[PATCH net] net: phy: sfp: hwmon: Fix scaling of RX power

[PATCH net] net: phy: sfp: hwmon: Fix scaling of RX power

[Andrew Lunn]

The RX power read from the SFP uses units of 0.1uW. This must be
scaled to units of uW for HWMON. This requires a divide by 10, not the
current 100.

With this change in place, sensors(1) and ethtool -m agree:

sff2-isa-0000
Adapter: ISA adapter
in0:          +3.23 V
temp1:        +33.1 C
power1:      270.00 uW
power2:      200.00 uW
curr1:        +0.01 A

        Laser output power                        : 0.2743 mW / -5.62 dBm
        Receiver signal average optical power     : 0.2014 mW / -6.96 dBm

Reported-by: chris.healy@zii.aero
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Fixes: 1323061a018a ("net: phy: sfp: Add HWMON support for module sensors")
---
 drivers/net/phy/sfp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
index 2d816aadea79..e36c04c26866 100644
--- a/drivers/net/phy/sfp.c
+++ b/drivers/net/phy/sfp.c
@@ -517,7 +517,7 @@ static int sfp_hwmon_read_sensor(struct sfp *sfp, int reg, long *value)
 
 static void sfp_hwmon_to_rx_power(long *value)
 {
-	*value = DIV_ROUND_CLOSEST(*value, 100);
+	*value = DIV_ROUND_CLOSEST(*value, 10);
 }
 
 static void sfp_hwmon_calibrate(struct sfp *sfp, unsigned int slope, int offset,
-- 
2.20.1

Re: [PATCH net] net: phy: sfp: hwmon: Fix scaling of RX power

[David Miller]

From: Andrew Lunn <andrew@lunn.ch>
Date: Sun, 21 Jul 2019 18:50:08 +0200

> The RX power read from the SFP uses units of 0.1uW. This must be
> scaled to units of uW for HWMON. This requires a divide by 10, not the
> current 100.
> 
> With this change in place, sensors(1) and ethtool -m agree:
> 
> sff2-isa-0000
> Adapter: ISA adapter
> in0:          +3.23 V
> temp1:        +33.1 C
> power1:      270.00 uW
> power2:      200.00 uW
> curr1:        +0.01 A
> 
>         Laser output power                        : 0.2743 mW / -5.62 dBm
>         Receiver signal average optical power     : 0.2014 mW / -6.96 dBm
> 
> Reported-by: chris.healy@zii.aero
> Signed-off-by: Andrew Lunn <andrew@lunn.ch>
> Fixes: 1323061a018a ("net: phy: sfp: Add HWMON support for module sensors")

Applied and queued up for -stable, thanks Andrew.