coresight: core: Fix coresight device probe failure issue

It is possibe that probe failure issue happens when the device
and its child_device's probe happens at the same time.
In coresight_make_links, has_conns_grp is true for parent, but
has_conns_grp is false for child device as has_conns_grp is set
to true in coresight_create_conns_sysfs_group. The probe of parent
device will fail at this condition. Add has_conns_grp check for
child device before make the links and make the process from
device_register to connection_create be atomic to avoid this
probe failure issue.

Cc: stable@vger.kernel.org
Suggested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Suggested-by: Mike Leach <mike.leach@linaro.org>
Signed-off-by: Mao Jinlong <quic_jinlmao@quicinc.com>
Link: https://lore.kernel.org/r/20220309142206.15632-1-quic_jinlmao@quicinc.com
[ Added Cc stable ]
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index af00dca..ee6ce92 100644 (file)
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -1379,7 +1379,7 @@ static int coresight_fixup_device_conns(struct coresight_device *csdev)
                        continue;
                conn->child_dev =
                        coresight_find_csdev_by_fwnode(conn->child_fwnode);
-               if (conn->child_dev) {
+               if (conn->child_dev && conn->child_dev->has_conns_grp) {
                        ret = coresight_make_links(csdev, conn,
                                                   conn->child_dev);
                        if (ret)
@@ -1571,6 +1571,7 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
        int nr_refcnts = 1;
        atomic_t *refcnts = NULL;
        struct coresight_device *csdev;
+       bool registered = false;
 
        csdev = kzalloc(sizeof(*csdev), GFP_KERNEL);
        if (!csdev) {
@@ -1591,7 +1592,8 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
        refcnts = kcalloc(nr_refcnts, sizeof(*refcnts), GFP_KERNEL);
        if (!refcnts) {
                ret = -ENOMEM;
-               goto err_free_csdev;
+               kfree(csdev);
+               goto err_out;
        }
 
        csdev->refcnt = refcnts;
@@ -1616,6 +1618,13 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
        csdev->dev.fwnode = fwnode_handle_get(dev_fwnode(desc->dev));
        dev_set_name(&csdev->dev, "%s", desc->name);
 
+       /*
+        * Make sure the device registration and the connection fixup
+        * are synchronised, so that we don't see uninitialised devices
+        * on the coresight bus while trying to resolve the connections.
+        */
+       mutex_lock(&coresight_mutex);
+
        ret = device_register(&csdev->dev);
        if (ret) {
                put_device(&csdev->dev);
@@ -1623,7 +1632,7 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
                 * All resources are free'd explicitly via
                 * coresight_device_release(), triggered from put_device().
                 */
-               goto err_out;
+               goto out_unlock;
        }
 
        if (csdev->type == CORESIGHT_DEV_TYPE_SINK ||
@@ -1638,11 +1647,11 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
                         * from put_device(), which is in turn called from
                         * function device_unregister().
                         */
-                       goto err_out;
+                       goto out_unlock;
                }
        }
-
-       mutex_lock(&coresight_mutex);
+       /* Device is now registered */
+       registered = true;
 
        ret = coresight_create_conns_sysfs_group(csdev);
        if (!ret)
@@ -1652,16 +1661,18 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
        if (!ret && cti_assoc_ops && cti_assoc_ops->add)
                cti_assoc_ops->add(csdev);
 
+out_unlock:
        mutex_unlock(&coresight_mutex);
-       if (ret) {
+       /* Success */
+       if (!ret)
+               return csdev;
+
+       /* Unregister the device if needed */
+       if (registered) {
                coresight_unregister(csdev);
                return ERR_PTR(ret);
        }
 
-       return csdev;
-
-err_free_csdev:
-       kfree(csdev);
 err_out:
        /* Cleanup the connection information */
        coresight_release_platform_data(NULL, desc->pdata);