Fix error 32 returned by CP210X_SET_MHS when hardware flow control is enabled.
The root cause of error 32 is that user application (CoolTerm, linux-serial-test)
opened cp210x device with hardware flow control then attempt to control RTS/DTR pins.
In hardware flow control, RTS/DTR pins will be controlled by hardware only,
any attempt to control those pins will cause error 32 from the device.
This fix will block MHS command(command to control RTS/DTR pins) to the device
if hardware flow control is being used.
Signed-off-by: Pho Tran <pho.tran@xxxxxxxxxx>
---
drivers/usb/serial/cp210x.c | 27 +++++++++++++++++++++++++++
1 file changed, 27 insertions(+)
diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index fbb10dfc56e3..3694b7c62290 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -1211,6 +1211,12 @@ static int cp210x_tiocmset_port(struct usb_serial_port *port,
unsigned int set, unsigned int clear)
{
u16 control = 0;
+ struct cp210x_flow_ctl flow_ctl;
+ u32 ctl_hs = 0;
+ u32 flow_repl = 0;
+ bool auto_dtr = false;
+ bool auto_rts = false;
+ int ret;
if (set & TIOCM_RTS) {
control |= CONTROL_RTS;
@@ -1231,6 +1237,27 @@ static int cp210x_tiocmset_port(struct usb_serial_port *port,
dev_dbg(&port->dev, "%s - control = 0x%.4x\n", __func__, control);
+ // Don't send MHS command if device in hardware flowcontrol mode
+ ret = cp210x_read_reg_block(port, CP210X_GET_FLOW, &flow_ctl, sizeof(flow_ctl));
+ if (ret)
+ return ret;
+
+ ctl_hs = le32_to_cpu(flow_ctl.ulControlHandshake);
+ flow_repl = le32_to_cpu(flow_ctl.ulFlowReplace);
+
+ if (CP210X_SERIAL_DTR_SHIFT(CP210X_SERIAL_DTR_FLOW_CTL) == (ctl_hs & CP210X_SERIAL_DTR_MASK))
+ auto_dtr = true;
+ else
+ auto_dtr = false;
+
+ if (CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_FLOW_CTL) == (flow_repl & CP210X_SERIAL_RTS_MASK))
+ auto_rts = true;
+ else
+ auto_rts = false;
+
+ if (auto_dtr || auto_rts)
+ return 0;
+
return cp210x_write_u16_reg(port, CP210X_SET_MHS, control);
}
--
2.17.1
