coresight-tpdm: Add reset node to TPDM node

TPDM device need a node to reset the configurations and status of
it. This change provides a node to reset the configurations and
disable the TPDM if it has been enabled.
Signed-off-by: Tao Zhang <quic_taozha@quicinc.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/1695882586-10306-7-git-send-email-quic_taozha@quicinc.com

Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm

@@ -11,3 +11,13 @@ Description:
 		Accepts only one of the 2 values -  1 or 2.
 		1 : Generate 64 bits data
 		2 : Generate 32 bits data
+
+What:		/sys/bus/coresight/devices/<tpdm-name>/reset_dataset
+Date:		March 2023
+KernelVersion	6.7
+Contact:	Jinlong Mao (QUIC) <quic_jinlmao@quicinc.com>, Tao Zhang (QUIC) <quic_taozha@quicinc.com>
+Description:
+		(Write) Reset the dataset of the tpdm.
+
+		Accepts only one value -  1.
+		1 : Reset the dataset of the tpdm

drivers/hwtracing/coresight/coresight-tpdm.c

@@ -162,6 +162,27 @@ static int tpdm_datasets_setup(struct tpdm_drvdata *drvdata)
 	return 0;
 }
 
+static ssize_t reset_dataset_store(struct device *dev,
+				   struct device_attribute *attr,
+				   const char *buf,
+				   size_t size)
+{
+	int ret = 0;
+	unsigned long val;
+	struct tpdm_drvdata *drvdata = dev_get_drvdata(dev->parent);
+
+	ret = kstrtoul(buf, 0, &val);
+	if (ret || val != 1)
+		return -EINVAL;
+
+	spin_lock(&drvdata->spinlock);
+	tpdm_reset_datasets(drvdata);
+	spin_unlock(&drvdata->spinlock);
+
+	return size;
+}
+static DEVICE_ATTR_WO(reset_dataset);
+
 /*
  * value 1: 64 bits test data
  * value 2: 32 bits test data
@@ -202,6 +223,7 @@ static ssize_t integration_test_store(struct device *dev,
 static DEVICE_ATTR_WO(integration_test);
 
 static struct attribute *tpdm_attrs[] = {
+	&dev_attr_reset_dataset.attr,
 	&dev_attr_integration_test.attr,
 	NULL,
 };