| From b1ffb4c851f185e9051ba837c16d9b84ef688d26 Mon Sep 17 00:00:00 2001 |
| From: Andrew Worsley <amworsley@gmail.com> |
| Date: Fri, 18 Nov 2011 23:13:33 +1100 |
| Subject: USB: Fix Corruption issue in USB ftdi driver ftdi_sio.c |
| |
| From: Andrew Worsley <amworsley@gmail.com> |
| |
| 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 <amworsley@gmail.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> |
| |
| --- |
| drivers/usb/serial/ftdi_sio.c | 14 +++++++++++--- |
| 1 file changed, 11 insertions(+), 3 deletions(-) |
| |
| --- 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_ |
| |
| 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_ |
| } |
| |
| /* 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_ |
| |
| /* 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, |
