[PATCH RFC] net/phy: fix Marvell PHYs probe failure when HWMON and THERMAL_OF are enabled

[PATCH RFC] net/phy: fix Marvell PHYs probe failure when HWMON and THERMAL_OF are enabled

[Peter Mamonov]

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@gmail.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

Re: [PATCH RFC] net/phy: fix Marvell PHYs probe failure when HWMON and THERMAL_OF are enabled

[Andrew Lunn]

On Thu, Sep 19, 2019 at 12:38:37AM +0300, Peter Mamonov wrote:
> 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.

Hi Peter

It probably affects more then Marvell PHYs.

> 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.

Your patch look sensible to me.

> I've sent it to the releveant maintainers three weeks 
> ago without any feedback yet.

Could you point me at the relevant mailing list archive?

      Thanks
	Andrew

Re: [PATCH RFC] net/phy: fix Marvell PHYs probe failure when HWMON and THERMAL_OF are enabled

[Peter Mamonov]

Hi, Andrew,

On Thu, Sep 19, 2019 at 04:50:16AM +0200, Andrew Lunn wrote:
> On Thu, Sep 19, 2019 at 12:38:37AM +0300, Peter Mamonov wrote:
> > 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.
> 
> Hi Peter
> 
> It probably affects more then Marvell PHYs.
> 
> > 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.
> 
> Your patch look sensible to me.
> 
> > I've sent it to the releveant maintainers three weeks 
> > ago without any feedback yet.
> 
> Could you point me at the relevant mailing list archive?

Here it is: https://marc.info/?l=linux-pm&m=156691695616377&w=2

Regards,
Peter

> 
>       Thanks
> 	Andrew

Re: [PATCH RFC] net/phy: fix Marvell PHYs probe failure when HWMON and THERMAL_OF are enabled

[Andrew Lunn]

On Thu, Sep 19, 2019 at 11:10:56AM +0300, Peter Mamonov wrote:
> Hi, Andrew,
> 
> On Thu, Sep 19, 2019 at 04:50:16AM +0200, Andrew Lunn wrote:
> > On Thu, Sep 19, 2019 at 12:38:37AM +0300, Peter Mamonov wrote:
> > > 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.
> > 
> > Hi Peter
> > 
> > It probably affects more then Marvell PHYs.
> > 
> > > 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.
> > 
> > Your patch look sensible to me.
> > 
> > > I've sent it to the releveant maintainers three weeks 
> > > ago without any feedback yet.
> > 
> > Could you point me at the relevant mailing list archive?
> 
> Here it is: https://marc.info/?l=linux-pm&m=156691695616377&w=2

Hi Peter

O.K. Thanks.

We should not take this patch via netdev, since it is outside of
netdev, even if it does break netdev. So lets polish the patch a bit,
and then repost it to linux-pm and its maintainers.

Please could you add a Fixes: tag. Can you figure out which commit
broke it, or has it always been broken?

Add a stable: tag, indicating it needs to be back ported. For netdev,
you would not do this, but for linux-pm, i guess it is needed.

Change the subject a little. thermal: Fix broken registration if sensor OF node missing.

Add

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

When you post it, please Cc: me, netdev, davem, but make the To: the
three thermal maintainers.

Thanks
      Andrew