From: Andrew Worsley <amwors...@gmail.com>
-------------------
This is a commit scheduled for the next v2.6.34 longterm release.
http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
If you see a problem with using this for longterm, please comment.
-------------------
commit b1ffb4c851f185e9051ba837c16d9b84ef688d26 upstream.
Fix for ftdi_set_termios() glitching output
ftdi_set_termios() is constantly setting the baud rate, data bits and parity
unnecessarily on every call, . When called while characters are being
transmitted can cause the FTDI chip to corrupt the serial port bit stream
output by stalling the output half a bit during the output of a character.
Simple fix by skipping this setting if the baud rate/data bits/parity are
unchanged.
Signed-off-by: Andrew Worsley <amwors...@gmail.com>
----
I had a brief run with strace on the getty and it was doing ioctl()s on
each call but it didn't look relavant to the problem. I think the issue is
that XON/XOFF flow control was being implmented via hardware - for the ixoff
to allow the user to use XON/XOFF to control output. Unfortunately it would
send 3 Control URBs updating all of the settings after each piece of input
I am trying to work around the issue of gmail messing with the tab/spacing
by submitting via SMTP via gmail which I believe should fix the issue.
The patch is against v3.2-rc2 and compiles - but no additional testing in
this kernel has been done.
Thanks
Andrew
Signed-off-by: Greg Kroah-Hartman <gre...@suse.de>
Signed-off-by: Paul Gortmaker <paul.gortma...@windriver.com>
---
drivers/usb/serial/ftdi_sio.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 24dc63c..7367f4b 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -2332,13 +2332,19 @@ static void ftdi_set_termios(struct tty_struct *tty,
cflag = termios->c_cflag;
- /* FIXME -For this cut I don't care if the line is really changing or
- not - so just do the change regardless - should be able to
- compare old_termios and tty->termios */
+ if (old_termios->c_cflag == termios->c_cflag
+ && old_termios->c_ispeed == termios->c_ispeed
+ && old_termios->c_ospeed == termios->c_ospeed)
+ goto no_c_cflag_changes;
+
/* NOTE These routines can get interrupted by
ftdi_sio_read_bulk_callback - need to examine what this means -
don't see any problems yet */
+ if ((old_termios->c_cflag & (CSIZE|PARODD|PARENB|CMSPAR|CSTOPB)) ==
+ (termios->c_cflag & (CSIZE|PARODD|PARENB|CMSPAR|CSTOPB)))
+ goto no_data_parity_stop_changes;
+
/* Set number of data bits, parity, stop bits */
urb_value = 0;
@@ -2379,6 +2385,7 @@ static void ftdi_set_termios(struct tty_struct *tty,
}
/* Now do the baudrate */
+no_data_parity_stop_changes:
if ((cflag & CBAUD) == B0) {
/* Disable flow control */
if (usb_control_msg(dev, usb_sndctrlpipe(dev, 0),
@@ -2406,6 +2413,7 @@ static void ftdi_set_termios(struct tty_struct *tty,
/* Set flow control */
/* Note device also supports DTR/CD (ugh) and Xon/Xoff in hardware */
+no_c_cflag_changes:
if (cflag & CRTSCTS) {
dbg("%s Setting to CRTSCTS flow control", __func__);
if (usb_control_msg(dev,
--
1.7.12.rc2
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
