coresight: etb10: adjust read pointer only when needed

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@arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
index 92f942321e1e..4d20b0be0c0b 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);
         }