media: v4l: async: Add some debug prints

Just add some debug prints for V4L2 async sub-device matching process.
These might come useful in figuring out why things don't work as expected.
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Tested-by: Philipp Zabel <p.zabel@pengutronix.de> # imx6qp
Tested-by: Niklas Söderlund <niklas.soderlund@ragnatech.se> # rcar + adv746x
Tested-by: Aishwarya Kothari <aishwarya.kothari@toradex.com> # Apalis i.MX6Q with TC358743
Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com> # Renesas RZ/G2L SMARC
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/v4l2-core/v4l2-async.c

@@ -77,6 +77,17 @@ static bool match_i2c(struct v4l2_async_notifier *notifier,
 #endif
 }
 
+static struct device *notifier_dev(struct v4l2_async_notifier *notifier)
+{
+	if (notifier->sd)
+		return notifier->sd->dev;
+
+	if (notifier->v4l2_dev)
+		return notifier->v4l2_dev->dev;
+
+	return NULL;
+}
+
 static bool
 match_fwnode_one(struct v4l2_async_notifier *notifier,
 		 struct v4l2_subdev *sd, struct fwnode_handle *sd_fwnode,
@@ -88,13 +99,20 @@ match_fwnode_one(struct v4l2_async_notifier *notifier,
 	bool sd_fwnode_is_ep;
 	struct device *dev;
 
+	dev_dbg(notifier_dev(notifier),
+		"v4l2-async: fwnode match: need %pfw, trying %pfw\n",
+		sd_fwnode, asd->match.fwnode);
+
 	/*
 	 * Both the subdev and the async subdev can provide either an endpoint
 	 * fwnode or a device fwnode. Start with the simple case of direct
 	 * fwnode matching.
 	 */
-	if (sd_fwnode == asd->match.fwnode)
+	if (sd_fwnode == asd->match.fwnode) {
+		dev_dbg(notifier_dev(notifier),
+			"v4l2-async: direct match found\n");
 		return true;
+	}
 
 	/*
 	 * Otherwise, check if the sd fwnode and the asd fwnode refer to an
@@ -107,8 +125,11 @@ match_fwnode_one(struct v4l2_async_notifier *notifier,
 	sd_fwnode_is_ep = fwnode_graph_is_endpoint(sd_fwnode);
 	asd_fwnode_is_ep = fwnode_graph_is_endpoint(asd->match.fwnode);
 
-	if (sd_fwnode_is_ep == asd_fwnode_is_ep)
+	if (sd_fwnode_is_ep == asd_fwnode_is_ep) {
+		dev_dbg(notifier_dev(notifier),
+			"v4l2-async: direct match not found\n");
 		return false;
+	}
 
 	/*
 	 * The sd and asd fwnodes are of different types. Get the device fwnode
@@ -122,10 +143,17 @@ match_fwnode_one(struct v4l2_async_notifier *notifier,
 		other_fwnode = sd_fwnode;
 	}
 
+	dev_dbg(notifier_dev(notifier),
+		"v4l2-async: fwnode compat match: need %pfw, trying %pfw\n",
+		dev_fwnode, other_fwnode);
+
 	fwnode_handle_put(dev_fwnode);
 
-	if (dev_fwnode != other_fwnode)
+	if (dev_fwnode != other_fwnode) {
+		dev_dbg(notifier_dev(notifier),
+			"v4l2-async: compat match not found\n");
 		return false;
+	}
 
 	/*
 	 * We have a heterogeneous match. Retrieve the struct device of the side
@@ -145,12 +173,18 @@ match_fwnode_one(struct v4l2_async_notifier *notifier,
 			   dev->driver->name);
 	}
 
+	dev_dbg(notifier_dev(notifier), "v4l2-async: compat match found\n");
+
 	return true;
 }
 
 static bool match_fwnode(struct v4l2_async_notifier *notifier,
 			 struct v4l2_subdev *sd, struct v4l2_async_subdev *asd)
 {
+	dev_dbg(notifier_dev(notifier),
+		"v4l2-async: matching for notifier %pfw, sd fwnode %pfw\n",
+		dev_fwnode(notifier_dev(notifier)), sd->fwnode);
+
 	if (match_fwnode_one(notifier, sd, sd->fwnode, asd))
 		return true;
 
