From: Wang Sheng Long <shenglong.wang.ext@xxxxxxxxxxx> When data is transmitted between two serial ports, the phenomenon of data loss often occurs. The two kinds of flow control commonly used in serial communication are hardware flow control and software flow control. In serial communication, If you only use RX/TX/GND Pins, you can't do hardware flow. So we often used software flow control and prevent data loss. The user sets the software flow control through the application program, and the application program sets the software flow control mode for the serial port chip through the driver. For the cp210 serial port chip, its driver lacks the software flow control setting code, so the user cannot set the software flow control function through the application program. This adds the missing software flow control. Signed-off-by: Wang Sheng Long <shenglong.wang.ext@xxxxxxxxxxx> Link: https://lore.kernel.org/r/20210104094502.3942-1-china_shenglong@xxxxxxx [ johan: rework properly on top of recent termios changes ] Signed-off-by: Johan Hovold <johan@xxxxxxxxxx> --- drivers/usb/serial/cp210x.c | 67 +++++++++++++++++++++++++++++++++++-- 1 file changed, 65 insertions(+), 2 deletions(-) diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c index fbb10dfc56e3..5bd14770065b 100644 --- a/drivers/usb/serial/cp210x.c +++ b/drivers/usb/serial/cp210x.c @@ -377,6 +377,16 @@ static struct usb_serial_driver * const serial_drivers[] = { #define CONTROL_WRITE_DTR 0x0100 #define CONTROL_WRITE_RTS 0x0200 +/* CP210X_(GET|SET)_CHARS */ +struct cp210x_special_chars { + u8 bEofChar; + u8 bErrorChar; + u8 bBreakChar; + u8 bEventChar; + u8 bXonChar; + u8 bXoffChar; +}; + /* CP210X_VENDOR_SPECIFIC values */ #define CP210X_READ_2NCONFIG 0x000E #define CP210X_READ_LATCH 0x00C2 @@ -1074,11 +1084,38 @@ static void cp210x_disable_event_mode(struct usb_serial_port *port) port_priv->event_mode = false; } +static int cp210x_set_chars(struct usb_serial_port *port, + struct cp210x_special_chars *chars) +{ + struct cp210x_port_private *port_priv = usb_get_serial_port_data(port); + struct usb_serial *serial = port->serial; + void *dmabuf; + int result; + + dmabuf = kmemdup(chars, sizeof(*chars), GFP_KERNEL); + if (!dmabuf) + return -ENOMEM; + + result = usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0), + CP210X_SET_CHARS, REQTYPE_HOST_TO_INTERFACE, 0, + port_priv->bInterfaceNumber, + dmabuf, sizeof(*chars), USB_CTRL_SET_TIMEOUT); + + kfree(dmabuf); + + if (result < 0) { + dev_err(&port->dev, "failed to set special chars: %d\n", result); + return result; + } + + return 0; +} + static bool cp210x_termios_change(const struct ktermios *a, const struct ktermios *b) { bool iflag_change; - iflag_change = ((a->c_iflag ^ b->c_iflag) & INPCK); + iflag_change = ((a->c_iflag ^ b->c_iflag) & (INPCK | IXON | IXOFF)); return tty_termios_hw_change(a, b) || iflag_change; } @@ -1086,13 +1123,29 @@ static bool cp210x_termios_change(const struct ktermios *a, const struct ktermio static void cp210x_set_flow_control(struct tty_struct *tty, struct usb_serial_port *port, struct ktermios *old_termios) { + struct cp210x_special_chars chars; struct cp210x_flow_ctl flow_ctl; u32 flow_repl; u32 ctl_hs; int ret; - if (old_termios && C_CRTSCTS(tty) == (old_termios->c_cflag & CRTSCTS)) + if (old_termios && + C_CRTSCTS(tty) == (old_termios->c_cflag & CRTSCTS) && + I_IXON(tty) == (old_termios->c_iflag & IXON) && + I_IXOFF(tty) == (old_termios->c_iflag & IXOFF)) { return; + } + + if (I_IXON(tty) || I_IXOFF(tty)) { + memset(&chars, 0, sizeof(chars)); + + chars.bXonChar = START_CHAR(tty); + chars.bXoffChar = STOP_CHAR(tty); + + ret = cp210x_set_chars(port, &chars); + if (ret) + return; + } ret = cp210x_read_reg_block(port, CP210X_GET_FLOW, &flow_ctl, sizeof(flow_ctl)); @@ -1118,6 +1171,16 @@ static void cp210x_set_flow_control(struct tty_struct *tty, flow_repl |= CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_ACTIVE); } + if (I_IXOFF(tty)) + flow_repl |= CP210X_SERIAL_AUTO_RECEIVE; + else + flow_repl &= ~CP210X_SERIAL_AUTO_RECEIVE; + + if (I_IXON(tty)) + flow_repl |= CP210X_SERIAL_AUTO_TRANSMIT; + else + flow_repl &= ~CP210X_SERIAL_AUTO_TRANSMIT; + dev_dbg(&port->dev, "%s - ulControlHandshake=0x%08x, ulFlowReplace=0x%08x\n", __func__, ctl_hs, flow_repl); -- 2.26.2
