coresight: cti: Add in sysfs links to other coresight devices

Adds in sysfs links for connections where the connected device is another
coresight device. This allows examination of the coresight topology.

Non-coresight connections remain just as a reference name.

Signed-off-by: Mike Leach <mike.leach@linaro.org>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20200518180242.7916-6-mathieu.poirier@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/coresight/coresight-cti.c

@@ -442,6 +442,34 @@ int cti_channel_setop(struct device *dev, enum cti_chan_set_op op,
 	return err;
 }
 
+static bool cti_add_sysfs_link(struct cti_drvdata *drvdata,
+			       struct cti_trig_con *tc)
+{
+	struct coresight_sysfs_link link_info;
+	int link_err = 0;
+
+	link_info.orig = drvdata->csdev;
+	link_info.orig_name = tc->con_dev_name;
+	link_info.target = tc->con_dev;
+	link_info.target_name = dev_name(&drvdata->csdev->dev);
+
+	link_err = coresight_add_sysfs_link(&link_info);
+	if (link_err)
+		dev_warn(&drvdata->csdev->dev,
+			 "Failed to set CTI sysfs link %s<=>%s\n",
+			 link_info.orig_name, link_info.target_name);
+	return !link_err;
+}
+
+static void cti_remove_sysfs_link(struct cti_trig_con *tc)
+{
+	struct coresight_sysfs_link link_info;
+
+	link_info.orig_name = tc->con_dev_name;
+	link_info.target = tc->con_dev;
+	coresight_remove_sysfs_link(&link_info);
+}
+
 /*
  * Look for a matching connection device name in the list of connections.
  * If found then swap in the csdev name, set trig con association pointer
@@ -452,14 +480,21 @@ cti_match_fixup_csdev(struct cti_device *ctidev, const char *node_name,
 		      struct coresight_device *csdev)
 {
 	struct cti_trig_con *tc;
+	struct cti_drvdata *drvdata = container_of(ctidev, struct cti_drvdata,
+						   ctidev);
 
 	list_for_each_entry(tc, &ctidev->trig_cons, node) {
 		if (tc->con_dev_name) {
 			if (!strcmp(node_name, tc->con_dev_name)) {
 				/* match: so swap in csdev name & dev */
 				tc->con_dev_name = dev_name(&csdev->dev);
 				tc->con_dev = csdev;
-				return true;
+				/* try to set sysfs link */
+				if (cti_add_sysfs_link(drvdata, tc))
+					return true;
+				/* link failed - remove CTI reference */
+				tc->con_dev = NULL;
+				break;
 			}
 		}
 	}
@@ -522,6 +557,7 @@ void cti_remove_assoc_from_csdev(struct coresight_device *csdev)
 		ctidev = &ctidrv->ctidev;
 		list_for_each_entry(tc, &ctidev->trig_cons, node) {
 			if (tc->con_dev == csdev->ect_dev) {
+				cti_remove_sysfs_link(tc);
 				tc->con_dev = NULL;
 				break;
 			}
@@ -543,10 +579,16 @@ static void cti_update_conn_xrefs(struct cti_drvdata *drvdata)
 	struct cti_device *ctidev = &drvdata->ctidev;
 
 	list_for_each_entry(tc, &ctidev->trig_cons, node) {
-		if (tc->con_dev)
-			/* set tc->con_dev->ect_dev */
-			coresight_set_assoc_ectdev_mutex(tc->con_dev,
+		if (tc->con_dev) {
+			/* if we can set the sysfs link */
+			if (cti_add_sysfs_link(drvdata, tc))
+				/* set the CTI/csdev association */
+				coresight_set_assoc_ectdev_mutex(tc->con_dev,
 							 drvdata->csdev);
+			else
+				/* otherwise remove reference from CTI */
+				tc->con_dev = NULL;
+		}
 	}
 }
 
@@ -559,6 +601,8 @@ static void cti_remove_conn_xrefs(struct cti_drvdata *drvdata)
 		if (tc->con_dev) {
 			coresight_set_assoc_ectdev_mutex(tc->con_dev,
 							 NULL);
+			cti_remove_sysfs_link(tc);
+			tc->con_dev = NULL;
 		}
 	}
 }