linux-kernel - [PATCH V3 08/14] coresight: core: Add support for dedicated percpu sinks

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Date:   Wed, 27 Jan 2021 14:25:32 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-arm-kernel@...ts.infradead.org, coresight@...ts.linaro.org
Cc:     mathieu.poirier@...aro.org, suzuki.poulose@....com,
        mike.leach@...aro.org, lcherian@...vell.com,
        linux-kernel@...r.kernel.org,
        Anshuman Khandual <anshuman.khandual@....com>
Subject: [PATCH V3 08/14] coresight: core: Add support for dedicated percpu sinks

Add support for dedicated sinks that are bound to individual CPUs. (e.g,
TRBE). To allow quicker access to the sink for a given CPU bound source,
keep a percpu array of the sink devices. Also, add support for building
a path to the CPU local sink from the ETM.

This adds a new percpu sink type CORESIGHT_DEV_SUBTYPE_SINK_PERCPU_SYSMEM.
This new sink type is exclusively available and can only work with percpu
source type device CORESIGHT_DEV_SUBTYPE_SOURCE_PERCPU_PROC.

This defines a percpu structure that accommodates a single coresight_device
which can be used to store an initialized instance from a sink driver. As
these sinks are exclusively linked and dependent on corresponding percpu
sources devices, they should also be the default sink device during a perf
session.

Outwards device connections are scanned while establishing paths between a
source and a sink device. But such connections are not present for certain
percpu source and sink devices which are exclusively linked and dependent.
Build the path directly and skip connection scanning for such devices.

Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
Cc: Mike Leach <mike.leach@...aro.org>
Cc: Suzuki K Poulose <suzuki.poulose@....com>
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
Changes in V3:

- Updated coresight_find_default_sink()

 drivers/hwtracing/coresight/coresight-core.c | 16 ++++++++++++++--
 include/linux/coresight.h                    | 12 ++++++++++++
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index 0062c89..4795e28 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -23,6 +23,7 @@
 #include "coresight-priv.h"
 
 static DEFINE_MUTEX(coresight_mutex);
+DEFINE_PER_CPU(struct coresight_device *, csdev_sink);
 
 /**
  * struct coresight_node - elements of a path, from source to sink
@@ -784,6 +785,13 @@ static int _coresight_build_path(struct coresight_device *csdev,
 	if (csdev == sink)
 		goto out;
 
+	if (coresight_is_percpu_source(csdev) && coresight_is_percpu_sink(sink) &&
+	    sink == per_cpu(csdev_sink, source_ops(csdev)->cpu_id(csdev))) {
+		_coresight_build_path(sink, sink, path);
+		found = true;
+		goto out;
+	}
+
 	/* Not a sink - recursively explore each port found on this element */
 	for (i = 0; i < csdev->pdata->nr_outport; i++) {
 		struct coresight_device *child_dev;
@@ -999,8 +1007,12 @@ coresight_find_default_sink(struct coresight_device *csdev)
 	int depth = 0;
 
 	/* look for a default sink if we have not found for this device */
-	if (!csdev->def_sink)
-		csdev->def_sink = coresight_find_sink(csdev, &depth);
+	if (!csdev->def_sink) {
+		if (coresight_is_percpu_source(csdev))
+			csdev->def_sink = per_cpu(csdev_sink, source_ops(csdev)->cpu_id(csdev));
+		if (!csdev->def_sink)
+			csdev->def_sink = coresight_find_sink(csdev, &depth);
+	}
 	return csdev->def_sink;
 }
 
diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index 976ec26..bc3a5ca 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -50,6 +50,7 @@ enum coresight_dev_subtype_sink {
 	CORESIGHT_DEV_SUBTYPE_SINK_PORT,
 	CORESIGHT_DEV_SUBTYPE_SINK_BUFFER,
 	CORESIGHT_DEV_SUBTYPE_SINK_SYSMEM,
+	CORESIGHT_DEV_SUBTYPE_SINK_PERCPU_SYSMEM,
 };
 
 enum coresight_dev_subtype_link {
@@ -428,6 +429,17 @@ static inline void csdev_access_write64(struct csdev_access *csa, u64 val, u32 o
 		csa->write(val, offset, false, true);
 }
 
+static inline bool coresight_is_percpu_source(struct coresight_device *csdev)
+{
+	return csdev && (csdev->type == CORESIGHT_DEV_TYPE_SOURCE) &&
+	       csdev->subtype.source_subtype == CORESIGHT_DEV_SUBTYPE_SOURCE_PROC;
+}
+
+static inline bool coresight_is_percpu_sink(struct coresight_device *csdev)
+{
+	return csdev && (csdev->type == CORESIGHT_DEV_TYPE_SINK) &&
+	       csdev->subtype.sink_subtype == CORESIGHT_DEV_SUBTYPE_SINK_PERCPU_SYSMEM;
+}
 #else	/* !CONFIG_64BIT */
 
 static inline u64 csdev_access_relaxed_read64(struct csdev_access *csa,
-- 
2.7.4