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@xxxxxxxxxx>
---
drivers/usb/serial/cp210x.c | 47 +++++++++++++++++++++++++++++++------
1 file changed, 40 insertions(+), 7 deletions(-)
diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index 4ba3fb096bf1..f00b736f3cd3 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -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;
--
2.26.2
