serial/arc-uart: Handle Rx Error Interrupts w/o any data

Currently, Rx error handling only triggers if there is some Rx data.
Fix that by checking for error - before the data handling.

Reported-by: Mischa Jonker <mjonker@synopsys.com>
Tested-by: Mischa Jonker <mjonker@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 16 insertions, 10 deletions

diff --git a/drivers/tty/serial/arc_uart.c b/drivers/tty/serial/arc_uart.c
index 2f195f0d7a11..e296c892df61 100644
--- a/drivers/tty/serial/arc_uart.c
+++ b/drivers/tty/serial/arc_uart.c
@@ -209,9 +209,9 @@ static void arc_serial_start_tx(struct uart_port *port)
         arc_serial_tx_chars(uart);
 }
 
-static void arc_serial_rx_chars(struct arc_uart_port *uart)
+static void arc_serial_rx_chars(struct arc_uart_port *uart, unsigned int status)
 {
-        unsigned int status, ch, flg = 0;
+        unsigned int ch, flg = 0;
 
         /*
          * UART has 4 deep RX-FIFO. Driver's recongnition of this fact
@@ -222,11 +222,11 @@ static void arc_serial_rx_chars(struct arc_uart_port *uart)
          * before RX-EMPTY=0, implies some sort of buffering going on in the
          * controller, which is indeed the Rx-FIFO.
          */
-        while (!((status = UART_GET_STATUS(uart)) & RXEMPTY)) {
-
-                ch = UART_GET_DATA(uart);
-                uart->port.icount.rx++;
-
+        do {
+                /*
+                 * This could be an Rx Intr for err (no data),
+                 * so check err and clear that Intr first
+                 */
                 if (unlikely(status & (RXOERR | RXFERR))) {
                         if (status & RXOERR) {
                                 uart->port.icount.overrun++;
@@ -242,6 +242,12 @@ static void arc_serial_rx_chars(struct arc_uart_port *uart)
                 } else
                         flg = TTY_NORMAL;
 
+                if (status & RXEMPTY)
+                        continue;
+
+                ch = UART_GET_DATA(uart);
+                uart->port.icount.rx++;
+
                 if (unlikely(uart_handle_sysrq_char(&uart->port, ch)))
                         goto done;
 
@@ -249,7 +255,7 @@ static void arc_serial_rx_chars(struct arc_uart_port *uart)
 
 done:
                 tty_flip_buffer_push(&uart->port.state->port);
-        }
+        } while (!((status = UART_GET_STATUS(uart)) & RXEMPTY));
 }
 
 /*
@@ -292,11 +298,11 @@ static irqreturn_t arc_serial_isr(int irq, void *dev_id)
          * notifications from the UART Controller.
          * To demultiplex between the two, we check the relevant bits
          */
-        if ((status & RXIENB) && !(status & RXEMPTY)) {
+        if (status & RXIENB) {
 
                 /* already in ISR, no need of xx_irqsave */
                 spin_lock(&uart->port.lock);
-                arc_serial_rx_chars(uart);
+                arc_serial_rx_chars(uart, status);
                 spin_unlock(&uart->port.lock);
         }