From: Andrew Lunn <andrew@lunn.ch>
To: Miroslav Lichvar <mlichvar@redhat.com>
Cc: Hubert Feurstein <h.feurstein@gmail.com>,
netdev <netdev@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
Richard Cochran <richardcochran@gmail.com>,
Florian Fainelli <f.fainelli@gmail.com>,
Heiner Kallweit <hkallweit1@gmail.com>,
Vladimir Oltean <olteanv@gmail.com>,
"David S. Miller" <davem@davemloft.net>
Subject: Re: [PATCH net-next v3 2/4] net: mdio: add PTP offset compensation to mdiobus_write_sts
Date: Tue, 20 Aug 2019 17:23:06 +0200 [thread overview]
Message-ID: <20190820152306.GJ29991@lunn.ch> (raw)
In-Reply-To: <20190820142537.GL891@localhost>
> - take a second "post" system timestamp after the completion
For this hardware, completion is an interrupt, which has a lot of
jitter on it. But this hardware is odd, in that it uses an
interrupt. Every other MDIO bus controller uses polled IO, with an
mdelay(10) or similar between each poll. So the jitter is going to be
much larger.
Even though the FEC is special with its interrupt completion, i would
like to see the solution being reasonably generic so that others can
copy it into other MDIO bus drivers. That is what is nice about taking
the time stamp around the write which triggers the bus transaction. It
is independent of interrupt or polled, and should mean about the same
thing for different vendors hardware.
Andrew
next prev parent reply other threads:[~2019-08-20 15:23 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-20 8:48 [PATCH net-next v3 0/4] Improve phc2sys precision for mv88e6xxx switch in combination with imx6-fec Hubert Feurstein
2019-08-20 8:48 ` [PATCH net-next v3 1/4] net: mdio: add support for passing a PTP system timestamp to the mii_bus driver Hubert Feurstein
2019-08-20 8:48 ` [PATCH net-next v3 2/4] net: mdio: add PTP offset compensation to mdiobus_write_sts Hubert Feurstein
2019-08-20 9:49 ` Miroslav Lichvar
2019-08-20 12:29 ` Hubert Feurstein
2019-08-20 14:25 ` Miroslav Lichvar
2019-08-20 15:23 ` Andrew Lunn [this message]
2019-08-20 15:40 ` Miroslav Lichvar
2019-08-20 16:56 ` Hubert Feurstein
2019-08-21 8:07 ` Miroslav Lichvar
2019-08-21 9:53 ` Hubert Feurstein
2019-08-21 10:19 ` Vladimir Oltean
2019-08-21 10:19 ` Miroslav Lichvar
2019-08-20 13:26 ` Andrew Lunn
2019-08-20 8:48 ` [PATCH net-next v3 3/4] net: dsa: mv88e6xxx: extend PTP gettime function to read system clock Hubert Feurstein
2019-08-20 8:48 ` [PATCH net-next v3 4/4] net: fec: add support for PTP system timestamping for MDIO devices Hubert Feurstein
2019-08-21 10:28 ` Vladimir Oltean
2019-08-22 3:49 ` [PATCH net-next v3 0/4] Improve phc2sys precision for mv88e6xxx switch in combination with imx6-fec David Miller
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