MN10300: Introduce barriers to replace removed volatiles in gdbstub 16550 driver

Introduce into the MN10300 gdbstub 16550 driver a couple of barrier() calls to
replace the removed volatility of the input/output index variables for the Rx
ring buffer.  A previous patch added them into the on-chip serial port driver.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/mn10300/kernel/gdb-io-serial.c b/arch/mn10300/kernel/gdb-io-serial.c
index 9a6d4e8ebe73..11584c51acd9 100644
--- a/arch/mn10300/kernel/gdb-io-serial.c
+++ b/arch/mn10300/kernel/gdb-io-serial.c
@@ -99,6 +99,7 @@ int gdbstub_io_rx_char(unsigned char *_ch, int nonblock)
  try_again:
         /* pull chars out of the buffer */
         ix = gdbstub_rx_outp;
+        barrier();
         if (ix == gdbstub_rx_inp) {
                 if (nonblock)
                         return -EAGAIN;
@@ -110,6 +111,7 @@ int gdbstub_io_rx_char(unsigned char *_ch, int nonblock)
 
         ch = gdbstub_rx_buffer[ix++];
         st = gdbstub_rx_buffer[ix++];
+        barrier();
         gdbstub_rx_outp = ix & 0x00000fff;
 
         if (st & UART_LSR_BI) {