[PATCH 1/5] coresight: Fix buffer size in snapshot mode

[Mathieu Poirier <mathieu.poirier@linaro.org>]

In snapshot mode the buffer used by the sink devices need to be
equal to the ring buffer size in order for the user space mechanic
to work properly.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 drivers/hwtracing/coresight/coresight-etb10.c | 23 +++++++++++++++++++
 .../hwtracing/coresight/coresight-tmc-etf.c   | 20 ++++++++++++++++
 .../hwtracing/coresight/coresight-tmc-etr.c   |  8 +++++--
 3 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
index 4ee4c80a4354..0764647b92bc 100644
--- a/drivers/hwtracing/coresight/coresight-etb10.c
+++ b/drivers/hwtracing/coresight/coresight-etb10.c
@@ -374,7 +374,30 @@ static void *etb_alloc_buffer(struct coresight_device *csdev,
 			      int nr_pages, bool overwrite)
 {
 	int node, cpu = event->cpu;
+	u32 capacity;
 	struct cs_buffers *buf;
+	struct etb_drvdata *drvdata;
+
+	/*
+	 * In snapsot mode the size of the perf ring buffer needs to be equal
+	 * to the size of the device's internal memory if we want to reuse the
+	 * generic AUX buffer management mechanic.
+	 *
+	 * For example (assuming 4096 byte page size):
+	 *
+	 *    # cat /sys/bus/coresight/devices/20010000.etb/mgmt/rdp
+	 *    0x2000
+	 *    # perf record -e cs_etm/@20010000.etf/ -S -m,8 --per-thread $APP
+	 *
+	 */
+	drvdata = dev_get_drvdata(csdev->dev.parent);
+	capacity = drvdata->buffer_depth * ETB_FRAME_SIZE_WORDS;
+
+	if (overwrite &&
+	    ((nr_pages << PAGE_SHIFT) != capacity)) {
+		dev_err(&csdev->dev, "Ring buffer not equal to device buffer");
+		return NULL;
+	}
 
 	if (cpu == -1)
 		cpu = smp_processor_id();
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
index 2527b5d3b65e..7694833b13cb 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
@@ -380,6 +380,26 @@ static void *tmc_alloc_etf_buffer(struct coresight_device *csdev,
 {
 	int node, cpu = event->cpu;
 	struct cs_buffers *buf;
+	struct tmc_drvdata *drvdata;
+
+	/*
+	 * In snapsot mode the size of the perf ring buffer needs to be equal
+	 * to the size of the device's internal memory if we want to reuse the
+	 * generic AUX buffer management mechanic.
+	 *
+	 * For example (assuming 4096 byte page size):
+	 *
+	 *    # cat /sys/bus/coresight/devices/20010000.etf/buffer_size
+	 *    0x10000
+	 *    # perf record -e cs_etm/@20010000.etf/ -S -m,16 --per-thread $APP
+	 *
+	 */
+	drvdata = dev_get_drvdata(csdev->dev.parent);
+	if (overwrite &&
+	    ((nr_pages << PAGE_SHIFT) != drvdata->size)) {
+		dev_err(&csdev->dev, "Ring buffer not equal to device buffer");
+		return NULL;
+	}
 
 	if (cpu == -1)
 		cpu = smp_processor_id();
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index df6e4b0b84e9..b9881d6d41ba 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -1188,9 +1188,13 @@ alloc_etr_buf(struct tmc_drvdata *drvdata, struct perf_event *event,
 
 	/*
 	 * Try to match the perf ring buffer size if it is larger
-	 * than the size requested via sysfs.
+	 * than the size requested via sysfs.  In snapsot mode the size
+	 * of the perf ring buffer needs to be equal to the allocated
+	 * size if we want to reuse the generic AUX buffer management
+	 * mechanic.
 	 */
-	if ((nr_pages << PAGE_SHIFT) > drvdata->size) {
+	if (snapshot ||
+	    (nr_pages << PAGE_SHIFT) > drvdata->size) {
 		etr_buf = tmc_alloc_etr_buf(drvdata, (nr_pages << PAGE_SHIFT),
 					    0, node, NULL);
 		if (!IS_ERR(etr_buf))
-- 
2.17.1


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