coresight: etm-perf: incorporating sink definition from the cmd line

Now that PMU specific configuration is available as part of the event,
lookup the sink identified by users from the perf command line and build
a path from source to sink.

With this functionality it is no longer required to select a sink in a
separate step (from sysFS) before a perf trace session can be started.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

Author: mathieupoirier

drivers/hwtracing/coresight/coresight-etm-perf.c

@@ -22,6 +22,7 @@
 #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>
@@ -46,6 +47,17 @@ struct etm_event_data {
 	struct list_head **path;
 };
 
+/**
+ * struct perf_pmu_drv_config - Driver specific configuration needed
+ *				before a session can start.
+ * @sink:		The name of the sink this session should use.
+ * @entry:		Hook to the event->drv_configs list.
+ */
+struct perf_pmu_drv_config {
+	char *sink;
+	struct list_head entry;
+};
+
 static DEFINE_PER_CPU(struct perf_output_handle, ctx_handle);
 static DEFINE_PER_CPU(struct coresight_device *, csdev_src);
 
@@ -159,9 +171,22 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
 			   int nr_pages, bool overwrite)
 {
 	int cpu;
+	char *sink_def = NULL;
 	cpumask_t *mask;
 	struct coresight_device *sink;
 	struct etm_event_data *event_data = NULL;
+	struct perf_pmu_drv_config *drv_config;
+
+	/*
+	 * Search the driver configurables looking for a sink.  If more than
+	 * one sink was specified the last one is taken.
+	 */
+	list_for_each_entry(drv_config, &event->drv_configs, entry) {
+		if (drv_config && drv_config->sink) {
+			sink_def = drv_config->sink;
+			break;
+		}
+	}
 
 	event_data = alloc_event_data(event->cpu);
 	if (!event_data)
@@ -184,7 +209,7 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
 		 * list of devices from source to sink that can be
 		 * referenced later when the path is actually needed.
 		 */
-		event_data->path[cpu] = coresight_build_path(csdev, NULL);
+		event_data->path[cpu] = coresight_build_path(csdev, sink_def);
 		if (!event_data->path[cpu])
 			goto err;
 	}
@@ -342,6 +367,95 @@ static void etm_event_del(struct perf_event *event, int mode)
 	etm_event_stop(event, PERF_EF_UPDATE);
 }
 
+enum {
+	ETM_TOKEN_SINK_CPU,
+	ETM_TOKEN_SINK,
+	ETM_TOKEN_ERR,
+};
+
+static const match_table_t drv_cfg_tokens = {
+	{ETM_TOKEN_SINK_CPU, "sink=cpu%d:%s"},
+	{ETM_TOKEN_SINK, "sink=%s"},
+	{ETM_TOKEN_ERR,	NULL},
+};
+
+static int etm_get_drv_configs(struct perf_event *event, void __user *arg)
+{
+	char *config, *sink = NULL;
+	int cpu = -1, token, ret = 0;
+	substring_t args[MAX_OPT_ARGS];
+	struct perf_pmu_drv_config *drv_config = NULL;
+
+	/* Make user supplied input usable */
+	config = strndup_user(arg, PAGE_SIZE);
+	if (IS_ERR(config))
+		return PTR_ERR(config);
+
+	/* See above declared @drv_cfg_tokens for the usable formats */
+	token = match_token(config, drv_cfg_tokens, args);
+	switch (token) {
+	case ETM_TOKEN_SINK:
+		/* Just a sink has been specified */
+		sink = match_strdup(&args[0]);
+		if (IS_ERR(sink)) {
+			ret = PTR_ERR(sink);
+			goto err;
+		}
+		break;
+	case ETM_TOKEN_SINK_CPU:
+		/* We have a sink and a CPU */
+		if (match_int(&args[0], &cpu)) {
+			ret = -EINVAL;
+			goto err;
+		}
+		sink = match_strdup(&args[1]);
+		if (IS_ERR(sink)) {
+			ret = PTR_ERR(sink);
+			goto err;
+		}
+		break;
+	default:
+		ret = -EINVAL;
+		goto err;
+	}
+
+	/* If the CPUs don't match the sink is destined to another path */
+	if (event->cpu != cpu)
+		goto err;
+
+	/*
+	 * We have a valid configuration, allocate memory and add to the list
+	 * of driver configurables.
+	 */
+	drv_config = kzalloc(sizeof(*drv_config), GFP_KERNEL);
+	if (IS_ERR(drv_config)) {
+		ret = PTR_ERR(drv_config);
+		goto err;
+	}
+
+	drv_config->sink = sink;
+	list_add(&drv_config->entry, &event->drv_configs);
+
+out:
+	kfree(config);
+	return ret;
+
+err:
+	kfree(sink);
+	goto out;
+}
+
+static void etm_free_drv_configs(struct perf_event *event)
+{
+	struct perf_pmu_drv_config *config, *itr;
+
+	list_for_each_entry_safe(config, itr, &event->drv_configs, entry) {
+		list_del(&config->entry);
+		kfree(config->sink);
+		kfree(config);
+	}
+}
+
 int etm_perf_symlink(struct coresight_device *csdev, bool link)
 {
 	char entry[sizeof("cpu9999999")];
@@ -383,6 +497,9 @@ static int __init etm_perf_init(void)
 	etm_pmu.stop		= etm_event_stop;
 	etm_pmu.add		= etm_event_add;
 	etm_pmu.del		= etm_event_del;
+	etm_pmu.get_drv_configs	= etm_get_drv_configs;
+	etm_pmu.free_drv_configs
+				= etm_free_drv_configs;
 
 	ret = perf_pmu_register(&etm_pmu, CORESIGHT_ETM_PMU_NAME, -1);
 	if (ret == 0)