"fix baud rate handling in case of unsupported values"
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/usb/serial/pl2303.c?id=25b8286805e856c8c7fda127018e31032c918015
but I only can test it with 500000.
Patch made against mainline but tested with 3.4.45