From b8bdad608213caffa081a97d2e937e5fe08c4046 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Frank=20Sch=C3=A4fer?= Date: Tue, 30 Jul 2013 21:49:04 +0200 Subject: [PATCH] USB: pl2303: restrict the divisor based baud rate encoding method to the "HX" chip type MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit It's not clear if the type_0 and type_1 chips support the divisor based baud rate encoding method, so don't use it until anyone with such chip has tested it to avoid regressions with the following patches. Even if it has been working fine with these chips since the code has been added 2 years ago, this change will not cause any regressions, because the baud rates currently supported/allowed with the divisor based method are supported with the direct method, too. The code for the divisor based method also isn't entirely correct (yet), so that the direct encoding method actually works better (sets the baud rate more precisely). Signed-off-by: Frank Schäfer Signed-off-by: Greg Kroah-Hartman --- drivers/usb/serial/pl2303.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/usb/serial/pl2303.c b/drivers/usb/serial/pl2303.c index 1e6de4cd079d..244820193e10 100644 --- a/drivers/usb/serial/pl2303.c +++ b/drivers/usb/serial/pl2303.c @@ -305,10 +305,14 @@ static void pl2303_encode_baudrate(struct tty_struct *tty, if (spriv->type != HX) baud = min_t(int, baud, 1228800); - if (baud <= 115200) { + if (spriv->type != HX || baud <= 115200) { + /* Direct (standard) baud rate encoding method */ put_unaligned_le32(baud, buf); } else { /* + * NOTE: it's not clear if the type_0/1 chips + * support this method + * * Apparently the formula for higher speeds is: * baudrate = 12M * 32 / (2^buf[1]) / buf[0] */ -- 2.20.1