From b987edee414235e29984d424043761b735bb4a5e Mon Sep 17 00:00:00 2001 From: Andrew Worsley Date: Fri, 18 Nov 2011 23:13:33 +1100 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 --- drivers/usb/serial/ftdi_sio.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) (limited to 'drivers') diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c index 1b51d43..486769c 100644 --- a/drivers/usb/serial/ftdi_sio.c +++ b/drivers/usb/serial/ftdi_sio.c @@ -2080,13 +2080,19 @@ 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; @@ -2127,6 +2133,7 @@ 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), @@ -2154,6 +2161,7 @@ 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, -- cgit v1.1