linux-kernel - [PATCH] driver core: Don't try to create links if they are not needed

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Message-ID: <20240910130019.35081-1-jonathanh@nvidia.com>
Date: Tue, 10 Sep 2024 14:00:19 +0100
From: Jon Hunter <jonathanh@...dia.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J . Wysocki"
	<rafael@...nel.org>, Saravana Kannan <saravanak@...gle.com>
CC: <linux-kernel@...r.kernel.org>, <linux-tegra@...r.kernel.org>, Jon Hunter
	<jonathanh@...dia.com>
Subject: [PATCH] driver core: Don't try to create links if they are not needed

The following error messages are observed on boot with the Tegra234
Jetson AGX Orin board ...

 tegra-xusb-padctl 3520000.padctl: Failed to create device link (0x180)
   with 1-0008
 tegra-xusb-padctl 3520000.padctl: Failed to create device link (0x180)
   with 1-0008
 tegra-xusb-padctl 3520000.padctl: Failed to create device link (0x180)
   with 1-0008

In the above case, device_link_add() intentionally returns NULL because
these are SYNC_STATE_ONLY links and the device is already probed.
Therefore, the above messages are not actually errors. Fix this by
replicating the test from device_link_add() in the function
fw_devlink_create_devlink() and don't call device_link_add() if there
are no links to create.

Signed-off-by: Jon Hunter <jonathanh@...dia.com>
---
I am not sure if there is a better way to fix, but given that the
function device_link_add() is exported, I figured we could not just
move the test. Anyway, if there is a better way to fix this, let me
know.

 drivers/base/core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index b69b82da8837..5d6575e63e8b 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2181,6 +2181,15 @@ static int fw_devlink_create_devlink(struct device *con,
 			goto out;
 		}
 
+		/*
+		 * SYNC_STATE_ONLY links are useless once a consumer device has probed.
+		 * So, only create it if the consumer hasn't probed yet.
+		 */
+		if (flags & DL_FLAG_SYNC_STATE_ONLY &&
+		    con->links.status != DL_DEV_NO_DRIVER &&
+		    con->links.status != DL_DEV_PROBING)
+			goto out;
+
 		if (con != sup_dev && !device_link_add(con, sup_dev, flags)) {
 			dev_err(con, "Failed to create device link (0x%x) with %s\n",
 				flags, dev_name(sup_dev));
-- 
2.34.1