serial: pxa: work around for errata #20

Errata E20: UART: Character Timeout interrupt remains set under certain
software conditions.

Implication: The software servicing the UART can be trapped in an infinite loop.

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 20 insertions, 0 deletions

diff --git a/drivers/tty/serial/pxa.c b/drivers/tty/serial/pxa.c
index 531931c1b250..5c8e3bba6c84 100644
--- a/drivers/tty/serial/pxa.c
+++ b/drivers/tty/serial/pxa.c
@@ -100,6 +100,16 @@ static inline void receive_chars(struct uart_pxa_port *up, int *status)
         int max_count = 256;
 
         do {
+                /* work around Errata #20 according to
+                 * Intel(R) PXA27x Processor Family
+                 * Specification Update (May 2005)
+                 *
+                 * Step 2
+                 * Disable the Reciever Time Out Interrupt via IER[RTOEI]
+                 */
+                up->ier &= ~UART_IER_RTOIE;
+                serial_out(up, UART_IER, up->ier);
+
                 ch = serial_in(up, UART_RX);
                 flag = TTY_NORMAL;
                 up->port.icount.rx++;
@@ -156,6 +166,16 @@ static inline void receive_chars(struct uart_pxa_port *up, int *status)
                 *status = serial_in(up, UART_LSR);
         } while ((*status & UART_LSR_DR) && (max_count-- > 0));
         tty_flip_buffer_push(tty);
+
+        /* work around Errata #20 according to
+         * Intel(R) PXA27x Processor Family
+         * Specification Update (May 2005)
+         *
+         * Step 6:
+         * No more data in FIFO: Re-enable RTO interrupt via IER[RTOIE]
+         */
+        up->ier |= UART_IER_RTOIE;
+        serial_out(up, UART_IER, up->ier);
 }
 
 static void transmit_chars(struct uart_pxa_port *up)