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Subject[PATCH v5 4/6] coresight: Use PMU driver configuration for sink selection
Date
This patch uses the PMU driver configuration held in event::hw::drv_config
to select a sink for each event that is created (the old sysFS way of
working is kept around for backward compatibility).

By proceeding in this way a sink can be used by multiple sessions
without having to play games with entries in sysFS.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
drivers/hwtracing/coresight/coresight-etm-perf.c | 74 ++++++++++++++++++++----
1 file changed, 62 insertions(+), 12 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index f21eb28b6782..a7e1fdef07f2 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -4,6 +4,7 @@
* Author: Mathieu Poirier <mathieu.poirier@linaro.org>
*/

+#include <linux/amba/bus.h>
#include <linux/coresight.h>
#include <linux/coresight-pmu.h>
#include <linux/cpumask.h>
@@ -11,6 +12,7 @@
#include <linux/list.h>
#include <linux/mm.h>
#include <linux/init.h>
+#include <linux/ioport.h>
#include <linux/perf_event.h>
#include <linux/percpu-defs.h>
#include <linux/slab.h>
@@ -177,6 +179,26 @@ static void etm_free_aux(void *data)
schedule_work(&event_data->work);
}

+static struct coresight_device *etm_drv_config_sync(struct perf_event *event)
+{
+ struct coresight_device *sink = NULL;
+ struct pmu_drv_config *drv_config = perf_event_get_drv_config(event);
+
+ /*
+ * Make sure we don't race with perf_drv_config_replace() in
+ * kernel/events/core.c.
+ */
+ raw_spin_lock(&drv_config->lock);
+
+ /* Copy what we got from user space if applicable. */
+ if (drv_config->config)
+ sink = drv_config->config;
+
+ raw_spin_unlock(&drv_config->lock);
+
+ return sink;
+}
+
static void *etm_setup_aux(struct perf_event *event, void **pages,
int nr_pages, bool overwrite)
{
@@ -190,18 +212,11 @@ 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 sink config from user space. */
+ sink = etm_drv_config_sync(event);
+ if (!sink)
+ sink = coresight_get_enabled_sink(true);
+
if (!sink || !sink_ops(sink)->alloc_buffer)
goto err;

@@ -454,6 +469,40 @@ static void etm_addr_filters_sync(struct perf_event *event)
filters->nr_filters = i;
}

+static int etm_drv_config_find_sink(struct device *dev, void *data)
+{
+ struct amba_device *adev = to_amba_device(dev->parent);
+ struct resource *res = &adev->res;
+ u64 value = *((u64 *)data);
+
+ /*
+ * The HW mapping of a component is unique. If the value we've been
+ * given matches the component's start address, then we must have found
+ * the device we are looking for.
+ */
+ if (res->start == value)
+ return 1;
+
+ return 0;
+}
+
+static void *etm_drv_config_validate(struct perf_event *event, u64 value)
+{
+ struct device *dev;
+ struct coresight_device *sink;
+
+ /* Look for the device with a res->start equal to @value. */
+ dev = bus_find_device(&coresight_bustype, NULL,
+ &value, etm_drv_config_find_sink);
+ if (!dev)
+ return ERR_PTR(-EINVAL);
+
+ sink = to_coresight_device(dev);
+ put_device(dev);
+
+ return sink;
+}
+
int etm_perf_symlink(struct coresight_device *csdev, bool link)
{
char entry[sizeof("cpu9999999")];
@@ -498,6 +547,7 @@ static int __init etm_perf_init(void)
etm_pmu.addr_filters_sync = etm_addr_filters_sync;
etm_pmu.addr_filters_validate = etm_addr_filters_validate;
etm_pmu.nr_addr_filters = ETM_ADDR_CMP_MAX;
+ etm_pmu.drv_config_validate = etm_drv_config_validate;

ret = perf_pmu_register(&etm_pmu, CORESIGHT_ETM_PMU_NAME, -1);
if (ret == 0)
--
2.7.4
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