netdev - RE: bug: 'ethtool -m' reports spurious alarm & warning threshold values for QSFP28 transceivers

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Date:   Thu, 27 Sep 2018 20:17:28 +0000
From:   Chris Preimesberger <chrisp@...nsition.com>
To:     'Andrew Lunn' <andrew@...n.ch>,
        'Eran Ben Elisha' <eranbe@...lanox.com>
CC:     'Neil Horman' <nhorman@...driver.com>,
        "'linville@...driver.com'" <linville@...driver.com>,
        "'netdev@...r.kernel.org'" <netdev@...r.kernel.org>
Subject: RE: bug: 'ethtool -m' reports spurious alarm & warning threshold
 values for QSFP28 transceivers

Update for posterity-

Mellanox support provided a work-around of using mlxcables instead of
ethtool to read alarm/warning info for an installed transceiver.

I was told that a couple of their engineers are currently looking into the
discrepancy between threshold reporting by mlxcables and ethtool, and
that they are deciding what to do about it...

Work-around steps:
1. add a cable with "sudo mst cable add".
2. find the cable name with "sudo mlxcables".  The name of my cable is
   01:00.0_cable_0 so I copy that name for insertion into the next command.
3. probe the cable for DDM with "sudo mlxcables -d 01:00.0_cable_0 --DDM".


Example copied/pasted from my CLI here.
All reported thresholds appear to be correct.

tech1@D7:~$ 
tech1@D7:~$ 
tech1@D7:~$ sudo mst cable add
-I- Added 1 cable devices ..
tech1@D7:~$ sudo mlxcables
Querying Cables ....

Cable #1:
---------
Cable name    : 01:00.0_cable_0
>> No FW data to show
-------- Cable EEPROM --------
Identifier    : QSFP28 (11h)
Technology    : 850 nm VCSEL (00h)
Compliance    : Extended Specification Compliance is valid, 100GBASE-SR4 or 25GBASE-SR
Wavelength    : 850 nm
OUI           : 0x00c0f2
Vendor        : TRANSITION      
Serial number : TN02000263      
Part number   : TN-QSFP-100G-SR4
Revision      : 02
Temperature   : 34 C
Length        : 50 m

tech1@D7:~$ sudo mlxcables -d 01:00.0_cable_0 --DDM
Cable DDM:
----------
Temperature    : 34C
Voltage        : 3.2918V
Channel 1:
	RX Power : 0.1695dBm
	TX Power : 0.8622dBm
	TX Bias  : 7.0720mA
Channel 2:
	RX Power : 0.1355dBm
	TX Power : 1.1042dBm
	TX Bias  : 6.9240mA
Channel 3:
	RX Power : -0.1592dBm
	TX Power : 0.6547dBm
	TX Bias  : 6.9420mA
Channel 4:
	RX Power : -0.1300dBm
	TX Power : 0.4653dBm
	TX Bias  : 6.9120mA
----- Thresholds -----
Temperature:
	High Warning  : 70C
	Low  Warning  : 0C
	High Alarm    : 75C
	Low  Alarm    : -5C
	Warning mask  : 0
	Alarm mask    : 0
Voltage:
	High Warning : 3.4600V
	Low  Warning : 3.1300V
	High Alarm   : 3.6300V
	Low  Alarm   : 2.9700V
	Warning mask : 0
	Alarm mask   : 0
Channel 1:
	RX Power high warn   : 2.4000dBm
	RX Power low  warn   : -9.5001dBm
	RX Power high alarm  : 5.4103dBm
	RX Power low  alarm  : -12.5104dBm
	RX Power Warning mask: 0
	RX Power Alarm mask  : 0
	TX Power high warn   : 2.4000dBm
	TX Power low  warn   : -7.6020dBm
	TX Power high alarm  : 3.1917dBm
	TX Power low  alarm  : -8.5699dBm
	TX Power Warning mask: 0
	TX Power Alarm mask  : 0
	TX Bias high warn    : 12.0000mA
	TX Bias low  warn    : 2.0000mA
	TX Bias high alarm   : 15.0000mA
	TX Bias low  alarm   : 1.0000mA
	TX Bias Warning mask : 0
	TX Bias Alarm mask   : 0
Channel 2:
	RX Power high warn   : 2.4000dBm
	RX Power low  warn   : -9.5001dBm
	RX Power high alarm  : 5.4103dBm
	RX Power low  alarm  : -12.5104dBm
	RX Power Warning mask: 0
	RX Power Alarm mask  : 0
	TX Power high warn   : 2.4000dBm
	TX Power low  warn   : -7.6020dBm
	TX Power high alarm  : 3.1917dBm
	TX Power low  alarm  : -8.5699dBm
	TX Power Warning mask: 0
	TX Power Alarm mask  : 0
	TX Bias high warn    : 12.0000mA
	TX Bias low  warn    : 2.0000mA
	TX Bias high alarm   : 15.0000mA
	TX Bias low  alarm   : 1.0000mA
	TX Bias Warning mask : 0
	TX Bias Alarm mask   : 0
Channel 3:
	RX Power high warn   : 2.4000dBm
	RX Power low  warn   : -9.5001dBm
	RX Power high alarm  : 5.4103dBm
	RX Power low  alarm  : -12.5104dBm
	RX Power Warning mask: 0
	RX Power Alarm mask  : 0
	TX Power high warn   : 2.4000dBm
	TX Power low  warn   : -7.6020dBm
	TX Power high alarm  : 3.1917dBm
	TX Power low  alarm  : -8.5699dBm
	TX Power Warning mask: 0
	TX Power Alarm mask  : 0
	TX Bias high warn    : 12.0000mA
	TX Bias low  warn    : 2.0000mA
	TX Bias high alarm   : 15.0000mA
	TX Bias low  alarm   : 1.0000mA
	TX Bias Warning mask : 0
	TX Bias Alarm mask   : 0
Channel 4:
	RX Power high warn   : 2.4000dBm
	RX Power low  warn   : -9.5001dBm
	RX Power high alarm  : 5.4103dBm
	RX Power low  alarm  : -12.5104dBm
	RX Power Warning mask: 0
	RX Power Alarm mask  : 0
	TX Power high warn   : 2.4000dBm
	TX Power low  warn   : -7.6020dBm
	TX Power high alarm  : 3.1917dBm
	TX Power low  alarm  : -8.5699dBm
	TX Power Warning mask: 0
	TX Power Alarm mask  : 0
	TX Bias high warn    : 12.0000mA
	TX Bias low  warn    : 2.0000mA
	TX Bias high alarm   : 15.0000mA
	TX Bias low  alarm   : 1.0000mA
	TX Bias Warning mask : 0
	TX Bias Alarm mask   : 0
tech1@D7:~$ 
tech1@D7:~$ 
tech1@D7:~$ 



Chris Preimesberger