http://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/?id=552f6bf1bb0eda0011c0525dd587aa9e7ba5b846 From 552f6bf1bb0eda0011c0525dd587aa9e7ba5b846 Mon Sep 17 00:00:00 2001 From: Andrew Worsley Date: Fri, 18 Nov 2011 12:13:33 +0000 Subject: USB: Fix Corruption issue in USB ftdi driver ftdi_sio.c 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 Signed-off-by: Greg Kroah-Hartman --- --- linux-2.6.28/drivers/usb/serial/ftdi_sio.c +++ linux-2.6.28/drivers/usb/serial/ftdi_sio.c @@ -2197,13 +2197,19 @@ 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 */ termios->c_cflag &= ~CMSPAR; @@ -2240,6 +2246,7 @@ } /* 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), @@ -2265,6 +2272,7 @@ /* 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,