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USB: serial: xr: add TIOCGRS485 and TIOCSRS485 ioctls

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Exar devices like XR21B1411 can control an RS485 transceiver by
automatically asserting the RTS#/RS485 pin before sending data
and deasserting it when the last stop bit has been transmitted.
The polarity of the RST#/RS485 signal is configurable and the
hardware also supports half-duplex turn-around delay and
address matching mode.

Add support for enabling and disabling RS-485 mode and
configuring the RST#/RS485 signal polarity using the TIOCGRS485
and TIOCSRS485 ioctls. Support for half-duplex turn-around delay
and address matching mode are left unimplemented for now.

User enables RS-485 mode by setting SER_RS485_ENABLED flag in
struct serial_rs485 flags. User should also set either
SER_RS485_RTS_ON_SEND or SER_RS485_RTS_AFTER_SEND to select the
behaviour of the RTS#/RS485 pin. Setting SER_RS485_RTS_ON_SEND
will drive RTS#/RS485 low during transmission.

Signed-off-by: Jarkko Sonninen <kasper@iki.fi>
[ johan: let SER_RS485_RTS_ON_SEND determine SER_RS485_RTS_AFTER_SEND ]
Signed-off-by: Johan Hovold <johan@kernel.org>
This commit is contained in:
Jarkko Sonninen 2023-07-08 17:56:50 +03:00 committed by Johan Hovold
parent fdf0eaf114
commit 974e2f6a05
1 changed files with 88 additions and 1 deletions
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89
drivers/usb/serial/xr_serial.c
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@ -93,6 +93,7 @@ struct xr_txrx_clk_mask {
#define XR_GPIO_MODE_SEL_DTR_DSR 0x2
#define XR_GPIO_MODE_SEL_RS485 0x3
#define XR_GPIO_MODE_SEL_RS485_ADDR 0x4
#define XR_GPIO_MODE_RS485_TX_H 0x8
#define XR_GPIO_MODE_TX_TOGGLE 0x100
#define XR_GPIO_MODE_RX_TOGGLE 0x200
@ -237,6 +238,7 @@ static const struct xr_type xr_types[] = {
struct xr_data {
const struct xr_type *type;
u8 channel; /* zero-based index or interface number */
struct serial_rs485 rs485;
};
static int xr_set_reg(struct usb_serial_port *port, u8 channel, u16 reg, u16 val)
@ -629,6 +631,7 @@ static void xr_set_flow_mode(struct tty_struct *tty,
struct xr_data *data = usb_get_serial_port_data(port);
const struct xr_type *type = data->type;
u16 flow, gpio_mode;
bool rs485_enabled;
int ret;
ret = xr_get_reg_uart(port, type->gpio_mode, &gpio_mode);
@ -645,7 +648,17 @@ static void xr_set_flow_mode(struct tty_struct *tty,
/* Set GPIO mode for controlling the pins manually by default. */
gpio_mode &= ~XR_GPIO_MODE_SEL_MASK;
if (C_CRTSCTS(tty) && C_BAUD(tty) != B0) {
rs485_enabled = !!(data->rs485.flags & SER_RS485_ENABLED);
if (rs485_enabled) {
dev_dbg(&port->dev, "Enabling RS-485\n");
gpio_mode |= XR_GPIO_MODE_SEL_RS485;
if (data->rs485.flags & SER_RS485_RTS_ON_SEND)
gpio_mode &= ~XR_GPIO_MODE_RS485_TX_H;
else
gpio_mode |= XR_GPIO_MODE_RS485_TX_H;
}
if (C_CRTSCTS(tty) && C_BAUD(tty) != B0 && !rs485_enabled) {
dev_dbg(&port->dev, "Enabling hardware flow ctrl\n");
gpio_mode |= XR_GPIO_MODE_SEL_RTS_CTS;
flow = XR_UART_FLOW_MODE_HW;
@ -809,6 +822,79 @@ static void xr_cdc_set_line_coding(struct tty_struct *tty,
kfree(lc);
}
static void xr_sanitize_serial_rs485(struct serial_rs485 *rs485)
{
if (!(rs485->flags & SER_RS485_ENABLED)) {
memset(rs485, 0, sizeof(*rs485));
return;
}
/* RTS always toggles after TX */
if (rs485->flags & SER_RS485_RTS_ON_SEND)
rs485->flags &= ~SER_RS485_RTS_AFTER_SEND;
else
rs485->flags |= SER_RS485_RTS_AFTER_SEND;
/* Only the flags are implemented at the moment */
rs485->flags &= SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND |
SER_RS485_RTS_AFTER_SEND;
rs485->delay_rts_before_send = 0;
rs485->delay_rts_after_send = 0;
memset(rs485->padding, 0, sizeof(rs485->padding));
}
static int xr_get_rs485_config(struct tty_struct *tty,
struct serial_rs485 __user *argp)
{
struct usb_serial_port *port = tty->driver_data;
struct xr_data *data = usb_get_serial_port_data(port);
down_read(&tty->termios_rwsem);
if (copy_to_user(argp, &data->rs485, sizeof(data->rs485))) {
up_read(&tty->termios_rwsem);
return -EFAULT;
}
up_read(&tty->termios_rwsem);
return 0;
}
static int xr_set_rs485_config(struct tty_struct *tty,
struct serial_rs485 __user *argp)
{
struct usb_serial_port *port = tty->driver_data;
struct xr_data *data = usb_get_serial_port_data(port);
struct serial_rs485 rs485;
if (copy_from_user(&rs485, argp, sizeof(rs485)))
return -EFAULT;
xr_sanitize_serial_rs485(&rs485);
down_write(&tty->termios_rwsem);
data->rs485 = rs485;
xr_set_flow_mode(tty, port, NULL);
up_write(&tty->termios_rwsem);
if (copy_to_user(argp, &rs485, sizeof(rs485)))
return -EFAULT;
return 0;
}
static int xr_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
{
void __user *argp = (void __user *)arg;
switch (cmd) {
case TIOCGRS485:
return xr_get_rs485_config(tty, argp);
case TIOCSRS485:
return xr_set_rs485_config(tty, argp);
}
return -ENOIOCTLCMD;
}
static void xr_set_termios(struct tty_struct *tty,
struct usb_serial_port *port,
const struct ktermios *old_termios)
@ -1010,6 +1096,7 @@ static struct usb_serial_driver xr_device = {
.set_termios = xr_set_termios,
.tiocmget = xr_tiocmget,
.tiocmset = xr_tiocmset,
.ioctl = xr_ioctl,
.dtr_rts = xr_dtr_rts
};