[PATCH net-next v2 4/4] net: fec: add support for PTP system timestamping for MDIO devices

[Hubert Feurstein]

From: Hubert Feurstein <h.feurstein@xxxxxxxxx>

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@xxxxxxxxx>
---
 drivers/net/ethernet/freescale/fec_main.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index c01d3ec3e9af..dd1253683ac0 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,
@@ -1956,7 +1958,7 @@ static int fec_enet_mii_init(struct platform_device *pdev)
 	struct fec_enet_private *fep = netdev_priv(ndev);
 	struct device_node *node;
 	int err = -ENXIO;
-	u32 mii_speed, holdtime;
+	u32 mii_speed, mii_period, holdtime;
 
 	/*
 	 * The i.MX28 dual fec interfaces are not equal.
@@ -1993,6 +1995,7 @@ static int fec_enet_mii_init(struct platform_device *pdev)
 	 * document.
 	 */
 	mii_speed = DIV_ROUND_UP(clk_get_rate(fep->clk_ipg), 5000000);
+	mii_period = div_u64((u64)mii_speed * 2 * NSEC_PER_SEC, clk_get_rate(fep->clk_ipg));
 	if (fep->quirks & FEC_QUIRK_ENET_MAC)
 		mii_speed--;
 	if (mii_speed > 63) {
@@ -2034,6 +2037,8 @@ 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->flags = MII_BUS_F_PTP_STS_SUPPORTED;
+	fep->mii_bus->ptp_sts_offset = 32 * mii_period;
 
 	node = of_get_child_by_name(pdev->dev.of_node, "mdio");
 	err = of_mdiobus_register(fep->mii_bus, node);
-- 
2.22.1