struct device *dev, uint32_t dev_config)
+{
+	const struct tca9546a_root_config *cfg = get_root_config_from_channel(
+		dev);
+
+	return i2c_configure(cfg->bus, dev_config);
+}
+
+static int tca9546a_set_channel(const struct device *dev, uint8_t select_mask)
+{
+	int res = 0;
+	struct tca9546a_root_data *data = dev->data;
+	const struct tca9546a_root_config *cfg = dev->config;
+
+	if (data->selected_chan != select_mask) {
+		res = i2c_write(cfg->bus, &select_mask, 1, cfg->slave_addr);
+		if (res == 0) {
+			data->selected_chan = select_mask;
+		}
+	}
+	return res;
+}
+
+static int tca9546a_transfer(const struct device *dev,
+			     struct i2c_msg *msgs,
+			     uint8_t num_msgs,
+			     uint16_t addr)
+{
+	struct tca9546a_root_data *data = get_root_data_from_channel(dev);
+	const struct tca9546a_root_config *config = get_root_config_from_channel(
+		dev);
+	const struct tca9546a_channel_config *down_cfg = dev->config;
+	int res;
+
+	res = k_mutex_lock(&data->lock, K_MSEC(5000));
+	if (res != 0) {
+		return res;
+	}
+
+	res = tca9546a_set_channel(down_cfg->root, down_cfg->chan_mask);
+	if (res != 0) {
+		goto end_trans;
+	}
+
+	res = i2c_transfer(config->bus, msgs, num_msgs, addr);
+
+end_trans:
+	k_mutex_unlock(&data->lock);
+	return res;
+}
+
+static int tca9546_root_init(const struct device *dev)
+{
+	struct tca9546a_root_data *i2c_tca9546a = dev->data;
+	const struct tca9546a_root_config *config = dev->config;
+
+	if (!device_is_ready(config->bus)) {
+		LOG_ERR("I2C bus %s not ready", config->bus->name);
+		return -ENODEV;
+	}
+
+	i2c_tca9546a->selected_chan = 0;
+
+	return 0;
+}
+
+static int tca9546a_channel_init(const struct device *dev)
+{
+	const struct tca9546a_channel_config *cfg = dev->config;
+
+	if (!device_is_ready(cfg->root)) {
+		LOG_ERR("I2C mux root %s not ready", cfg->root->name);
+		return -ENODEV;
+	}
+
+	if (cfg->chan_mask > MAX_CHANNEL_MASK) {
+		LOG_ERR("Wrong DTS address provided for %s", dev->name);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+const struct i2c_driver_api tca9546a_api_funcs = {
+	.configure = tca9546a_configure,
+	.transfer = tca9546a_transfer,
+};
+
+#define TCA9546A_CHILD_DEFINE(node_id)					    \
+	static const struct tca9546a_channel_config			    \
+		tca9546a_down_config_##node_id = {			    \
+		.chan_mask = BIT(DT_REG_ADDR(node_id)),			    \
+		.root = DEVICE_DT_GET(DT_PARENT(node_id)),		    \
+	};								    \
+	DEVICE_DT_DEFINE(node_id,					    \
+			 tca9546a_channel_init,				    \
+			 NULL,						    \
+			 NULL,						    \
+			 &tca9546a_down_config_##node_id,		    \
+			 POST_KERNEL, CONFIG_I2C_TCA9546_CHANNEL_INIT_PRIO, \
+			 &tca9546a_api_funcs);
+
+#define TCA9546A_ROOT_CHILD_DEFINE(inst)				      \
+	static const struct tca9546a_root_config tca9546a_cfg_##inst = {      \
+		.slave_addr = DT_INST_REG_ADDR(inst),			      \
+		.bus = DEVICE_DT_GET(DT_INST_BUS(inst))			      \
+	};								      \
+	static struct tca9546a_root_data tca9546a_data_##inst = {	      \
+		.lock = Z_MUTEX_INITIALIZER(tca9546a_data_0.lock),	      \
+	};								      \
+	DEVICE_DT_INST_DEFINE(inst,					      \
+			      tca9546_root_init, NULL,			      \
+			      &tca9546a_data_##inst, &tca9546a_cfg_##inst,    \
+			      POST_KERNEL, CONFIG_I2C_TCA9546_ROOT_INIT_PRIO, \
+			      NULL);					      \
+	DT_INST_FOREACH_CHILD(inst, TCA9546A_CHILD_DEFINE);
+
+DT_INST_FOREACH_STATUS_OKAY(TCA9546A_ROOT_CHILD_DEFINE)