netdev - [PATCH net-next 3/3] net: fec: add support for PTP system timestamping for MDIO devices

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Date:   Fri, 16 Aug 2019 18:31:57 +0200
From:   Hubert Feurstein <h.feurstein@...il.com>
To:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Hubert Feurstein <h.feurstein@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Richard Cochran <richardcochran@...il.com>,
        Fugang Duan <fugang.duan@....com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH net-next 3/3] net: fec: add support for PTP system timestamping for MDIO devices

In order to improve the synchronisation precision of phc2sys (from
the linuxptp project) for devices like switches which are attached
to the MDIO bus, it is necessary the get the system timestamps as
close as possible to the access which causes the PTP timestamp
register to be snapshotted in the switch hardware. Usually this is
triggered by an MDIO write access, the snapshotted timestamp is then
transferred by several MDIO reads.

The ptp_read_system_*ts functions already check the ptp_sts pointer.

Signed-off-by: Hubert Feurstein <h.feurstein@...il.com>
---
 drivers/net/ethernet/freescale/fec_main.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index 2f6057e7335d..60e866631b61 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -1815,10 +1815,12 @@ static int fec_enet_mdio_write(struct mii_bus *bus, int mii_id, int regnum,
 	reinit_completion(&fep->mdio_done);
 
 	/* start a write op */
+	ptp_read_system_prets(bus->ptp_sts);
 	writel(FEC_MMFR_ST | FEC_MMFR_OP_WRITE |
 		FEC_MMFR_PA(mii_id) | FEC_MMFR_RA(regnum) |
 		FEC_MMFR_TA | FEC_MMFR_DATA(value),
 		fep->hwp + FEC_MII_DATA);
+	ptp_read_system_postts(bus->ptp_sts);
 
 	/* wait for end of transfer */
 	time_left = wait_for_completion_timeout(&fep->mdio_done,
@@ -2034,6 +2036,7 @@ static int fec_enet_mii_init(struct platform_device *pdev)
 		pdev->name, fep->dev_id + 1);
 	fep->mii_bus->priv = fep;
 	fep->mii_bus->parent = &pdev->dev;
+	fep->mii_bus->ptp_sts_supported = true;
 
 	node = of_get_child_by_name(pdev->dev.of_node, "mdio");
 	err = of_mdiobus_register(fep->mii_bus, node);
-- 
2.22.1