If baud_divisor is not set (i.e. == -1), we should use the baud divisor already in use for flushing the xmit register. If we don't flush the xmit register, then SPL will hang.
Signed-off-by: Patrik Dahlström risca@dalakolonin.se --- drivers/serial/ns16550.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c index 754b6e9921..d9da7f799c 100644 --- a/drivers/serial/ns16550.c +++ b/drivers/serial/ns16550.c @@ -170,6 +170,13 @@ void NS16550_init(NS16550_t com_port, int baud_divisor) == UART_LSR_THRE) { if (baud_divisor != -1) NS16550_setbrg(com_port, baud_divisor); + else { + // Re-use old baud rate divisor to flush transmit reg. + const int dll = serial_in(&com_port->dll); + const int dlm = serial_in(&com_port->dlm); + const int divisor = dll | (dlm << 8); + NS16550_setbrg(com_port, divisor); + } serial_out(0, &com_port->mdr1); } #endif