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Subject[PATCH 3/7] coresight: Use event attributes for sink selection
Date
This patch uses the information conveyed by perf_event::attr::config2
to select a sink to use for the session. That way a sink can easily be
selected to be used by more than one source, something that isn't currently
possible with the sysfs implementation.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
.../hwtracing/coresight/coresight-etm-perf.c | 16 ++------
drivers/hwtracing/coresight/coresight-priv.h | 1 +
drivers/hwtracing/coresight/coresight.c | 39 +++++++++++++++++++
3 files changed, 44 insertions(+), 12 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index 292bd409a68c..685d16001d0b 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -201,18 +201,10 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
return NULL;
INIT_WORK(&event_data->work, free_event_data);

- /*
- * In theory nothing prevent tracers in a trace session from being
- * associated with different sinks, nor having a sink per tracer. But
- * until we have HW with this kind of topology we need to assume tracers
- * in a trace session are using the same sink. Therefore go through
- * the coresight bus and pick the first enabled sink.
- *
- * When operated from sysFS users are responsible to enable the sink
- * while from perf, the perf tools will do it based on the choice made
- * on the cmd line. As such the "enable_sink" flag in sysFS is reset.
- */
- sink = coresight_get_enabled_sink(true);
+ /* First get the selected sink from user space. */
+ sink = coresight_get_sink_by_id(event->attr.config2);
+ if (!sink)
+ sink = coresight_get_enabled_sink(true);
if (!sink || !sink_ops(sink)->alloc_buffer)
goto err;

diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
index 579f34943bf1..071bb98d358f 100644
--- a/drivers/hwtracing/coresight/coresight-priv.h
+++ b/drivers/hwtracing/coresight/coresight-priv.h
@@ -147,6 +147,7 @@ void coresight_disable_path(struct list_head *path);
int coresight_enable_path(struct list_head *path, u32 mode, void *sink_data);
struct coresight_device *coresight_get_sink(struct list_head *path);
struct coresight_device *coresight_get_enabled_sink(bool reset);
+struct coresight_device *coresight_get_sink_by_id(u64 id);
struct list_head *coresight_build_path(struct coresight_device *csdev,
struct coresight_device *sink);
void coresight_release_path(struct list_head *path);
diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
index 526f122a38ee..7e2ce0beb2a0 100644
--- a/drivers/hwtracing/coresight/coresight.c
+++ b/drivers/hwtracing/coresight/coresight.c
@@ -11,6 +11,7 @@
#include <linux/err.h>
#include <linux/export.h>
#include <linux/slab.h>
+#include <linux/stringhash.h>
#include <linux/mutex.h>
#include <linux/clk.h>
#include <linux/coresight.h>
@@ -541,6 +542,44 @@ struct coresight_device *coresight_get_enabled_sink(bool deactivate)
return dev ? to_coresight_device(dev) : NULL;
}

+static int coresight_sink_by_id(struct device *dev, void *data)
+{
+ struct coresight_device *csdev = to_coresight_device(dev);
+ unsigned long hash;
+
+ if (csdev->type == CORESIGHT_DEV_TYPE_SINK ||
+ csdev->type == CORESIGHT_DEV_TYPE_LINKSINK) {
+ /*
+ * See function etm_perf_sink_name_show() to know where this
+ * comes from.
+ */
+ hash = hashlen_hash(hashlen_string(NULL, dev_name(dev)));
+
+ if (hash == (*(unsigned long *)data))
+ return 1;
+ }
+
+ return 0;
+}
+
+/**
+ * coresight_get_sink_by_id - returns the sink that matches the id
+ * @id: Id of the sink to match
+ *
+ * The name of a sink is unique, whether it is found on the AMBA bus or
+ * otherwise. As such the hash of that name can easily be used to identify
+ * a sink.
+ */
+struct coresight_device *coresight_get_sink_by_id(u64 id)
+{
+ struct device *dev = NULL;
+
+ dev = bus_find_device(&coresight_bustype, NULL, &id,
+ coresight_sink_by_id);
+
+ return dev ? to_coresight_device(dev) : NULL;
+}
+
/*
* coresight_grab_device - Power up this device and any of the helper
* devices connected to it for trace operation. Since the helper devices
--
2.17.1
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