[RFC PATCH 08/20] coresight: etb10: implementing buffer set and unset APIs

From: Mathieu Poirier
Date: Fri Sep 18 2015 - 12:31:44 EST


Implementing perf related APIs to activate and terminate
a trace session. More specifically dealing with the sink
buffer's internal mechanic along with perf's API to start
and stop interactions with the ring buffers.

Signed-off-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
---
drivers/hwtracing/coresight/coresight-etb10.c | 42 +++++++++++++++++++++++++++
include/linux/coresight.h | 8 +++++
2 files changed, 50 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
index ca2fbf65a454..3239036f4609 100644
--- a/drivers/hwtracing/coresight/coresight-etb10.c
+++ b/drivers/hwtracing/coresight/coresight-etb10.c
@@ -28,6 +28,7 @@
#include <linux/amba/bus.h>
#include <linux/clk.h>
#include <linux/mm.h>
+#include <linux/perf_event.h>

#include <asm/local.h>

@@ -306,10 +307,51 @@ static void *etb_setup_aux(struct coresight_device *csdev, int cpu,
return buf;
}

+static int etb_set_buffer(struct coresight_device *csdev,
+ struct perf_event *event,
+ struct perf_output_handle *handle)
+{
+ unsigned long head;
+ struct cs_buffers *buf;
+
+ buf = perf_aux_output_begin(handle, event);
+ if (!buf)
+ return -EINVAL;
+
+ /* how much space do we have in this session */
+ buf->size = handle->size;
+
+ /* wrap head around to the amount of space we have */
+ head = handle->head & ((buf->nr_pages << PAGE_SHIFT) - 1);
+
+ /* find the page to write to */
+ buf->cur = head / PAGE_SIZE;
+
+ /* and offset within that page */
+ buf->offset = head % PAGE_SIZE;
+
+ local_set(&buf->head, head);
+ local_set(&buf->data_size, 0);
+
+ return 0;
+}
+
+static void etb_unset_buffer(struct coresight_device *csdev,
+ struct perf_output_handle *handle)
+{
+ struct cs_buffers *buf = perf_get_aux(handle);
+
+ if (buf)
+ perf_aux_output_end(handle, local_xchg(&buf->data_size, 0),
+ local_xchg(&buf->lost, 0));
+}
+
static const struct coresight_ops_sink etb_sink_ops = {
.enable = etb_enable,
.disable = etb_disable,
.setup_aux = etb_setup_aux,
+ .set_buffer = etb_set_buffer,
+ .unset_buffer = etb_unset_buffer,
};

static const struct coresight_ops etb_cs_ops = {
diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index 71cc23709422..25bdce345ec3 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -15,6 +15,7 @@

#include <linux/device.h>
#include <linux/sched.h>
+#include <linux/perf_event.h>

/* Peripheral id registers (0xFD0-0xFEC) */
#define CORESIGHT_PERIPHIDR4 0xfd0
@@ -186,12 +187,19 @@ struct coresight_device {
* @enable: enables the sink.
* @disable: disables the sink.
* @setup_aux: initialises perf's ring buffer for trace collection.
+ * @set_buffer: initialises buffer mechanic before a trace session.
+ * @unset_buffer: finalises buffer mechanic after a trace session.
*/
struct coresight_ops_sink {
int (*enable)(struct coresight_device *csdev);
void (*disable)(struct coresight_device *csdev);
void *(*setup_aux)(struct coresight_device *csdev, int cpu,
void **pages, int nr_pages, bool overwrite);
+ int (*set_buffer)(struct coresight_device *csdev,
+ struct perf_event *event,
+ struct perf_output_handle *handle);
+ void (*unset_buffer)(struct coresight_device *csdev,
+ struct perf_output_handle *handle);
};

/**
--
1.9.1

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