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 pin 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 <[email protected]> --- drivers/usb/serial/cp210x.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c index fbb10dfc56e3..1835ccf2aa2f 100644 --- a/drivers/usb/serial/cp210x.c +++ b/drivers/usb/serial/cp210x.c @@ -1211,6 +1211,11 @@ 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; if (set & TIOCM_RTS) { control |= CONTROL_RTS; @@ -1230,6 +1235,25 @@ 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 + cp210x_read_reg_block(port, CP210X_GET_FLOW, &flow_ctl, sizeof(flow_ctl)); + 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) { + dev_dbg(&port->dev, "Don't set MHS when while device in flow control mode\n"); + return 0; + } return cp210x_write_u16_reg(port, CP210X_SET_MHS, control); } -- 2.17.1
