USB: serial: ftdi_sio: implement GPIO support for FT-X devices

This patch allows using the CBUS pins of FT-X devices as GPIO in CBUS
bitbanging mode. There is no conflict between the GPIO and VCP
functionality in this mode. Tested on FT230X and FT231X.

As there is no way to request the current CBUS register configuration
from the device, all CBUS pins are set to a known state when the first
GPIO is requested. This allows using libftdi to set the GPIO pins
before loading this module for UART functionality, a behavior that
existing applications might be relying upon (though no specific case
is known to the authors of this patch).

Signed-off-by: Karoly Pados <pados@pados.hu>
[ johan: minor style changes ]
Signed-off-by: Johan Hovold <johan@kernel.org>

1 files changed, 359 insertions, 1 deletions

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index b5cef322826f..6b727ada20cf 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -39,6 +39,7 @@
 #include <linux/uaccess.h>
 #include <linux/usb.h>
 #include <linux/serial.h>
+#include <linux/gpio/driver.h>
 #include <linux/usb/serial.h>
 #include "ftdi_sio.h"
 #include "ftdi_sio_ids.h"
@@ -72,6 +73,15 @@ struct ftdi_private {
 	unsigned int latency;		/* latency setting in use */
 	unsigned short max_packet_size;
 	struct mutex cfg_lock; /* Avoid mess by parallel calls of config ioctl() and change_speed() */
+#ifdef CONFIG_GPIOLIB
+	struct gpio_chip gc;
+	struct mutex gpio_lock;	/* protects GPIO state */
+	bool gpio_registered;	/* is the gpiochip in kernel registered */
+	bool gpio_used;		/* true if the user requested a gpio */
+	u8 gpio_altfunc;	/* which pins are in gpio mode */
+	u8 gpio_output;		/* pin directions cache */
+	u8 gpio_value;		/* pin value for outputs */
+#endif
 };
 
 /* struct ftdi_sio_quirk is used by devices requiring special attention. */
@@ -1766,6 +1776,344 @@ static void remove_sysfs_attrs(struct usb_serial_port *port)
 
