diff mbox series

[V2,3/6] coresight: tmc-etf: Properly set AUX buffer head in snapshot mode

Message ID 20190514194018.23420-4-mathieu.poirier@linaro.org (mailing list archive)
State New, archived
Headers show
Series coresight: Fix snapshot mode | expand

Commit Message

Mathieu Poirier May 14, 2019, 7:40 p.m. UTC 
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-tmc-etf.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)
diff mbox series

Patch

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
index 2527b5d3b65e..d026bd04a6af 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
@@ -542,11 +542,15 @@  static unsigned long tmc_update_etf_buffer(struct coresight_device *csdev,
 		}
 	}
 
-	/* In snapshot mode we have to update the head */
-	if (buf->snapshot) {
-		handle->head = (cur * PAGE_SIZE) + offset;
-		to_read = buf->nr_pages << PAGE_SHIFT;
-	}
+	/*
+	 * 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 += to_read;
+
 	CS_LOCK(drvdata->base);
 out:
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);