[PATCH v2 9/9] misc: add FPC202 dual port controller driver

[Romain Gantois <romain.gantois@xxxxxxxxxxx>]

The TI FPC202 dual port controller serves as a low- speed signal aggregator
for common port types such as SFP, QSFP, Mini-SAS HD, and others.

It aggregates GPIO and I2C signals across two downstream ports, acting as
both a GPIO controller and an I2C address translator for up to two logical
devices per port.

Signed-off-by: Romain Gantois <romain.gantois@xxxxxxxxxxx>
---
 MAINTAINERS              |   1 +
 drivers/misc/Kconfig     |  11 ++
 drivers/misc/Makefile    |   1 +
 drivers/misc/ti_fpc202.c | 440 +++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 453 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 8e702cefd2070790330eebf6d2a2b592cadb682d..a9e357b7a1ff95e24b45619eb5521a4fc242251b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -23186,6 +23186,7 @@ M:	Romain Gantois <romain.gantois@xxxxxxxxxxx>
 L:	linux-kernel@xxxxxxxxxxxxxxx
 S:	Maintained
 F:	Documentation/devicetree/bindings/misc/ti,fpc202.yaml
+F:	drivers/misc/ti_fpc202.c
 
 TI FPD-LINK DRIVERS
 M:	Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx>
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 3fe7e2a9bd294da562cf553d958772dcb49bbc89..2549989422c5b1a67a886290efcd692c0835c7e1 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -114,6 +114,17 @@ config RPMB
 
 	  If unsure, select N.
 
