[PATCH v3 4/7] coresight: Use PMU driver configuration for sink selection

[Mathieu Poirier]

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@xxxxxxxxxx>
---
 drivers/hwtracing/coresight/coresight-etm-perf.c | 134 +++++++++++++++++++++--
 drivers/hwtracing/coresight/coresight-etm-perf.h |   4 +
 2 files changed, 126 insertions(+), 12 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index 2bbd3240ff72..5c23b35a8ad0 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -11,6 +11,7 @@
 #include <linux/list.h>
 #include <linux/mm.h>
 #include <linux/init.h>
+#include <linux/parser.h>
 #include <linux/perf_event.h>
 #include <linux/slab.h>
 #include <linux/types.h>
@@ -22,6 +23,8 @@
 static struct pmu etm_pmu;
 static bool etm_perf_up;
 
+#define CORESIGHT_DEVICE_MAX_NAME_LEN	256
+
 /**
  * struct etm_event_data - Coresight specifics associated to an event
  * @work:		Handle to free allocated memory outside IRQ context.
@@ -184,6 +187,78 @@ static void etm_free_aux(void *data)
 	schedule_work(&event_data->work);
 }
 
+static char *etm_drv_config_sync(struct perf_event *event)
+{
+	char *sink;
+	int node = event->cpu == -1 ? -1 : cpu_to_node(event->cpu);
+	struct pmu_drv_config *drv_config = perf_event_get_drv_config(event);
+
+	sink = kmalloc_node(CORESIGHT_DEVICE_MAX_NAME_LEN, GFP_KERNEL, node);
+	if (!sink)
+		return NULL;
+
+	/*
+	 * Make sure we don't race with perf_drv_config_replace() in
+	 * kernel/events/core.c.
+	 */
+	raw_spin_lock(&drv_config->lock);
+	memcpy(sink, drv_config->config, CORESIGHT_DEVICE_MAX_NAME_LEN);
+	raw_spin_unlock(&drv_config->lock);
+
+	return sink;
+}
+
+static struct coresight_device *etm_event_get_sink(struct perf_event *event)
+{
+	struct pmu_drv_config *drv_config = perf_event_get_drv_config(event);
+
+	/* CPU-wide scenarios aren't supported yet */
+	if (event->cpu != -1)
+		return NULL;
+
+	/*
+	 * Try the preferred method first, i.e getting the sink information
+	 * using the ioctl() method.
+	 */
+	if (drv_config->config) {
+		char *drv_config;
+		struct device *dev;
+		struct coresight_device *sink;
+
+		/*
+		 * Get sink from event->hw.drv_config.config - see
+		 * _perf_ioctl() _SET_DRV_CONFIG.
+		 */
+		drv_config = etm_drv_config_sync(event);
+		if (!drv_config)
+			goto out;
+
+		/* Look for the device of that name on the CS bus. */
+		dev = bus_find_device_by_name(&coresight_bustype, NULL,
+					      drv_config);
+		kfree(drv_config);
+
+		if (dev) {
+			sink = to_coresight_device(dev);
+			/* Put reference from 'bus_find_device()' */
+			put_device(dev);
+			return sink;
+		}
+	}
+
+	/*
+	 * No luck with the above method, so we are working with an older user
+	 * space.  See if a sink has been set using sysFS.  If this is the case
+	 * CPU-wide session will only be able to use a single 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.
+	 */
+out:
+	return coresight_get_enabled_sink(true);
+}
+
 static void *etm_setup_aux(struct perf_event *event, void **pages,
 			   int nr_pages, bool overwrite)
 {
@@ -197,18 +272,8 @@ 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 to use for this event */
+	sink = etm_event_get_sink(event);
 	if (!sink)
 		goto err;
 
@@ -445,6 +510,49 @@ static void etm_addr_filters_sync(struct perf_event *event)
 	filters->nr_filters = i;
 }
 
+static const match_table_t config_tokens = {
+	{ ETM_CFG_SINK,		"%u.%s" },
+	{ ETM_CFG_NONE,		NULL },
+};
+
+static void *etm_drv_config_validate(struct perf_event *event, char *cstr)
+{
+	char *str, *to_parse, *sink = NULL;
+	int token, ret = -EINVAL;
+	substring_t args[MAX_OPT_ARGS];
+
+	to_parse = kstrdup(cstr, GFP_KERNEL);
+	if (!to_parse)
+		return ERR_PTR(-ENOMEM);
+
+	while ((str = strsep(&to_parse, " ,\n")) != NULL) {
+		if (!*str)
+			continue;
+
+		token = match_token(str, config_tokens, args);
+		switch (token) {
+		case ETM_CFG_SINK:
+			sink = kstrdup(str, GFP_KERNEL);
+			if (!sink) {
+				ret = -ENOMEM;
+				goto out;
+			}
+			break;
+		default:
+			goto out;
+		}
+	}
+
+out:
+	kfree(to_parse);
+	return sink ? sink : ERR_PTR(ret);
+}
+
+static void etm_drv_config_free(void *drv_data)
+{
+	kfree(drv_data);
+}
+
 int etm_perf_symlink(struct coresight_device *csdev, bool link)
 {
 	char entry[sizeof("cpu9999999")];
@@ -489,6 +597,8 @@ 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;
+	etm_pmu.drv_config_free		= etm_drv_config_free;
 
 	ret = perf_pmu_register(&etm_pmu, CORESIGHT_ETM_PMU_NAME, -1);
 	if (ret == 0)
diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.h b/drivers/hwtracing/coresight/coresight-etm-perf.h
index 4197df4faf5e..37a98230fc34 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.h
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.h
@@ -42,6 +42,10 @@ struct etm_filters {
 	bool			ssstatus;
 };
 
+enum etm_config_elem_type {
+	ETM_CFG_NONE = -1,
+	ETM_CFG_SINK,
+};
 
 #ifdef CONFIG_CORESIGHT
 int etm_perf_symlink(struct coresight_device *csdev, bool link);
-- 
2.7.4