[PATCH V2 1/6] coresight: etb10: Properly set AUX buffer head in snapshot mode

Mathieu Poirier
2019-05-14T19:40:38Z

Unify amongst sink drivers how the AUX ring buffer head is communicated
to user space. That way the same algorithm in cs_etm_find_snapshot()
can be used to determine where the latest data is and how much of it
to access.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
drivers/hwtracing/coresight/coresight-etb10.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
index 4ee4c80a4354..60e753b1768d 100644
--- a/drivers/hwtracing/coresight/coresight-etb10.c
+++ b/drivers/hwtracing/coresight/coresight-etb10.c
@@ -548,13 +548,14 @@ static unsigned long etb_update_buffer(struct coresight_device *csdev,
writel_relaxed(0x0, drvdata->base + ETB_RAM_WRITE_POINTER);

/*
- * In snapshot mode we have to update the handle->head to point
- * to the new location.
+ * In snapshot mode we simply increment the head by the number of byte
+ * that were written. User space function cs_etm_find_snapshot() will
+ * figure out how many bytes to get from the AUX buffer based on the
+ * position of the head.
*/
- if (buf->snapshot) {
- handle->head = (cur * PAGE_SIZE) + offset;
- to_read = buf->nr_pages << PAGE_SHIFT;
- }
+ if (buf->snapshot)
+ handle->head += to_read;
+
__etb_enable_hw(drvdata);
CS_LOCK(drvdata->base);
out:
--
2.17.1