+config TI_FPC202
+        tristate "TI FPC202 Dual Port Controller"
+        select GPIOLIB
+        depends on I2C_ATR
+        help
+          If you say yes here you get support for the Texas Instruments FPC202
+          Dual Port Controller.
+
+          This driver can also be built as a module. If so, the module will be
+          called fpc202.
+
 config TIFM_CORE
 	tristate "TI Flash Media interface support"
 	depends on PCI
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index a9f94525e1819d5d7eed4937ce1d50b2875ee71b..d0b7a1b96619b3125d1455d40268040e0764b341 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -12,6 +12,7 @@ obj-$(CONFIG_ATMEL_SSC)		+= atmel-ssc.o
 obj-$(CONFIG_DUMMY_IRQ)		+= dummy-irq.o
 obj-$(CONFIG_ICS932S401)	+= ics932s401.o
 obj-$(CONFIG_LKDTM)		+= lkdtm/
+obj-$(CONFIG_TI_FPC202)         += ti_fpc202.o
 obj-$(CONFIG_TIFM_CORE)       	+= tifm_core.o
 obj-$(CONFIG_TIFM_7XX1)       	+= tifm_7xx1.o
 obj-$(CONFIG_PHANTOM)		+= phantom.o
diff --git a/drivers/misc/ti_fpc202.c b/drivers/misc/ti_fpc202.c
new file mode 100644
index 0000000000000000000000000000000000000000..5ea2ab358098fdabd3c6372b581724bf20265400
--- /dev/null
+++ b/drivers/misc/ti_fpc202.c
@@ -0,0 +1,440 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ti_fpc202.c - FPC202 Dual Port Controller driver
+ *
+ * Copyright (C) 2024 Bootlin
+ *
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/i2c-atr.h>
+#include <linux/gpio/consumer.h>
+#include <linux/gpio/driver.h>
+#include <linux/module.h>
+
+#define FPC202_NUM_PORTS 2
+#define FPC202_ALIASES_PER_PORT 2
+
+/*
+ * GPIO: port mapping
+ *
+ * 0: P0_S0_IN_A
+ * 1: P0_S1_IN_A
+ * 2: P1_S0_IN_A
+ * 3: P1_S1_IN_A
+ * 4: P0_S0_IN_B
+ * ...
+ * 8: P0_S0_IN_C
+ * ...
+ * 12: P0_S0_OUT_A
+ * ...
+ * 16: P0_S0_OUT_B
+ * ...
+ * 19: P1_S1_OUT_B
+ *
+ */
+
+#define FPC202_GPIO_COUNT 20
+#define FPC202_GPIO_P0_S0_IN_B  4
+#define FPC202_GPIO_P0_S0_OUT_A 12
+
+#define FPC202_REG_IN_A_INT    0x6
+#define FPC202_REG_IN_C_IN_B   0x7
+#define FPC202_REG_OUT_A_OUT_B 0x8
+
+#define FPC202_REG_OUT_A_OUT_B_VAL 0xa
+
+#define FPC202_REG_MOD_DEV(port, dev) (0xb4 + ((port) * 4) + (dev))
+#define FPC202_REG_AUX_DEV(port, dev) (0xb6 + ((port) * 4) + (dev))
+
+/*
+ * The FPC202 doesn't support turning off address translation on a single port.
+ * So just set an invalid I2C address as the translation target when no client
+ * address is attached.
+ */
+#define FPC202_REG_DEV_INVALID 0
+
+/* Even aliases are assigned to device 0 and odd aliases to device 1 */
+#define fpc202_dev_num_from_alias(alias) ((alias) % 2)
+
+struct fpc202_priv {
+	struct i2c_client *client;
+	struct i2c_atr *atr;
+	struct gpio_desc *en_gpio;
+	struct gpio_chip gpio;
+
+	/* Lock REG_MOD/AUX_DEV and addr_caches during attach/detach */
+	struct mutex reg_dev_lock;
+
+	/* Cached device addresses for both ports and their devices */
+	u8 addr_caches[2][2];
+};
+
+static void fpc202_fill_alias_table(struct i2c_client *client, u16 *aliases, int port_id)
+{
+	u16 first_alias;
+	int i;
+
+	/*
+	 * There is a predefined list of aliases for each FPC202 I2C
+	 * self-address.  This allows daisy-chained FPC202 units to
+	 * automatically take on different sets of aliases.
+	 * Each port of an FPC202 unit is assigned two aliases from this list.
+	 */
+	first_alias = 0x10 + 4 * port_id + 8 * ((u16)client->addr - 2);
+
+	for (i = 0; i < FPC202_ALIASES_PER_PORT; i++)
+		aliases[i] = first_alias + i;
+}
+
+static int fpc202_gpio_get_dir(int offset)
+{
+	return offset < FPC202_GPIO_P0_S0_OUT_A ? GPIO_LINE_DIRECTION_IN : GPIO_LINE_DIRECTION_OUT;
+}
+
+static int fpc202_read(struct fpc202_priv *priv, u8 reg)
+{
+	int val;
+
+	val = i2c_smbus_read_byte_data(priv->client, reg);
+	return val;
+}
+
+static int fpc202_write(struct fpc202_priv *priv, u8 reg, u8 value)
+{
+	return i2c_smbus_write_byte_data(priv->client, reg, value);
+}
+
+static void fpc202_set_enable(struct fpc202_priv *priv, int enable)
+{
+	if (!priv->en_gpio)
+		return;
+
+	gpiod_set_value(priv->en_gpio, enable);
+}
+
+static void fpc202_gpio_set(struct gpio_chip *chip, unsigned int offset,
+			    int value)
