driver core: Set deferred probe reason when deferred by driver core

When the driver core defers the probe of a device, set the deferred
probe reason so that it's easier to debug. The deferred probe reason is
available in debugfs under devices_deferred.
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20210915172808.620546-2-saravanak@google.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/core.c

@@ -975,6 +975,7 @@ int device_links_check_suppliers(struct device *dev)
 {
 	struct device_link *link;
 	int ret = 0;
+	struct fwnode_handle *sup_fw;
 
 	/*
 	 * Device waiting for supplier to become available is not allowed to
@@ -983,10 +984,11 @@ int device_links_check_suppliers(struct device *dev)
 	mutex_lock(&fwnode_link_lock);
 	if (dev->fwnode && !list_empty(&dev->fwnode->suppliers) &&
 	    !fw_devlink_is_permissive()) {
-		dev_dbg(dev, "probe deferral - wait for supplier %pfwP\n",
-			list_first_entry(&dev->fwnode->suppliers,
+		sup_fw = list_first_entry(&dev->fwnode->suppliers,
 					  struct fwnode_link,
-			c_hook)->supplier);
+					  c_hook)->supplier;
+		dev_err_probe(dev, -EPROBE_DEFER, "wait for supplier %pfwP\n",
+			      sup_fw);
 		mutex_unlock(&fwnode_link_lock);
 		return -EPROBE_DEFER;
 	}
@@ -1001,7 +1003,8 @@ int device_links_check_suppliers(struct device *dev)
 		if (link->status != DL_STATE_AVAILABLE &&
 		    !(link->flags & DL_FLAG_SYNC_STATE_ONLY)) {
 			device_links_missing_supplier(dev);
-			dev_dbg(dev, "probe deferral - supplier %s not ready\n",
+			dev_err_probe(dev, -EPROBE_DEFER,
+				      "supplier %s not ready\n",
 				      dev_name(link->supplier));
 			ret = -EPROBE_DEFER;
 			break;