From 5951b8508855799fbb2d6a9553ab3b7af595ea94 Mon Sep 17 00:00:00 2001 From: Johan Hovold Date: Mon, 25 Jan 2021 14:48:11 +0100 Subject: [PATCH] USB: serial: cp210x: suppress modem-control errors The CP210X_SET_MHS request cannot be used to control RTS when hardware flow control (auto-RTS) is enabled and instead returns an error which is currently logged as: cp210x ttyUSB0: failed set request 0x7 status: -32 when opening and closing a port (and on TIOCMSET requests). Add a crtscts flag to keep track of the hardware flow-control setting and use it to suppress any request to change RTS when auto-RTS is enabled. Note that RTS is still deasserted when disabling the UART as part of close. Reported-by: Pho Tran Signed-off-by: Johan Hovold --- drivers/usb/serial/cp210x.c | 33 ++++++++++++++++++++++++++++++--- 1 file changed, 30 insertions(+), 3 deletions(-) diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c index d813a052738f..7e4a09b42c99 100644 --- a/drivers/usb/serial/cp210x.c +++ b/drivers/usb/serial/cp210x.c @@ -21,6 +21,7 @@ #include #include #include +#include #define DRIVER_DESC "Silicon Labs CP210x RS232 serial adaptor driver" @@ -264,7 +265,10 @@ struct cp210x_port_private { u8 bInterfaceNumber; bool event_mode; enum cp210x_event_state event_state; - u8 lsr; + u8 lsr; + + struct mutex mutex; + bool crtscts; }; static struct usb_serial_driver cp210x_device = { @@ -1117,6 +1121,7 @@ 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_port_private *port_priv = usb_get_serial_port_data(port); struct cp210x_special_chars chars; struct cp210x_flow_ctl flow_ctl; u32 flow_repl; @@ -1143,10 +1148,12 @@ static void cp210x_set_flow_control(struct tty_struct *tty, return; } + mutex_lock(&port_priv->mutex); + ret = cp210x_read_reg_block(port, CP210X_GET_FLOW, &flow_ctl, sizeof(flow_ctl)); if (ret) - return; + goto out_unlock; ctl_hs = le32_to_cpu(flow_ctl.ulControlHandshake); flow_repl = le32_to_cpu(flow_ctl.ulFlowReplace); @@ -1161,10 +1168,12 @@ static void cp210x_set_flow_control(struct tty_struct *tty, ctl_hs |= CP210X_SERIAL_CTS_HANDSHAKE; flow_repl &= ~CP210X_SERIAL_RTS_MASK; flow_repl |= CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_FLOW_CTL); + port_priv->crtscts = true; } else { ctl_hs &= ~CP210X_SERIAL_CTS_HANDSHAKE; flow_repl &= ~CP210X_SERIAL_RTS_MASK; flow_repl |= CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_ACTIVE); + port_priv->crtscts = false; } if (I_IXOFF(tty)) @@ -1188,6 +1197,8 @@ static void cp210x_set_flow_control(struct tty_struct *tty, cp210x_write_reg_block(port, CP210X_SET_FLOW, &flow_ctl, sizeof(flow_ctl)); +out_unlock: + mutex_unlock(&port_priv->mutex); } static void cp210x_set_termios(struct tty_struct *tty, @@ -1272,7 +1283,9 @@ static int cp210x_tiocmset(struct tty_struct *tty, static int cp210x_tiocmset_port(struct usb_serial_port *port, unsigned int set, unsigned int clear) { + struct cp210x_port_private *port_priv = usb_get_serial_port_data(port); u16 control = 0; + int ret; if (set & TIOCM_RTS) { control |= CONTROL_RTS; @@ -1291,9 +1304,22 @@ static int cp210x_tiocmset_port(struct usb_serial_port *port, control |= CONTROL_WRITE_DTR; } + mutex_lock(&port_priv->mutex); + + /* + * SET_MHS cannot be used to control RTS when auto-RTS is enabled. + * Note that RTS is still deasserted when disabling the UART on close. + */ + if (port_priv->crtscts) + control &= ~CONTROL_WRITE_RTS; + dev_dbg(&port->dev, "%s - control = 0x%.4x\n", __func__, control); - return cp210x_write_u16_reg(port, CP210X_SET_MHS, control); + ret = cp210x_write_u16_reg(port, CP210X_SET_MHS, control); + + mutex_unlock(&port_priv->mutex); + + return ret; } static void cp210x_dtr_rts(struct usb_serial_port *port, int on) @@ -1770,6 +1796,7 @@ static int cp210x_port_probe(struct usb_serial_port *port) return -ENOMEM; port_priv->bInterfaceNumber = cp210x_interface_num(serial); + mutex_init(&port_priv->mutex); usb_set_serial_port_data(port, port_priv);