coresight: Handle errors in finding input/output ports

If we fail to find the input / output port for a LINK component
while enabling a path, we should fail gracefully rather than
assuming port "0".

Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/coresight/coresight.c

@@ -107,7 +107,7 @@ static int coresight_find_link_inport(struct coresight_device *csdev,
 	dev_err(&csdev->dev, "couldn't find inport, parent: %s, child: %s\n",
 		dev_name(&parent->dev), dev_name(&csdev->dev));
 
-	return 0;
+	return -ENODEV;
 }
 
 static int coresight_find_link_outport(struct coresight_device *csdev,
@@ -125,7 +125,7 @@ static int coresight_find_link_outport(struct coresight_device *csdev,
 	dev_err(&csdev->dev, "couldn't find outport, parent: %s, child: %s\n",
 		dev_name(&csdev->dev), dev_name(&child->dev));
 
-	return 0;
+	return -ENODEV;
 }
 
 static int coresight_enable_sink(struct coresight_device *csdev, u32 mode)
@@ -178,6 +178,9 @@ static int coresight_enable_link(struct coresight_device *csdev,
 	else
 		refport = 0;
 
+	if (refport < 0)
+		return refport;
+
 	if (atomic_inc_return(&csdev->refcnt[refport]) == 1) {
 		if (link_ops(csdev)->enable) {
 			ret = link_ops(csdev)->enable(csdev, inport, outport);