 }
 
+#ifdef CONFIG_GPIOLIB
+
+static const char * const ftdi_ftx_gpio_names[] = {
+	"CBUS0", "CBUS1", "CBUS2", "CBUS3"
+};
+
+static int ftdi_set_bitmode(struct usb_serial_port *port, u8 mode)
+{
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+	struct usb_serial *serial = port->serial;
+	int result;
+	u16 val;
+
+	val = (mode << 8) | (priv->gpio_output << 4) | priv->gpio_value;
+	result = usb_control_msg(serial->dev,
+				 usb_sndctrlpipe(serial->dev, 0),
+				 FTDI_SIO_SET_BITMODE_REQUEST,
+				 FTDI_SIO_SET_BITMODE_REQUEST_TYPE, val,
+				 priv->interface, NULL, 0, WDR_TIMEOUT);
+	if (result < 0) {
+		dev_err(&serial->interface->dev,
+			"bitmode request failed for value 0x%04x: %d\n",
+			val, result);
+	}
+
+	return result;
+}
+
+static int ftdi_set_cbus_pins(struct usb_serial_port *port)
+{
+	return ftdi_set_bitmode(port, FTDI_SIO_BITMODE_CBUS);
+}
+
+static int ftdi_exit_cbus_mode(struct usb_serial_port *port)
+{
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+
+	priv->gpio_output = 0;
+	priv->gpio_value = 0;
+	return ftdi_set_bitmode(port, FTDI_SIO_BITMODE_RESET);
+}
+
+static int ftdi_gpio_request(struct gpio_chip *gc, unsigned int offset)
+{
+	struct usb_serial_port *port = gpiochip_get_data(gc);
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+	int result;
+
+	if (priv->gpio_altfunc & BIT(offset))
+		return -ENODEV;
+
+	mutex_lock(&priv->gpio_lock);
+	if (!priv->gpio_used) {
+		/* Set default pin states, as we cannot get them from device */
+		priv->gpio_output = 0x00;
+		priv->gpio_value = 0x00;
+		result = ftdi_set_cbus_pins(port);
+		if (result) {
+			mutex_unlock(&priv->gpio_lock);
+			return result;
+		}
+
+		priv->gpio_used = true;
+	}
+	mutex_unlock(&priv->gpio_lock);
+
+	return 0;
+}
+
+static int ftdi_read_cbus_pins(struct usb_serial_port *port)
+{
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+	struct usb_serial *serial = port->serial;
+	unsigned char *buf;
+	int result;
+
+	buf = kmalloc(1, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	result = usb_control_msg(serial->dev,
+				 usb_rcvctrlpipe(serial->dev, 0),
+				 FTDI_SIO_READ_PINS_REQUEST,
+				 FTDI_SIO_READ_PINS_REQUEST_TYPE, 0,
+				 priv->interface, buf, 1, WDR_TIMEOUT);
+	if (result < 1) {
+		if (result >= 0)
+			result = -EIO;
+	} else {
+		result = buf[0];
+	}
+
+	kfree(buf);
+
+	return result;
+}
+
+static int ftdi_gpio_get(struct gpio_chip *gc, unsigned int gpio)
+{
+	struct usb_serial_port *port = gpiochip_get_data(gc);
+	int result;
+
+	result = ftdi_read_cbus_pins(port);
+	if (result < 0)
+		return result;
+
+	return !!(result & BIT(gpio));
+}
+
+static void ftdi_gpio_set(struct gpio_chip *gc, unsigned int gpio, int value)
+{
+	struct usb_serial_port *port = gpiochip_get_data(gc);
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+
+	mutex_lock(&priv->gpio_lock);
+
+	if (value)
+		priv->gpio_value |= BIT(gpio);
+	else
+		priv->gpio_value &= ~BIT(gpio);
+
+	ftdi_set_cbus_pins(port);
+
+	mutex_unlock(&priv->gpio_lock);
+}
+
+static int ftdi_gpio_get_multiple(struct gpio_chip *gc, unsigned long *mask,
+					unsigned long *bits)
+{
+	struct usb_serial_port *port = gpiochip_get_data(gc);
+	int result;
+
+	result = ftdi_read_cbus_pins(port);
+	if (result < 0)
+		return result;
+
+	*bits = result & *mask;
+
+	return 0;
+}
+
+static void ftdi_gpio_set_multiple(struct gpio_chip *gc, unsigned long *mask,
+					unsigned long *bits)
+{
+	struct usb_serial_port *port = gpiochip_get_data(gc);
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+
+	mutex_lock(&priv->gpio_lock);
+
+	priv->gpio_value &= ~(*mask);
+	priv->gpio_value |= *bits & *mask;
+	ftdi_set_cbus_pins(port);
+
+	mutex_unlock(&priv->gpio_lock);
+}
+
+static int ftdi_gpio_direction_get(struct gpio_chip *gc, unsigned int gpio)
+{
+	struct usb_serial_port *port = gpiochip_get_data(gc);
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+
+	return !(priv->gpio_output & BIT(gpio));
+}
+
+static int ftdi_gpio_direction_input(struct gpio_chip *gc, unsigned int gpio)
+{
+	struct usb_serial_port *port = gpiochip_get_data(gc);
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+	int result;
+
+	mutex_lock(&priv->gpio_lock);
+
+	priv->gpio_output &= ~BIT(gpio);
+	result = ftdi_set_cbus_pins(port);
+
+	mutex_unlock(&priv->gpio_lock);
+
+	return result;
+}
+
+static int ftdi_gpio_direction_output(struct gpio_chip *gc, unsigned int gpio,
+					int value)
+{
