From b1ffb4c851f185e9051ba837c16d9b84ef688d26 Mon Sep 17 00:00:00 2001 From: Andrew Worsley Date: Fri, 18 Nov 2011 23:13:33 +1100 Subject: [PATCH] USB: Fix Corruption issue in USB ftdi driver ftdi_sio.c 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 Cc: stable ---- 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 --- 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 8fe034d2d3e7..bd4298bb6750 100644 --- a/drivers/usb/serial/ftdi_sio.c +++ b/drivers/usb/serial/ftdi_sio.c @@ -2104,13 +2104,19 @@ 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; @@ -2151,6 +2157,7 @@ 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), @@ -2178,6 +2185,7 @@ 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, -- 2.30.2