netdev - [PATCH RFC] net/phy: fix Marvell PHYs probe failure when HWMON and THERMAL

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Date:   Thu, 19 Sep 2019 00:38:37 +0300
From:   Peter Mamonov <pmamonov@...il.com>
To:     andrew@...n.ch, f.fainelli@...il.com, hkallweit1@...il.com
Cc:     netdev@...r.kernel.org, Peter Mamonov <pmamonov@...il.com>
Subject: [PATCH RFC] net/phy: fix Marvell PHYs probe failure when HWMON and THERMAL_OF are enabled

Hello,

Some time ago I've discovered that probe functions of certain Marvell PHYs 
fail if both HWMON and THERMAL_OF config options are enabled. The root 
cause of this problem is a lack of an OF node for a PHY's built-in 
temperature sensor.  However I consider adding this OF node to be a bit 
excessive solution. Am I wrong? Below you will find a one line patch which 
fixes the problem. I've sent it to the releveant maintainers three weeks 
ago without any feedback yet. Could you, please, take a look at the problem 
and give your considerations on how to fix it properly?

Regards,
Peter

thermal: make thermal_zone_of_sensor_register return -ENODEV
 if a sensor OF node is missing

When devm_thermal_zone_of_sensor_register() is called from
hwmon_thermal_add_sensor() it is possible that the relevant sensor is
missing an OF node. In this case thermal_zone_of_sensor_register() returns
-EINVAL which causes hwmon_thermal_add_sensor() to fail as well. This patch
changes relevant return code of thermal_zone_of_sensor_register() to
-ENODEV, which is tolerated by hwmon_thermal_add_sensor().

Here is a particular case of such behaviour: the Marvell ethernet PHYs
driver registers hwmon device for the built-in temperature sensor (see
drivers/net/phy/marvell.c). Since the sensor doesn't have associated OF
node devm_hwmon_device_register() returns error which ultimately causes
failure of the PHY driver's probe function.

Signed-off-by: Peter Mamonov <pmamonov@...il.com>
---
 drivers/thermal/of-thermal.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/thermal/of-thermal.c b/drivers/thermal/of-thermal.c
index dc5093be553e..34b0cc173f4a 100644
--- a/drivers/thermal/of-thermal.c
+++ b/drivers/thermal/of-thermal.c
@@ -493,7 +493,7 @@ thermal_zone_of_sensor_register(struct device *dev, int sensor_id, void *data,

 	if (!dev || !dev->of_node) {
 		of_node_put(np);
-		return ERR_PTR(-EINVAL);
+		return ERR_PTR(-ENODEV);
 	}

 	sensor_np = of_node_get(dev->of_node);
-- 
2.23.0