From: Andrew Lunn <andrew@lunn.ch>
To: Michael Walle <michael@walle.cc>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
Florian Fainelli <f.fainelli@gmail.com>,
Heiner Kallweit <hkallweit1@gmail.com>,
Russell King <linux@armlinux.org.uk>,
"David S . Miller" <davem@davemloft.net>,
Richard Cochran <richardcochran@gmail.com>
Subject: Re: [RFC PATCH 0/2] AT8031 PHY timestamping support
Date: Wed, 26 Feb 2020 00:50:40 +0100 [thread overview]
Message-ID: <20200225235040.GF9749@lunn.ch> (raw)
In-Reply-To: <20200225230819.7325-1-michael@walle.cc>
On Wed, Feb 26, 2020 at 12:08:17AM +0100, Michael Walle wrote:
> This patchset is the current state of my work for adding PHY timestamping
> support. I just wanted to post this to the mailinglist before I never do
> it. Maybe its a starting point for other people. That being said, I
> wouldn't mind comments ;) The code basically works but there are three
> major caveats:
>
> (1) The reading of timestamps via MDIO sometimes return wrong values. What
> I see is that a part of the timestamp corresponds to the new timestamp
> while another part still contains old values. Thus at the moment, I'm
> reading the registers twice. I don't know if the reading actually
> affects the update of the timestamp or the different timing (my MDIO
> bus is rather slow, so reading the timestamp a second time take some
> amount of time; but I've also tested with some delays and it didn't
> had any effects). There is also no possibility to read the timestamp
> atomically :(
Hi Michael
That sounds fundamentally broken. Which would be odd. Sometimes there
is a way to take a snapshot of the value. Reading the first word could
trigger this snapshot. Or the last word, or some status register. One
would hope the datasheet would talk about this.
Andrew
next prev parent reply other threads:[~2020-02-25 23:50 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-25 23:08 [RFC PATCH 0/2] AT8031 PHY timestamping support Michael Walle
2020-02-25 23:08 ` [RFC PATCH 1/2] net: phy: let the driver register its own IRQ handler Michael Walle
2020-02-26 7:27 ` Heiner Kallweit
2020-02-26 11:12 ` Michael Walle
2020-02-26 21:17 ` Heiner Kallweit
2020-02-26 22:56 ` Michael Walle
2020-02-25 23:08 ` [RFC PATCH 2/2] net: phy: at803x: add PTP support for AR8031 Michael Walle
2020-02-25 23:50 ` Andrew Lunn [this message]
2020-02-26 0:07 ` [RFC PATCH 0/2] AT8031 PHY timestamping support Michael Walle
2020-02-26 2:54 ` Richard Cochran
2020-02-26 11:30 ` Michael Walle
2020-02-26 14:29 ` Richard Cochran
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