@@ -158,6 +192,9 @@ static bool match_fwnode(struct v4l2_async_notifier *notifier,
 	if (IS_ERR_OR_NULL(sd->fwnode->secondary))
 		return false;
 
+	dev_dbg(notifier_dev(notifier),
+		"v4l2-async: trying secondary fwnode match\n");
+
 	return match_fwnode_one(notifier, sd, sd->fwnode->secondary, asd);
 }
 
@@ -271,22 +308,33 @@ v4l2_async_nf_can_complete(struct v4l2_async_notifier *notifier)
 static int
 v4l2_async_nf_try_complete(struct v4l2_async_notifier *notifier)
 {
+	struct v4l2_async_notifier *__notifier = notifier;
+
 	/* Quick check whether there are still more sub-devices here. */
 	if (!list_empty(&notifier->waiting))
 		return 0;
 
+	if (notifier->sd)
+		dev_dbg(notifier_dev(notifier),
+			"v4l2-async: trying to complete\n");
+
 	/* Check the entire notifier tree; find the root notifier first. */
 	while (notifier->parent)
 		notifier = notifier->parent;
 
 	/* This is root if it has v4l2_dev. */
-	if (!notifier->v4l2_dev)
+	if (!notifier->v4l2_dev) {
+		dev_dbg(notifier_dev(__notifier),
+			"v4l2-async: V4L2 device not available\n");
 		return 0;
+	}
 
 	/* Is everything ready? */
 	if (!v4l2_async_nf_can_complete(notifier))
 		return 0;
 
+	dev_dbg(notifier_dev(__notifier), "v4l2-async: complete\n");
+
 	return v4l2_async_nf_call_complete(notifier);
 }
 
@@ -350,6 +398,9 @@ static int v4l2_async_match_notify(struct v4l2_async_notifier *notifier,
 	/* Move from the global subdevice list to notifier's done */
 	list_move(&sd->async_list, &notifier->done);
 
+	dev_dbg(notifier_dev(notifier), "v4l2-async: %s bound (ret %d)\n",
+		dev_name(sd->dev), ret);
+
 	/*
 	 * See if the sub-device has a notifier. If not, return here.
 	 */
@@ -378,6 +429,8 @@ v4l2_async_nf_try_all_subdevs(struct v4l2_async_notifier *notifier)
 	if (!v4l2_dev)
 		return 0;
 
+	dev_dbg(notifier_dev(notifier), "v4l2-async: trying all sub-devices\n");
+
 again:
 	list_for_each_entry(sd, &subdev_list, async_list) {
 		struct v4l2_async_subdev *asd;
@@ -387,6 +440,9 @@ v4l2_async_nf_try_all_subdevs(struct v4l2_async_notifier *notifier)
 		if (!asd)
 			continue;
 
+		dev_dbg(notifier_dev(notifier),
+			"v4l2-async: match found, subdev %s\n", sd->name);
+
 		ret = v4l2_async_match_notify(notifier, v4l2_dev, sd, asd);
 		if (ret < 0)
 			return ret;
@@ -496,8 +552,7 @@ static int v4l2_async_nf_asd_valid(struct v4l2_async_notifier *notifier,
 				   struct v4l2_async_subdev *asd,
 				   int this_index)
 {
-	struct device *dev =
-		notifier->v4l2_dev ? notifier->v4l2_dev->dev : NULL;
+	struct device *dev = notifier_dev(notifier);
 
 	if (!asd)
 		return -EINVAL;
@@ -506,12 +561,12 @@ static int v4l2_async_nf_asd_valid(struct v4l2_async_notifier *notifier,
 	case V4L2_ASYNC_MATCH_I2C:
 	case V4L2_ASYNC_MATCH_FWNODE:
 		if (v4l2_async_nf_has_async_subdev(notifier, asd, this_index)) {
-			dev_dbg(dev, "subdev descriptor already listed in this or other notifiers\n");
+			dev_dbg(dev, "v4l2-async: subdev descriptor already listed in a notifier\n");
 			return -EEXIST;
 		}
 		break;
 	default:
-		dev_err(dev, "Invalid match type %u on %p\n",
+		dev_err(dev, "v4l2-async: Invalid match type %u on %p\n",
 			asd->match_type, asd);
 		return -EINVAL;
 	}