+{
+	struct fpc202_priv *priv = gpiochip_get_data(chip);
+	int ret;
+	u8 val;
+
+	if (fpc202_gpio_get_dir(offset) == GPIO_LINE_DIRECTION_IN)
+		return;
+
+	ret = fpc202_read(priv, FPC202_REG_OUT_A_OUT_B_VAL);
+	if (ret < 0) {
+		dev_err(&priv->client->dev, "Failed to set GPIO %d value! err %d\n", offset, ret);
+		return;
+	}
+
+	val = (u8)ret;
+
+	if (value)
+		val |= BIT(offset - FPC202_GPIO_P0_S0_OUT_A);
+	else
+		val &= ~BIT(offset - FPC202_GPIO_P0_S0_OUT_A);
+
+	fpc202_write(priv, FPC202_REG_OUT_A_OUT_B_VAL, val);
+}
+
+static int fpc202_gpio_get(struct gpio_chip *chip, unsigned int offset)
+{
+	struct fpc202_priv *priv = gpiochip_get_data(chip);
+	u8 reg, bit;
+	int ret;
+
+	if (offset < FPC202_GPIO_P0_S0_IN_B) {
+		reg = FPC202_REG_IN_A_INT;
+		bit = BIT(4 + offset);
+	} else if (offset < FPC202_GPIO_P0_S0_OUT_A) {
+		reg = FPC202_REG_IN_C_IN_B;
+		bit = BIT(offset - FPC202_GPIO_P0_S0_IN_B);
+	} else {
+		reg = FPC202_REG_OUT_A_OUT_B_VAL;
+		bit = BIT(offset - FPC202_GPIO_P0_S0_OUT_A);
+	}
+
+	ret = fpc202_read(priv, reg);
+	if (ret < 0)
+		return ret;
+
+	return !!(((u8)ret) & bit);
+}
+
+static int fpc202_gpio_direction_input(struct gpio_chip *chip, unsigned int offset)
+{
+	if (fpc202_gpio_get_dir(offset) == GPIO_LINE_DIRECTION_OUT)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int fpc202_gpio_direction_output(struct gpio_chip *chip, unsigned int offset,
+					int value)
+{
+	struct fpc202_priv *priv = gpiochip_get_data(chip);
+	int ret;
+	u8 val;
+
+	if (fpc202_gpio_get_dir(offset) == GPIO_LINE_DIRECTION_IN)
+		return -EINVAL;
+
+	fpc202_gpio_set(chip, offset, value);
+
+	ret = fpc202_read(priv, FPC202_REG_OUT_A_OUT_B);
+	if (ret < 0)
+		return ret;
+
+	val = (u8)ret | BIT(offset - FPC202_GPIO_P0_S0_OUT_A);
+
+	return fpc202_write(priv, FPC202_REG_OUT_A_OUT_B, val);
+}
+
+/*
+ * Set the translation table entry associated with a port and device number.
+ *
+ * Each downstream port of the FPC202 has two fixed aliases corresponding to
+ * device numbers 0 and 1. If one of these aliases is found in an incoming I2C
+ * transfer, it will be translated to the address given by the corresponding
+ * translation table entry.
+ */
+static int fpc202_write_dev_addr(struct fpc202_priv *priv, u32 port_id, int dev_num, u16 addr)
+{
+	int ret, reg_mod, reg_aux;
+	u8 val;
+
+	mutex_lock(&priv->reg_dev_lock);
+
+	reg_mod = FPC202_REG_MOD_DEV(port_id, dev_num);
+	reg_aux = FPC202_REG_AUX_DEV(port_id, dev_num);
+	val = addr & 0x7f;
+
+	ret = fpc202_write(priv, reg_mod, val);
+	if (ret)
+		goto out_unlock;
+
+	/*
+	 * The FPC202 datasheet is unclear about the role of the AUX registers.
+	 * Empirically, writing to them as well seems to be necessary for
+	 * address translation to function properly.
+	 */
+	ret = fpc202_write(priv, reg_aux, val);
+
+	priv->addr_caches[port_id][dev_num] = val;
+
+out_unlock:
+	mutex_unlock(&priv->reg_dev_lock);
+	return ret;
+}
+
+static int fpc202_attach_addr(struct i2c_atr *atr, u32 chan_id,
+			      u16 addr, u16 alias)
+{
+	struct fpc202_priv *priv = i2c_atr_get_driver_data(atr);
+
+	dev_dbg(&priv->client->dev, "attaching address 0x%02x to alias 0x%02x\n", addr, alias);
+
+	return fpc202_write_dev_addr(priv, chan_id, fpc202_dev_num_from_alias(alias), addr);
+}
+
+static void fpc202_detach_addr(struct i2c_atr *atr, u32 chan_id,
+			       u16 addr)
+{
+	struct fpc202_priv *priv = i2c_atr_get_driver_data(atr);
+	int dev_num, reg_mod, val;
+
+	for (dev_num = 0; dev_num < 2; dev_num++) {
+		reg_mod = FPC202_REG_MOD_DEV(chan_id, dev_num);
+
+		mutex_lock(&priv->reg_dev_lock);
+
+		val = priv->addr_caches[chan_id][dev_num];
+
+		mutex_unlock(&priv->reg_dev_lock);
+
+		if (val < 0) {
+			dev_err(&priv->client->dev, "failed to read register 0x%x while detaching address 0x%02x\n",
+				reg_mod, addr);
+			return;
+		}
+
+		if (val == (addr & 0x7f)) {
+			fpc202_write_dev_addr(priv, chan_id, dev_num, FPC202_REG_DEV_INVALID);
+			return;
+		}
+	}
+}
+
+static const struct i2c_atr_ops fpc202_atr_ops = {
+	.attach_addr = fpc202_attach_addr,
+	.detach_addr = fpc202_detach_addr,
+};
+
