coresight: etm4x: Hook pause and resume callbacks

Add callbacks for pausing and resuming the tracer.

A "paused" flag in the driver data indicates whether the tracer is
paused.  If the flag is set, the driver will skip starting the hardware
trace.  The flag is always set to false for the sysfs mode, meaning the
tracer will never be paused in the case.

Signed-off-by: Leo Yan <leo.yan@arm.com>
Reviewed-by: Mike Leach <mike.leach@linaro.org>
Reviewed-by: James Clark <james.clark@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20250401180708.385396-4-leo.yan@arm.com

Author: Leo-Yan

drivers/hwtracing/coresight/coresight-etm4x-core.c

@@ -577,7 +577,8 @@ static int etm4_enable_hw(struct etmv4_drvdata *drvdata)
 		etm4x_relaxed_write32(csa, trcpdcr | TRCPDCR_PU, TRCPDCR);
 	}
 
-	rc = etm4_enable_trace_unit(drvdata);
+	if (!drvdata->paused)
+		rc = etm4_enable_trace_unit(drvdata);
 done:
 	etm4_cs_lock(drvdata, csa);
 
@@ -820,6 +821,9 @@ static int etm4_enable_perf(struct coresight_device *csdev,
 
 	drvdata->trcid = path->trace_id;
 
+	/* Populate pause state */
+	drvdata->paused = !!READ_ONCE(event->hw.aux_paused);
+
 	/* And enable it */
 	ret = etm4_enable_hw(drvdata);
 
@@ -846,6 +850,9 @@ static int etm4_enable_sysfs(struct coresight_device *csdev, struct coresight_pa
 
 	drvdata->trcid = path->trace_id;
 
+	/* Tracer will never be paused in sysfs mode */
+	drvdata->paused = false;
+
 	/*
 	 * Executing etm4_enable_hw on the cpu whose ETM is being enabled
 	 * ensures that register writes occur when cpu is powered.
@@ -1080,10 +1087,43 @@ static void etm4_disable(struct coresight_device *csdev,
 		coresight_set_mode(csdev, CS_MODE_DISABLED);
 }
 
+static int etm4_resume_perf(struct coresight_device *csdev)
+{
+	struct etmv4_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
+	struct csdev_access *csa = &csdev->access;
+
+	if (coresight_get_mode(csdev) != CS_MODE_PERF)
+		return -EINVAL;
+
+	etm4_cs_unlock(drvdata, csa);
+	etm4_enable_trace_unit(drvdata);
+	etm4_cs_lock(drvdata, csa);
+
+	drvdata->paused = false;
+	return 0;
+}
+
+static void etm4_pause_perf(struct coresight_device *csdev)
+{
+	struct etmv4_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
+	struct csdev_access *csa = &csdev->access;
+
+	if (coresight_get_mode(csdev) != CS_MODE_PERF)
+		return;
+
+	etm4_cs_unlock(drvdata, csa);
+	etm4_disable_trace_unit(drvdata);
+	etm4_cs_lock(drvdata, csa);
+
+	drvdata->paused = true;
+}
+
 static const struct coresight_ops_source etm4_source_ops = {
 	.cpu_id		= etm4_cpu_id,
 	.enable		= etm4_enable,
 	.disable	= etm4_disable,
+	.resume_perf	= etm4_resume_perf,
+	.pause_perf	= etm4_pause_perf,
 };
 
 static const struct coresight_ops etm4_cs_ops = {

drivers/hwtracing/coresight/coresight-etm4x.h

@@ -983,6 +983,7 @@ struct etmv4_save_state {
  * @state_needs_restore: True when there is context to restore after PM exit
  * @skip_power_up: Indicates if an implementation can skip powering up
  *		   the trace unit.
+ * @paused:	Indicates if the trace unit is paused.
  * @arch_features: Bitmap of arch features of etmv4 devices.
  */
 struct etmv4_drvdata {
@@ -1036,6 +1037,7 @@ struct etmv4_drvdata {
 	struct etmv4_save_state		*save_state;
 	bool				state_needs_restore;
 	bool				skip_power_up;
+	bool				paused;
 	DECLARE_BITMAP(arch_features, ETM4_IMPDEF_FEATURE_MAX);
 };