diff mbox series

[03/45] coresight: tmc-etf: Properly set AUX buffer head in snapshot mode

Message ID 20190619172949.4522-4-mathieu.poirier@linaro.org (mailing list archive)
State Mainlined, archived
Commit 0402f75efe4719bca950900275100d9a12f44a92
Headers show
Series coresight: next v5.2-rc5 | expand

Commit Message

Mathieu Poirier June 19, 2019, 5:29 p.m. UTC 
Unify amongst sink drivers how the AUX ring buffer head is communicated
to user space.  That way the same algorithm in user space 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>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Tested-by: Leo Yan <leo.yan@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);