+static int fpc202_probe_port(struct fpc202_priv *priv, int port_id)
+{
+	u16 aliases[FPC202_ALIASES_PER_PORT] = { };
+	struct device *dev = &priv->client->dev;
+	struct i2c_atr_adap_desc desc = { };
+	struct device_node *i2c_handle;
+	u32 addr = -1;
+	int ret = 0;
+
+	if (port_id > 2) {
+		dev_err(dev, "port ID %d is out of range!\n", port_id);
+		return -EINVAL;
+	}
+
+	for_each_child_of_node(dev->of_node, i2c_handle) {
+		ret = of_property_read_u32(i2c_handle, "reg", &addr);
+		if (ret) {
+			dev_err(dev, "failed to read 'reg' property of child node, err %d\n", ret);
+			return ret;
+		}
+
+		if (addr == port_id)
+			break;
+	}
+
+	if (addr != port_id) {
+		dev_err(dev, "failed to find port node %d, err %d\n", port_id, ret);
+		return -EINVAL;
+	}
+
+	desc.chan_id = port_id;
+	desc.parent = dev;
+	desc.bus_handle = of_node_to_fwnode(i2c_handle);
+	desc.num_aliases = FPC202_ALIASES_PER_PORT;
+
+	fpc202_fill_alias_table(priv->client, aliases, port_id);
+	desc.aliases = aliases;
+
+	ret = i2c_atr_add_adapter(priv->atr, &desc);
+	if (ret)
+		return ret;
+
+	of_node_put(i2c_handle);
+
+	ret = fpc202_write_dev_addr(priv, port_id, 0, FPC202_REG_DEV_INVALID);
+	if (ret)
+		return ret;
+
+	return fpc202_write_dev_addr(priv, port_id, 1, FPC202_REG_DEV_INVALID);
+}
+
+static int fpc202_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct fpc202_priv *priv;
+	int ret;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	mutex_init(&priv->reg_dev_lock);
+
+	priv->client = client;
+	i2c_set_clientdata(client, priv);
+
+	priv->en_gpio = devm_gpiod_get_optional(dev, "enable", GPIOD_OUT_HIGH);
+	if (IS_ERR(priv->en_gpio)) {
+		ret = PTR_ERR(priv->en_gpio);
+		dev_err(dev, "failed to fetch enable GPIO! err %d\n", ret);
+		goto destroy_mutex;
+	}
+
+	priv->gpio.label = "gpio-fpc202";
+	priv->gpio.base = -1;
+	priv->gpio.direction_input = fpc202_gpio_direction_input;
+	priv->gpio.direction_output = fpc202_gpio_direction_output;
+	priv->gpio.set = fpc202_gpio_set;
+	priv->gpio.get = fpc202_gpio_get;
+	priv->gpio.ngpio = FPC202_GPIO_COUNT;
+	priv->gpio.parent = dev;
+	priv->gpio.owner = THIS_MODULE;
+
+	ret = gpiochip_add_data(&priv->gpio, priv);
+	if (ret) {
+		priv->gpio.parent = NULL;
+		dev_err(dev, "failed to add gpiochip err %d", ret);
+		goto disable_gpio;
+	}
+
+	priv->atr = i2c_atr_new(client->adapter, dev, &fpc202_atr_ops, 2, I2C_ATR_FLAG_DYNAMIC_C2A);
+	if (IS_ERR(priv->atr)) {
+		ret = PTR_ERR(priv->atr);
+		dev_err(dev, "failed to create i2c atr err %d", ret);
+		goto disable_gpio;
+	}
+
+	i2c_atr_set_driver_data(priv->atr, priv);
+
+	ret = fpc202_probe_port(priv, 0);
+	if (ret) {
+		dev_err(dev, "Failed to probe port 0, err %d\n", ret);
+		goto delete_atr;
+	}
+
+	ret = fpc202_probe_port(priv, 1);
+	if (ret) {
+		dev_err(dev, "Failed to probe port 1, err %d\n", ret);
+		goto unregister_port;
+	}
+
+	dev_info(&client->dev, "%s FPC202 Dual Port controller found\n", client->name);
+
+	goto out;
+
+unregister_port:
+	i2c_atr_del_adapter(priv->atr, 0);
+delete_atr:
+	i2c_atr_delete(priv->atr);
+disable_gpio:
+	fpc202_set_enable(priv, 0);
+	gpiochip_remove(&priv->gpio);
+destroy_mutex:
+	mutex_destroy(&priv->reg_dev_lock);
+out:
+	return ret;
+}
+
+static void fpc202_remove(struct i2c_client *client)
+{
+	struct fpc202_priv *priv = i2c_get_clientdata(client);
+	int port_id;
+
+	for (port_id = 0; port_id < FPC202_NUM_PORTS; port_id++)
+		i2c_atr_del_adapter(priv->atr, port_id);
+
+	mutex_destroy(&priv->reg_dev_lock);
+
+	i2c_atr_delete(priv->atr);
+
+	fpc202_set_enable(priv, 0);
+	gpiochip_remove(&priv->gpio);
+}
+
+static const struct of_device_id fpc202_of_match[] = {
+	{ .compatible = "ti,fpc202" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, fpc202_of_match);
+
+static struct i2c_driver fpc202_driver = {
+	.driver = {
+		.name = "fpc202",
+		.of_match_table = fpc202_of_match,
+	},
+	.probe = fpc202_probe,
+	.remove = fpc202_remove,
+};
+
+module_i2c_driver(fpc202_driver);
+
+MODULE_AUTHOR("Romain Gantois <romain.gantois@xxxxxxxxxxx>");
+MODULE_DESCRIPTION("TI FPC202 Dual Port Controller driver");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS(I2C_ATR);

-- 
2.47.0