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USB: serial: cp210x: fix RTS handling 

Clearing TIOCM_RTS should always deassert RTS and setting the same bit
should enable auto-RTS if hardware flow control is enabled.

This allows user space to throttle input directly at the source also
when hardware-assisted flow control is enabled and makes dtr_rts()
always deassert both lines during close (when HUPCL is set).

Signed-off-by: Johan Hovold <johan@kernel.org>
This commit is contained in:
Johan Hovold 2021-01-25 14:48:16 +01:00
parent 6b667274f4
commit cf00ead0bd
1 changed files with 40 additions and 7 deletions
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47
drivers/usb/serial/cp210x.c
View File

@ -1166,7 +1166,10 @@ static void cp210x_set_flow_control(struct tty_struct *tty,
if (C_CRTSCTS(tty)) {
ctl_hs |= CP210X_SERIAL_CTS_HANDSHAKE;
flow_repl &= ~CP210X_SERIAL_RTS_MASK;
flow_repl |= CP210X_SERIAL_RTS_FLOW_CTL;
if (port_priv->rts)
flow_repl |= CP210X_SERIAL_RTS_FLOW_CTL;
else
flow_repl |= CP210X_SERIAL_RTS_INACTIVE;
port_priv->crtscts = true;
} else {
ctl_hs &= ~CP210X_SERIAL_CTS_HANDSHAKE;
@ -1286,6 +1289,8 @@ 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);
struct cp210x_flow_ctl flow_ctl;
u32 ctl_hs, flow_repl;
u16 control = 0;
int ret;
@ -1313,16 +1318,44 @@ static int cp210x_tiocmset_port(struct usb_serial_port *port,
}
/*
* 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.
* Use SET_FLOW to set DTR and enable/disable auto-RTS when hardware
* flow control is enabled.
*/
if (port_priv->crtscts)
control &= ~CONTROL_WRITE_RTS;
if (port_priv->crtscts && control & CONTROL_WRITE_RTS) {
ret = cp210x_read_reg_block(port, CP210X_GET_FLOW, &flow_ctl,
sizeof(flow_ctl));
if (ret)
goto out_unlock;
dev_dbg(&port->dev, "%s - control = 0x%04x\n", __func__, control);
ctl_hs = le32_to_cpu(flow_ctl.ulControlHandshake);
flow_repl = le32_to_cpu(flow_ctl.ulFlowReplace);
ret = cp210x_write_u16_reg(port, CP210X_SET_MHS, control);
ctl_hs &= ~CP210X_SERIAL_DTR_MASK;
if (port_priv->dtr)
ctl_hs |= CP210X_SERIAL_DTR_ACTIVE;
else
ctl_hs |= CP210X_SERIAL_DTR_INACTIVE;
flow_repl &= ~CP210X_SERIAL_RTS_MASK;
if (port_priv->rts)
flow_repl |= CP210X_SERIAL_RTS_FLOW_CTL;
else
flow_repl |= CP210X_SERIAL_RTS_INACTIVE;
flow_ctl.ulControlHandshake = cpu_to_le32(ctl_hs);
flow_ctl.ulFlowReplace = cpu_to_le32(flow_repl);
dev_dbg(&port->dev, "%s - ctrl = 0x%02x, flow = 0x%02x\n",
__func__, ctl_hs, flow_repl);
ret = cp210x_write_reg_block(port, CP210X_SET_FLOW, &flow_ctl,
sizeof(flow_ctl));
} else {
dev_dbg(&port->dev, "%s - control = 0x%04x\n", __func__, control);
ret = cp210x_write_u16_reg(port, CP210X_SET_MHS, control);
}
out_unlock:
mutex_unlock(&port_priv->mutex);
return ret;