[PATCH v4 05/15] coresight: Add callback to determine if PM is needed

[Leo Yan]

Add a callback in the source device that returns a boolean indicating
whether power management operations are required. The save and restore
flow is skipped if the callback returns false.

The ETMv4 driver implements its own version's callback.

Signed-off-by: Leo Yan <leo.yan at arm.com>
---
 drivers/hwtracing/coresight/coresight-core.c       |  9 ++++++++-
 drivers/hwtracing/coresight/coresight-etm4x-core.c | 16 ++++++++++++++++
 include/linux/coresight.h                          |  1 +
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index f642190740b93555084584abbc1d9426cc87ec7c..0d4e935094297023b8a7786ff4b1b3783164016b 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -1586,7 +1586,14 @@ static bool coresight_pm_is_needed(struct coresight_device *csdev)
 	    !coresight_ops(csdev)->pm_restore_enable)
 		return false;
 
-	return true;
+	/*
+	 * PM callbacks are provided but pm_is_neended() is absent, it means
+	 * no extra check is needed.
+	 */
+	if (!coresight_ops(csdev)->pm_is_needed)
+		return true;
+
+	return coresight_ops(csdev)->pm_is_needed(csdev);
 }
 
 static int coresight_pm_save(struct coresight_device *csdev)
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index adb5c6b12c6f3113747f1f455087b1ab497a53f6..da135849c70833366aa1089a0752bc7844c0d96d 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -1838,6 +1838,21 @@ static int etm4_dying_cpu(unsigned int cpu)
 	return 0;
 }
 
+static bool etm4_need_save_restore_context(struct coresight_device *csdev)
+{
+	if (pm_save_enable != PARAM_PM_SAVE_SELF_HOSTED)
+		return false;
+
+	/*
+	 * Save and restore the ETM Trace registers only if
+	 * the ETM is active.
+	 */
+	if (coresight_get_mode(csdev))
+		return true;
+
+	return false;
+}
+
 static int __etm4_cpu_save(struct etmv4_drvdata *drvdata)
 {
 	int ret = 0;
@@ -1929,6 +1944,7 @@ static const struct coresight_ops etm4_cs_ops = {
 	.trace_id		= coresight_etm_get_trace_id,
 	.pm_save_disable	= etm4_cpu_save,
 	.pm_restore_enable	= etm4_cpu_restore,
+	.pm_is_needed		= etm4_need_save_restore_context,
 	.source_ops		= &etm4_source_ops,
 };
 
diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index b10ef4fa17a76b4d11223cc8fd43e5544b6ea8b9..3d59be214dd25dfa7ad9148a6688628e0d1a98dd 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -441,6 +441,7 @@ struct coresight_ops {
 			struct coresight_device *sink);
 	int (*pm_save_disable)(struct coresight_device *csdev);
 	void (*pm_restore_enable)(struct coresight_device *csdev);
+	bool (*pm_is_needed)(struct coresight_device *csdev);
 	const struct coresight_ops_sink *sink_ops;
 	const struct coresight_ops_link *link_ops;
 	const struct coresight_ops_source *source_ops;

-- 
2.34.1