coresight: Fix CTI module refcount leak by making it a helper device

The CTI module has some hard coded refcounting code that has a leak.
For example running perf and then trying to unload it fails:

  perf record -e cs_etm// -a -- ls
  rmmod coresight_cti

  rmmod: ERROR: Module coresight_cti is in use

The coresight core already handles references of devices in use, so by
making CTI a normal helper device, we get working refcounting for free.

Reviewed-by: Mike Leach  <mike.leach@linaro.org>
Signed-off-by: James Clark <james.clark@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20230425143542.2305069-14-james.clark@arm.com

1 files changed, 28 insertions, 24 deletions

diff --git a/drivers/hwtracing/coresight/coresight-cti-core.c b/drivers/hwtracing/coresight/coresight-cti-core.c
index 277c890a1f1f..7023ff70cc28 100644
--- a/drivers/hwtracing/coresight/coresight-cti-core.c
+++ b/drivers/hwtracing/coresight/coresight-cti-core.c
@@ -555,7 +555,10 @@ static void cti_add_assoc_to_csdev(struct coresight_device *csdev)
 	mutex_lock(&ect_mutex);
 
 	/* exit if current is an ECT device.*/
-	if ((csdev->type == CORESIGHT_DEV_TYPE_ECT) || list_empty(&ect_net))
+	if ((csdev->type == CORESIGHT_DEV_TYPE_HELPER &&
+	     csdev->subtype.helper_subtype ==
+		     CORESIGHT_DEV_SUBTYPE_HELPER_ECT_CTI) ||
+	    list_empty(&ect_net))
 		goto cti_add_done;
 
 	/* if we didn't find the csdev previously we used the fwnode name */
@@ -571,8 +574,7 @@ static void cti_add_assoc_to_csdev(struct coresight_device *csdev)
 			 * if we found a matching csdev then update the ECT
 			 * association pointer for the device with this CTI.
 			 */
-			coresight_set_assoc_ectdev_mutex(csdev,
-							 ect_item->csdev);
+			coresight_add_helper(csdev, ect_item->csdev);
 			break;
 		}
 	}
@@ -582,26 +584,30 @@ cti_add_done:
 
 /*
  * Removing the associated devices is easier.
- * A CTI will not have a value for csdev->ect_dev.
  */
 static void cti_remove_assoc_from_csdev(struct coresight_device *csdev)
 {
 	struct cti_drvdata *ctidrv;
 	struct cti_trig_con *tc;
 	struct cti_device *ctidev;
+	union coresight_dev_subtype cti_subtype = {
+		.helper_subtype = CORESIGHT_DEV_SUBTYPE_HELPER_ECT_CTI
+	};
+	struct coresight_device *cti_csdev = coresight_find_output_type(
+		csdev->pdata, CORESIGHT_DEV_TYPE_HELPER, cti_subtype);
+
+	if (!cti_csdev)
+		return;
 
 	mutex_lock(&ect_mutex);
-	if (csdev->ect_dev) {
-		ctidrv = csdev_to_cti_drvdata(csdev->ect_dev);
-		ctidev = &ctidrv->ctidev;
-		list_for_each_entry(tc, &ctidev->trig_cons, node) {
-			if (tc->con_dev == csdev) {
-				cti_remove_sysfs_link(ctidrv, tc);
-				tc->con_dev = NULL;
-				break;
-			}
+	ctidrv = csdev_to_cti_drvdata(cti_csdev);
+	ctidev = &ctidrv->ctidev;
+	list_for_each_entry(tc, &ctidev->trig_cons, node) {
+		if (tc->con_dev == csdev) {
+			cti_remove_sysfs_link(ctidrv, tc);
+			tc->con_dev = NULL;
+			break;
 		}
-		csdev->ect_dev = NULL;
 	}
 	mutex_unlock(&ect_mutex);
 }
@@ -630,8 +636,8 @@ static void cti_update_conn_xrefs(struct cti_drvdata *drvdata)
 			/* 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);
+				coresight_add_helper(tc->con_dev,
+						     drvdata->csdev);
 			else
 				/* otherwise remove reference from CTI */
 				tc->con_dev = NULL;
@@ -646,8 +652,6 @@ static void cti_remove_conn_xrefs(struct cti_drvdata *drvdata)
 
 	list_for_each_entry(tc, &ctidev->trig_cons, node) {
 		if (tc->con_dev) {
-			coresight_set_assoc_ectdev_mutex(tc->con_dev,
-							 NULL);
 			cti_remove_sysfs_link(drvdata, tc);
 			tc->con_dev = NULL;
 		}
@@ -795,27 +799,27 @@ static void cti_pm_release(struct cti_drvdata *drvdata)
 }
 
 /** cti ect operations **/
-int cti_enable(struct coresight_device *csdev)
+int cti_enable(struct coresight_device *csdev, enum cs_mode mode, void *data)
 {
 	struct cti_drvdata *drvdata = csdev_to_cti_drvdata(csdev);
 
 	return cti_enable_hw(drvdata);
 }
 
-int cti_disable(struct coresight_device *csdev)
+int cti_disable(struct coresight_device *csdev, void *data)
 {
 	struct cti_drvdata *drvdata = csdev_to_cti_drvdata(csdev);
 
 	return cti_disable_hw(drvdata);
 }
 
-static const struct coresight_ops_ect cti_ops_ect = {
+static const struct coresight_ops_helper cti_ops_ect = {
 	.enable = cti_enable,
 	.disable = cti_disable,
 };
 
 static const struct coresight_ops cti_ops = {
-	.ect_ops = &cti_ops_ect,
+	.helper_ops = &cti_ops_ect,
 };
 
 /*
@@ -922,8 +926,8 @@ static int cti_probe(struct amba_device *adev, const struct amba_id *id)
 
 	/* set up coresight component description */
 	cti_desc.pdata = pdata;
-	cti_desc.type = CORESIGHT_DEV_TYPE_ECT;
-	cti_desc.subtype.ect_subtype = CORESIGHT_DEV_SUBTYPE_ECT_CTI;
+	cti_desc.type = CORESIGHT_DEV_TYPE_HELPER;
+	cti_desc.subtype.helper_subtype = CORESIGHT_DEV_SUBTYPE_HELPER_ECT_CTI;
 	cti_desc.ops = &cti_ops;
 	cti_desc.groups = drvdata->ctidev.con_groups;
 	cti_desc.dev = dev;