linux-kernel - [PATCH v1 1/5] driver core: Add debug logs for device link related probe deferrals

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Date:   Thu, 17 Dec 2020 19:16:59 -0800
From:   Saravana Kannan <saravanak@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Saravana Kannan <saravanak@...gle.com>, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org,
        Jisheng Zhang <Jisheng.Zhang@...aptics.com>,
        Kevin Hilman <khilman@...libre.com>,
        John Stultz <john.stultz@...aro.org>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Marc Zyngier <maz@...nel.org>
Subject: [PATCH v1 1/5] driver core: Add debug logs for device link related
 probe deferrals

There's insufficient logging when device links or fw_devlink (waiting to
create device links) cause probe deferrals.  This makes it hard to debug
devices not getting probed. So, add debug logs to make it easy to debug.

Signed-off-by: Saravana Kannan <saravanak@...gle.com>
---
 drivers/base/core.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 25e08e5f40bd..fe8601197b84 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -929,6 +929,10 @@ 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,
+			struct fwnode_link,
+			c_hook)->supplier);
 		mutex_unlock(&fwnode_link_lock);
 		return -EPROBE_DEFER;
 	}
@@ -943,6 +947,8 @@ 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_name(link->supplier));
 			ret = -EPROBE_DEFER;
 			break;
 		}
-- 
2.29.2.684.gfbc64c5ab5-goog