serial: st-asc: Ignore the parity error bit if 8-bit mode is enabled

The datasheet states:

"If the MODE field selects an 8-bit frame then this [parity error] bit
 is undefined. Software should ignore this bit when reading 8-bit frames."

Acked-by: Peter Griffin <peter.griffin@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/st-asc.c b/drivers/tty/serial/st-asc.c
index 379e5bd37df947013b71440333bc0d268936b5aa..69e62326723d644ba780f20b9c74472b10510263 100644 (file)
--- a/drivers/tty/serial/st-asc.c
+++ b/drivers/tty/serial/st-asc.c
@@ -287,9 +287,19 @@ static void asc_transmit_chars(struct uart_port *port)
 static void asc_receive_chars(struct uart_port *port)
 {
        struct tty_port *tport = &port->state->port;
-       unsigned long status;
+       unsigned long status, mode;
        unsigned long c = 0;
        char flag;
+       bool ignore_pe = false;
+
+       /*
+        * Datasheet states: If the MODE field selects an 8-bit frame then
+        * this [parity error] bit is undefined. Software should ignore this
+        * bit when reading 8-bit frames.
+        */
+       mode = asc_in(port, ASC_CTL) & ASC_CTL_MODE_MSK;
+       if (mode == ASC_CTL_MODE_8BIT || mode == ASC_CTL_MODE_8BIT_PAR)
+               ignore_pe = true;
 
        if (port->irq_wake)
                pm_wakeup_event(tport->tty->dev, 0);
@@ -299,8 +309,8 @@ static void asc_receive_chars(struct uart_port *port)
                flag = TTY_NORMAL;
                port->icount.rx++;
 
-               if ((c & (ASC_RXBUF_FE | ASC_RXBUF_PE)) ||
-                       status & ASC_STA_OE) {
+               if (status & ASC_STA_OE || c & ASC_RXBUF_FE ||
+                   (c & ASC_RXBUF_PE && !ignore_pe)) {
 
                        if (c & ASC_RXBUF_FE) {
                                if (c == (ASC_RXBUF_FE | ASC_RXBUF_DUMMY_RX)) {