+	struct usb_serial_port *port = gpiochip_get_data(gc);
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+	int result;
+
+	mutex_lock(&priv->gpio_lock);
+
+	priv->gpio_output |= BIT(gpio);
+	if (value)
+		priv->gpio_value |= BIT(gpio);
+	else
+		priv->gpio_value &= ~BIT(gpio);
+
+	result = ftdi_set_cbus_pins(port);
+
+	mutex_unlock(&priv->gpio_lock);
+
+	return result;
+}
+
+static int ftdi_read_eeprom(struct usb_serial *serial, void *dst, u16 addr,
+				u16 nbytes)
+{
+	int read = 0;
+
+	if (addr % 2 != 0)
+		return -EINVAL;
+	if (nbytes % 2 != 0)
+		return -EINVAL;
+
+	/* Read EEPROM two bytes at a time */
+	while (read < nbytes) {
+		int rv;
+
+		rv = usb_control_msg(serial->dev,
+				     usb_rcvctrlpipe(serial->dev, 0),
+				     FTDI_SIO_READ_EEPROM_REQUEST,
+				     FTDI_SIO_READ_EEPROM_REQUEST_TYPE,
+				     0, (addr + read) / 2, dst + read, 2,
+				     WDR_TIMEOUT);
+		if (rv < 2) {
+			if (rv >= 0)
+				return -EIO;
+			else
+				return rv;
+		}
+
+		read += rv;
+	}
+
+	return 0;
+}
+
+static int ftx_gpioconf_init(struct usb_serial_port *port)
+{
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+	struct usb_serial *serial = port->serial;
+	const u16 cbus_cfg_addr = 0x1a;
+	const u16 cbus_cfg_size = 4;
+	u8 *cbus_cfg_buf;
+	int result;
+	u8 i;
+
+	cbus_cfg_buf = kmalloc(cbus_cfg_size, GFP_KERNEL);
+	if (!cbus_cfg_buf)
+		return -ENOMEM;
+
+	result = ftdi_read_eeprom(serial, cbus_cfg_buf,
+				  cbus_cfg_addr, cbus_cfg_size);
+	if (result < 0)
+		goto out_free;
+
+	/* FIXME: FT234XD alone has 1 GPIO, but how to recognize this IC? */
+	priv->gc.ngpio = 4;
+	priv->gc.names = ftdi_ftx_gpio_names;
+
+	/* Determine which pins are configured for CBUS bitbanging */
+	priv->gpio_altfunc = 0xff;
+	for (i = 0; i < priv->gc.ngpio; ++i) {
+		if (cbus_cfg_buf[i] == FTDI_FTX_CBUS_MUX_GPIO)
+			priv->gpio_altfunc &= ~BIT(i);
+	}
+
+out_free:
+	kfree(cbus_cfg_buf);
+
+	return result;
+}
+
+static int ftdi_gpio_init(struct usb_serial_port *port)
+{
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+	struct usb_serial *serial = port->serial;
+	int result;
+
+	switch (priv->chip_type) {
+	case FTX:
+		result = ftx_gpioconf_init(port);
+		break;
+	default:
+		return 0;
+	}
+
+	if (result < 0)
+		return result;
+
+	mutex_init(&priv->gpio_lock);
+
+	priv->gc.label = "ftdi-cbus";
+	priv->gc.request = ftdi_gpio_request;
+	priv->gc.get_direction = ftdi_gpio_direction_get;
+	priv->gc.direction_input = ftdi_gpio_direction_input;
+	priv->gc.direction_output = ftdi_gpio_direction_output;
+	priv->gc.get = ftdi_gpio_get;
+	priv->gc.set = ftdi_gpio_set;
+	priv->gc.get_multiple = ftdi_gpio_get_multiple;
+	priv->gc.set_multiple = ftdi_gpio_set_multiple;
+	priv->gc.owner = THIS_MODULE;
+	priv->gc.parent = &serial->interface->dev;
+	priv->gc.base = -1;
+	priv->gc.can_sleep = true;
+
+	result = gpiochip_add_data(&priv->gc, port);
+	if (!result)
+		priv->gpio_registered = true;
+
+	return result;
+}
+
+static void ftdi_gpio_remove(struct usb_serial_port *port)
+{
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+
+	if (priv->gpio_registered) {
+		gpiochip_remove(&priv->gc);
+		priv->gpio_registered = false;
+	}
+
+	if (priv->gpio_used) {
+		/* Exiting CBUS-mode does not reset pin states. */
+		ftdi_exit_cbus_mode(port);
+		priv->gpio_used = false;
+	}
+}
+
+#else
+
+static int ftdi_gpio_init(struct usb_serial_port *port)
+{
+	return 0;
+}
+
+static void ftdi_gpio_remove(struct usb_serial_port *port) { }
+
+#endif	/* CONFIG_GPIOLIB */
+
 /*
  * ***************************************************************************
  * FTDI driver specific functions
@@ -1794,7 +2142,7 @@ static int ftdi_sio_port_probe(struct usb_serial_port *port)
 {
 	struct ftdi_private *priv;
 	const struct ftdi_sio_quirk *quirk = usb_get_serial_data(port->serial);
-
+	int result;
 
 	priv = kzalloc(sizeof(struct ftdi_private), GFP_KERNEL);
 	if (!priv)
@@ -1813,6 +2161,14 @@ static int ftdi_sio_port_probe(struct usb_serial_port *port)
 		priv->latency = 16;
 	write_latency_timer(port);
 	create_sysfs_attrs(port);
+
+	result = ftdi_gpio_init(port);
+	if (result < 0) {
+		dev_err(&port->serial->interface->dev,
+			"GPIO initialisation failed: %d\n",
+			result);
+	}
+
 	return 0;
 }
 
@@ -1930,6 +2286,8 @@ static int ftdi_sio_port_remove(struct usb_serial_port *port)
 {
 	struct ftdi_private *priv = usb_get_serial_port_data(port);
 
+	ftdi_gpio_remove(port);
+
 	remove_sysfs_attrs(port);
 
 	kfree(priv);