max. baud rate available ?

[eddylai]

Is there any MAX. baud rate speed limitation?
I can set the baudrate to 921600 then connect correctly, (Ubuntu 16.04 Mono)
but once I set the baudrate to 1843200 or 2000000 got connect() errors like:

System.IO.IOException: Inappropriate ioctl for device
at SerialPortLib2.Port.SerialPortStream.ThrowIOException () [0x00013] in <76c0701fbbf54b82a7cf07603294b4f7>:0 System.IO.IOException: Inappropriate ioctl for device
at SerialPortLib2.Port.SerialPortStream.ThrowIOException () [0x00013] in <76c0701fbbf54b82a7cf07603294b4f7>:0
at SerialPortLib2.Port.SerialPortStream..ctor (System.String portName, System.Int32 baudRate, System.Int32 dataBits, SerialPortLib2.Port.Parity parity, SerialPortLib2.Port.StopBits stopBits, System.Boolean dtrEnable, System.Boolean rtsEnable, SerialPortLib2.Port.Handshake handshake, System.Int32 readTimeout, System.Int32 writeTimeout, System.Int32 readBufferSize, System.Int32 writeBufferSize, System.Boolean IsAVirtualPort) [0x00041] in <76c0701fbbf54b82a7cf07603294b4f7>:0
at (wrapper remoting-invoke-with-check) SerialPortLib2.Port.SerialPortStream..ctor(string,int,int,SerialPortLib2.Port.Parity,SerialPortLib2.Port.StopBits,bool,bool,SerialPortLib2.Port.Handshake,int,int,int,int,bool)
at SerialPortLib2.Port.SerialPort.Open () [0x00074] in <76c0701fbbf54b82a7cf07603294b4f7>:0
at (wrapper remoting-invoke-with-check) SerialPortLib2.Port.SerialPort.Open()
at SerialPortLib2.SerialPortInput.Open () [0x0010c] in <76c0701fbbf54b82a7cf07603294b4f7>:0
at SerialPortLib2.Port.SerialPortStream..ctor (System.String portName, System.Int32 baudRate, System.Int32 dataBits, SerialPortLib2.Port.Parity parity, SerialPortLib2.Port.StopBits stopBits, System.Boolean dtrEnable, System.Boolean rtsEnable, SerialPortLib2.Port.Handshake handshake, System.Int32 readTimeout, System.Int32 writeTimeout, System.Int32 readBufferSize, System.Int32 writeBufferSize, System.Boolean IsAVirtualPort) [0x00041] in <76c0701fbbf54b82a7cf07603294b4f7>:0
at (wrapper remoting-invoke-with-check) SerialPortLib2.Port.SerialPortStream..ctor(string,int,int,SerialPortLib2.Port.Parity,SerialPortLib2.Port.StopBits,bool,bool,SerialPortLib2.Port.Handshake,int,int,int,int,bool)
at SerialPortLib2.Port.SerialPort.Open () [0x00074] in <76c0701fbbf54b82a7cf07603294b4f7>:0
at (wrapper remoting-invoke-with-check) SerialPortLib2.Port.SerialPort.Open()
at SerialPortLib2.SerialPortInput.Open () [0x0010c] in <76c0701fbbf54b82a7cf07603294b4f7>:0