linux-kernel - [PATCH V2 6/6] coresight: etm-perf: incorporating sink definition from cmd line

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Message-Id: <1469047100-18131-7-git-send-email-mathieu.poirier@linaro.org>
Date:	Wed, 20 Jul 2016 14:38:20 -0600
From:	Mathieu Poirier <mathieu.poirier@...aro.org>
To:	acme@...nel.org, jolsa@...nel.org
Cc:	peterz@...radead.org, mingo@...hat.com,
	alexander.shishkin@...ux.intel.com, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: [PATCH V2 6/6] coresight: etm-perf: incorporating sink definition from 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@...aro.org>
---
 drivers/hwtracing/coresight/coresight-etm-perf.c | 101 ++++++++++++++++++++++-
 1 file changed, 100 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index f8c7a8733b23..5658a7411a66 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/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>
@@ -71,11 +72,20 @@ static const struct attribute_group *etm_pmu_attr_groups[] = {
 
 static void etm_event_read(struct perf_event *event) {}
 
+static void etm_event_destroy(struct perf_event *event)
+{
+	kfree(event->hw.drv_configs);
+	event->hw.drv_configs = NULL;
+}
+
 static int etm_event_init(struct perf_event *event)
 {
 	if (event->attr.type != etm_pmu.type)
 		return -ENOENT;
 
+	event->destroy = etm_event_destroy;
+	event->hw.drv_configs = NULL;
+
 	return 0;
 }
 
@@ -159,6 +169,7 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
 			   int nr_pages, bool overwrite)
 {
 	int cpu;
+	char *cmdl_sink;
 	cpumask_t *mask;
 	struct coresight_device *sink;
 	struct etm_event_data *event_data = NULL;
@@ -171,6 +182,12 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
 
 	mask = &event_data->mask;
 
+	/*
+	 * If a sink was specified from the perf cmdline it will be part of
+	 * the event's drv_configs.
+	 */
+	cmdl_sink = (char *)event->hw.drv_configs;
+
 	/* Setup the path for each CPU in a trace session */
 	for_each_cpu(cpu, mask) {
 		struct coresight_device *csdev;
@@ -184,7 +201,7 @@ 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, cmdl_sink);
 		if (!event_data->path[cpu])
 			goto err;
 	}
@@ -342,6 +359,87 @@ 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_set_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];
+
+	/* Only one sink per event */
+	if (event->hw.drv_configs != NULL) {
+		ret = -EINVAL;
+		goto err;
+	}
+
+	/* Make user supplied input usable */
+	config = strndup_user(arg, PAGE_SIZE);
+	if (IS_ERR(config)) {
+		ret = PTR_ERR(config);
+		goto err;
+	}
+
+	/* 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 */
+
+		/* First get the cpu */
+		if (match_int(&args[0], &cpu)) {
+			ret = -EINVAL;
+			goto err;
+		}
+
+		/* Then the sink */
+		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.  This
+	 * isn't as an error hence not setting @ret.
+	 */
+	if (event->cpu != cpu)
+		goto err;
+
+	/* We have a valid configuration */
+	event->hw.drv_configs = sink;
+
+out:
+	return ret;
+
+err:
+	kfree(sink);
+	goto out;
+}
+
 int etm_perf_symlink(struct coresight_device *csdev, bool link)
 {
 	char entry[sizeof("cpu9999999")];
@@ -383,6 +481,7 @@ 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.set_drv_configs	= etm_set_drv_configs;
 
 	ret = perf_pmu_register(&etm_pmu, CORESIGHT_ETM_PMU_NAME, -1);
 	if (ret == 0)
-- 
2.7.4