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USB: serial: cp210x: fix modem-control handling

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The vendor request used to set the flow-control settings also sets the
state of the modem-control lines.

Add state variables to keep track of the modem-control lines to avoid
always asserting the lines whenever the flow-control settings are
updated.

This specifically also avoids asserting DTR/RTS when opening a port with
the line speed set to B0.

Signed-off-by: Johan Hovold <johan@kernel.org>
This commit is contained in:
Johan Hovold 2021-01-25 14:48:12 +01:00
parent 5951b85088
commit 8cce3bbfb4
1 changed files with 16 additions and 4 deletions
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20
drivers/usb/serial/cp210x.c
View file

@ -269,6 +269,8 @@ struct cp210x_port_private {
struct mutex mutex;
bool crtscts;
bool dtr;
bool rts;
};
static struct usb_serial_driver cp210x_device = {
@ -1162,7 +1164,10 @@ static void cp210x_set_flow_control(struct tty_struct *tty,
ctl_hs &= ~CP210X_SERIAL_DCD_HANDSHAKE;
ctl_hs &= ~CP210X_SERIAL_DSR_SENSITIVITY;
ctl_hs &= ~CP210X_SERIAL_DTR_MASK;
ctl_hs |= CP210X_SERIAL_DTR_SHIFT(CP210X_SERIAL_DTR_ACTIVE);
if (port_priv->dtr)
ctl_hs |= CP210X_SERIAL_DTR_SHIFT(CP210X_SERIAL_DTR_ACTIVE);
else
ctl_hs |= CP210X_SERIAL_DTR_SHIFT(CP210X_SERIAL_DTR_INACTIVE);
if (C_CRTSCTS(tty)) {
ctl_hs |= CP210X_SERIAL_CTS_HANDSHAKE;
@ -1172,7 +1177,10 @@ static void cp210x_set_flow_control(struct tty_struct *tty,
} else {
ctl_hs &= ~CP210X_SERIAL_CTS_HANDSHAKE;
flow_repl &= ~CP210X_SERIAL_RTS_MASK;
flow_repl |= CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_ACTIVE);
if (port_priv->rts)
flow_repl |= CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_ACTIVE);
else
flow_repl |= CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_INACTIVE);
port_priv->crtscts = false;
}
@ -1287,25 +1295,29 @@ static int cp210x_tiocmset_port(struct usb_serial_port *port,
u16 control = 0;
int ret;
mutex_lock(&port_priv->mutex);
if (set & TIOCM_RTS) {
port_priv->rts = true;
control |= CONTROL_RTS;
control |= CONTROL_WRITE_RTS;
}
if (set & TIOCM_DTR) {
port_priv->dtr = true;
control |= CONTROL_DTR;
control |= CONTROL_WRITE_DTR;
}
if (clear & TIOCM_RTS) {
port_priv->rts = false;
control &= ~CONTROL_RTS;
control |= CONTROL_WRITE_RTS;
}
if (clear & TIOCM_DTR) {
port_priv->dtr = false;
control &= ~CONTROL_DTR;
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.