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Date: Wed, 26 Feb 2020 00:08:17 +0100 From: Michael Walle <michael@...le.cc> To: netdev@...r.kernel.org, linux-kernel@...r.kernel.org Cc: Andrew Lunn <andrew@...n.ch>, Florian Fainelli <f.fainelli@...il.com>, Heiner Kallweit <hkallweit1@...il.com>, Russell King <linux@...linux.org.uk>, "David S . Miller" <davem@...emloft.net>, Richard Cochran <richardcochran@...il.com>, Michael Walle <michael@...le.cc> Subject: [RFC PATCH 0/2] AT8031 PHY timestamping support 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 :( (2) It seems to be the case that the PHY generates an interrupt on every PTP message, eg. even if it is not an event message meaning that a new timestamp is ready. Thus we might read the timestamp too often. (3) Sometimes the TX timestamp is missing. It seems that in this case the PHY doesn't generate an interrupt. If you check for any RX_PTP/TX_PTP interrupt pending and then read both timestamps (remember that get_rxts/get_txts checks that the timestamp has actually changed) it seems to work though. if (mask & (AT8031_INTR_RX_PTP | AT8031_INTR_TX_PTP)) { at8031_get_rxts(phydev); at8031_get_txts(phydev); } Please note that the patch doesn't contain the code above. Replacing the IRQ handling with the code make PTP actually work, but I'm not satisfied with that solution, esp. reading the timestamps multiple times over MDIO. So currently I'm stuck and unfortunately, I'm not able to get support from Atheros/our FAE. The PHY also supports appending the timestamp to the actual ethernet frame, but this seems to only work when the PHY is connected via RGMII. I've never get it to work with a SGMII connection. The first patch might actually be useful outside of this series. See also https://lore.kernel.org/netdev/bd47f8e1ebc04fa98856ed8d89b91419@walle.cc/ -michael Michael Walle (2): net: phy: let the driver register its own IRQ handler net: phy: at803x: add PTP support for AR8031 drivers/net/phy/Kconfig | 17 + drivers/net/phy/at803x.c | 879 ++++++++++++++++++++++++++++++++++- drivers/net/phy/phy.c | 15 + drivers/net/phy/phy_device.c | 6 +- include/linux/phy.h | 2 + 5 files changed, 892 insertions(+), 27 deletions(-) -- 2.20.1
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