[PATCH v2 1/3] USB: serial: cp210x: Fixed RTS mode setting by the CRTSCTS flag.

From: Konstantin Shkolnyy
Date: Fri Apr 29 2016 - 22:22:32 EST


A bug in the CRTSCTS handling caused RTS to alternate between
CRTSCTS=0 => "RTS transmits active signal" and
CRTSCTS=1 => "RTS receives flow control"
instead of
CRTSCTS=0 => "RTS is statically active" and
CRTSCTS=1 => "RTS receives flow control"
This only happened after first having enabled CRTSCTS.

Signed-off-by: Konstantin Shkolnyy <konstantin.shkolnyy@xxxxxxxxx>
---
Changes in v2:
Improved CRTSCTS fix based on feedback. Dropped get_termios error handling.

drivers/usb/serial/cp210x.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index dd47823..abcdb63 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -163,10 +163,6 @@ static const struct usb_device_id id_table[] = {
{ USB_DEVICE(0x1843, 0x0200) }, /* Vaisala USB Instrument Cable */
{ USB_DEVICE(0x18EF, 0xE00F) }, /* ELV USB-I2C-Interface */
{ USB_DEVICE(0x18EF, 0xE025) }, /* ELV Marble Sound Board 1 */
- { USB_DEVICE(0x1901, 0x0190) }, /* GE B850 CP2105 Recorder interface */
- { USB_DEVICE(0x1901, 0x0193) }, /* GE B650 CP2104 PMC interface */
- { USB_DEVICE(0x1901, 0x0194) }, /* GE Healthcare Remote Alarm Box */
- { USB_DEVICE(0x19CF, 0x3000) }, /* Parrot NMEA GPS Flight Recorder */
{ USB_DEVICE(0x1ADB, 0x0001) }, /* Schweitzer Engineering C662 Cable */
{ USB_DEVICE(0x1B1C, 0x1C00) }, /* Corsair USB Dongle */
{ USB_DEVICE(0x1BA4, 0x0002) }, /* Silicon Labs 358x factory default */
@@ -967,8 +963,7 @@ static void cp210x_set_termios(struct tty_struct *tty,
} else {
modem_ctl[0] &= ~0x7B;
modem_ctl[0] |= 0x01;
- /* FIXME - OR here instead of assignment looks wrong */
- modem_ctl[4] |= 0x40;
+ modem_ctl[4] = 0x40;
dev_dbg(dev, "%s - flow control = NONE\n", __func__);
}

--
1.8.4.5