Michael Hanselmann reports that
[a] subset of all CH341 devices stop responding to bulk
transfers, usually after the third byte, when the highest
prescaler bit (0b100) is set. There is one exception, namely a
prescaler of exactly 0b111 (fact=1, ps=3).
Fix this by forcing a lower base clock (fact = 0) whenever needed.
This specifically makes the standard rates 110, 134 and 200 bps work
again with these devices.
Fixes: 3571456508 ("USB: serial: ch341: reimplement line-speed handling")
Cc: stable <stable@vger.kernel.org> # 5.5
Reported-by: Michael Hanselmann <public@hansmi.ch>
Link: https://lore.kernel.org/r/20200514141743.GE25962@localhost
Signed-off-by: Johan Hovold <johan@kernel.org>
c432df1559