[PATCH] coresight: etb10: adjust read pointer only when needed

[Mathieu Poirier]

The read pointer (read_ptr) needs to be adjusted only if its value
has gone beyond the length of the memory buffer.

Reported-by: Suzuki K Poulose <suzuki.poulose at arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier at linaro.org>
---
 drivers/hwtracing/coresight/coresight-etb10.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
index 586c98fbdb03..1e4031ee8969 100644
--- a/drivers/hwtracing/coresight/coresight-etb10.c
+++ b/drivers/hwtracing/coresight/coresight-etb10.c
@@ -428,7 +428,8 @@ static void etb_update_buffer(struct coresight_device *csdev,
 		read_ptr = (write_ptr + drvdata->buffer_depth) -
 					to_read / ETB_FRAME_SIZE_WORDS;
 		/* Wrap around if need be*/
-		read_ptr &= ~(drvdata->buffer_depth - 1);
+		if (read_ptr > (drvdata->buffer_depth - 1))
+			read_ptr -= drvdata->buffer_depth;
 		/* let the decoder know we've skipped ahead */
 		local_inc(&buf->lost);
 	}
-- 
2.5.0