netdev - [PATCH v2 net 0/2] The DSA TX timestamping situation

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Date:   Sat, 28 Dec 2019 15:30:44 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     davem@...emloft.net, jakub.kicinski@...ronome.com
Cc:     richardcochran@...il.com, f.fainelli@...il.com,
        vivien.didelot@...il.com, andrew@...n.ch, claudiu.manoil@....com,
        yangbo.lu@....com, netdev@...r.kernel.org,
        Vladimir Oltean <olteanv@...il.com>
Subject: [PATCH v2 net 0/2] The DSA TX timestamping situation

This series is the moral v2 of "[PATCH net] net: dsa: sja1105: Fix
double delivery of TX timestamps to socket error queue" [0] which did
not manage to convince public opinion (actually it didn't convince me
neither).

This fixes PTP timestamping on one particular board, where the DSA
switch is sja1105 and the master is gianfar. Unfortunately there is no
way to make the fix more general without committing logical
inaccuracies: the SKBTX_IN_PROGRESS flag does serve a purpose, even if
the sja1105 driver is not using it now: it prevents delivering a SW
timestamp to the app socket when the HW timestamp will be provided. So
not setting this flag (the approach from v1) might create avoidable
complications in the future (not to mention that there isn't any
satisfactory explanation on why that would be the correct solution).

So the goal of this change set is to create a more strict framework for
DSA master devices when attached to PTP switches, and to fix the first
master driver that is overstepping its duties and is delivering
unsolicited TX timestamps.

[0]: https://www.spinics.net/lists/netdev/msg619699.html

Vladimir Oltean (2):
  gianfar: Fix TX timestamping with a stacked DSA driver
  net: dsa: Deny PTP on master if switch supports it

 drivers/net/ethernet/freescale/gianfar.c | 10 +++++---
 net/dsa/master.c                         | 30 ++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 3 deletions(-)

-- 
2.17.1