[PATCH 14/17] coresight: Use per-sink trace ID maps for Perf sessions

[James Clark]

This will allow sessions with more than CORESIGHT_TRACE_IDS_MAX ETMs
as long as there are fewer than that many ETMs connected to each sink.

Each sink owns its own trace ID map, and any Perf session connecting to
that sink will allocate from it, even if the sink is currently in use by
other users. This is similar to the existing behavior where the dynamic
trace IDs are constant as long as there is any concurrent Perf session
active. It's not completely optimal because slightly more IDs will be
used than necessary, but the optimal solution involves tracking the PIDs
of each session and allocating ID maps based on the session owner. This
is difficult to do with the combination of per-thread and per-cpu modes
and some scheduling issues. The complexity of this isn't likely to worth
it because even with multiple users they'd just see a difference in the
ordering of ID allocations rather than hitting any limits (unless the
hardware does have too many ETMs connected to one sink).

Signed-off-by: James Clark <james.clark at arm.com>
---
 drivers/hwtracing/coresight/coresight-core.c     | 10 ++++++++++
 drivers/hwtracing/coresight/coresight-etm-perf.c | 15 ++++++++-------
 include/linux/coresight.h                        |  1 +
 3 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index 9fc6f6b863e0..d1adff467670 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -902,6 +902,7 @@ static void coresight_device_release(struct device *dev)
 	struct coresight_device *csdev = to_coresight_device(dev);
 
 	fwnode_handle_put(csdev->dev.fwnode);
+	free_percpu(csdev->perf_id_map.cpu_map);
 	kfree(csdev);
 }
 
@@ -1159,6 +1160,14 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
 	csdev->dev.fwnode = fwnode_handle_get(dev_fwnode(desc->dev));
 	dev_set_name(&csdev->dev, "%s", desc->name);
 
+	if (csdev->type == CORESIGHT_DEV_TYPE_SINK ||
+	    csdev->type == CORESIGHT_DEV_TYPE_LINKSINK) {
+		csdev->perf_id_map.cpu_map = alloc_percpu(atomic_t);
+		if (!csdev->perf_id_map.cpu_map) {
+			ret = -ENOMEM;
+			goto err_out;
+		}
+	}
 	/*
 	 * Make sure the device registration and the connection fixup
 	 * are synchronised, so that we don't see uninitialised devices
@@ -1216,6 +1225,7 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
 err_out:
 	/* Cleanup the connection information */
 	coresight_release_platform_data(NULL, desc->dev, desc->pdata);
+	kfree(csdev);
 	return ERR_PTR(ret);
 }
 EXPORT_SYMBOL_GPL(coresight_register);
diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index 177cecae38d9..86ca1a9d09a7 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -229,10 +229,13 @@ static void free_event_data(struct work_struct *work)
 		struct list_head **ppath;
 
 		ppath = etm_event_cpu_path_ptr(event_data, cpu);
-		if (!(IS_ERR_OR_NULL(*ppath)))
+		if (!(IS_ERR_OR_NULL(*ppath))) {
+			struct coresight_device *sink = coresight_get_sink(*ppath);
+
+			coresight_trace_id_put_cpu_id(cpu, &sink->perf_id_map);
 			coresight_release_path(*ppath);
+		}
 		*ppath = NULL;
-		coresight_trace_id_put_cpu_id(cpu, coresight_trace_id_map_default());
 	}
 
 	/* mark perf event as done for trace id allocator */
@@ -401,8 +404,7 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
 		}
 
 		/* ensure we can allocate a trace ID for this CPU */
-		trace_id = coresight_trace_id_get_cpu_id(cpu,
-							 coresight_trace_id_map_default());
+		trace_id = coresight_trace_id_get_cpu_id(cpu, &sink->perf_id_map);
 		if (!IS_VALID_CS_TRACE_ID(trace_id)) {
 			cpumask_clear_cpu(cpu, mask);
 			coresight_release_path(path);
@@ -497,7 +499,7 @@ static void etm_event_start(struct perf_event *event, int flags)
 
 	/* Finally enable the tracer */
 	if (source_ops(csdev)->enable(csdev, event, CS_MODE_PERF,
-				      coresight_trace_id_map_default()))
+				      &sink->perf_id_map))
 		goto fail_disable_path;
 
 	/*
@@ -509,8 +511,7 @@ static void etm_event_start(struct perf_event *event, int flags)
 		hw_id = FIELD_PREP(CS_AUX_HW_ID_VERSION_MASK,
 				   CS_AUX_HW_ID_CURR_VERSION);
 		hw_id |= FIELD_PREP(CS_AUX_HW_ID_TRACE_ID_MASK,
-				    coresight_trace_id_read_cpu_id(cpu,
-						coresight_trace_id_map_default()));
+				    coresight_trace_id_read_cpu_id(cpu, &sink->perf_id_map));
 		perf_report_aux_output_id(event, hw_id);
 	}
 
diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index 3a678e5425dc..8c4c1860c76b 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -290,6 +290,7 @@ struct coresight_device {
 	bool sysfs_sink_activated;
 	struct dev_ext_attribute *ea;
 	struct coresight_device *def_sink;
+	struct coresight_trace_id_map perf_id_map;
 	/* sysfs links between components */
 	int nr_links;
 	bool has_conns_grp;
-- 
2.34.1