[PATCH net-next v1 3/4] net: phy: realtek: provide TimeSync data path delays for RTL8211E

[Oleksij Rempel]

Provide default data path delays for RTL8211E.

The measurements was done against with iMX8MP STMMAC and LAN8841 as the
link partner.

This values was calculated based on RGMII-PHY-PHY-RGMII measurements,
where the link partner is LAN8841. Following values was measured:
- data flow from RTL8211E to LAN8841:
  746ns @ 1000Mbps
  1770ns @ 100Mbps
  932000ns @ 10Mbps
- data flow from LAN8841 to RTL8211E:
  594ns @ 1000Mbps
  1130ns @ 100Mbps
  8920ns @ 10Mbps

Before this patch ptp4l reported following path delays:
~610ns @ 1000Mbps
~942ns @ 100Mbps
~465998ns @ 10Mbps

PPS offset compared to grand master was:
~ -114ns @ 1000Mbps
~ -215ns @ 100Mbps
~ -465998ns @ 10Mbps

Magnetic - Cable - Magnetic - delay in this setup was about 5ns.

Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
---
 drivers/net/phy/realtek.c | 42 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/drivers/net/phy/realtek.c b/drivers/net/phy/realtek.c
index 1fa70427b2a26..e39fec8d166b9 100644
--- a/drivers/net/phy/realtek.c
+++ b/drivers/net/phy/realtek.c
@@ -221,6 +221,47 @@ static int rtl8211e_config_intr(struct phy_device *phydev)
 	return err;
 }
 
+static int rtl8211e_get_timesync_data_path_delays(struct phy_device *phydev,
+						  struct phy_timesync_delay *tsd)
+{
+	phydev_warn(phydev, "Time stamping is not supported\n");
+
+	switch (phydev->interface) {
+	case PHY_INTERFACE_MODE_RGMII:
+	case PHY_INTERFACE_MODE_RGMII_RXID:
+	case PHY_INTERFACE_MODE_RGMII_TXID:
+	case PHY_INTERFACE_MODE_RGMII_ID:
+		/* The values are measured with RTL8211E and LAN8841 as link
+		 * partners and confirmed with i211 to be in sane range.
+		 */
+		if (phydev->speed == SPEED_1000) {
+			tsd->tx_min_delay_ns = 326;
+			tsd->rx_min_delay_ns = 406;
+			return 0;
+		} else if (phydev->speed == SPEED_100) {
+			tsd->tx_min_delay_ns = 703;
+			tsd->rx_min_delay_ns = 621;
+			return 0;
+		} else if (phydev->speed == SPEED_10) {
+			/* This value is suspiciously big, with atypical
+			 * shift to Egress side. This value is confirmed
+			 * by measuring RGMII-PHY-PHY-RGMII path delay.
+			 * Similar results are confirmed with LAN8841 and i211
+			 * as link partners.
+			 */
+			tsd->tx_min_delay_ns = 920231;
+			tsd->rx_min_delay_ns = 1674;
+			return 0;
+		}
+	default:
+		break;
+	}
+
+	phydev_warn(phydev, "Not tested or not supported modes for path delay values\n");
+
+	return -EOPNOTSUPP;
+}
+
 static int rtl8211f_config_intr(struct phy_device *phydev)
 {
 	u16 val;
@@ -935,6 +976,7 @@ static struct phy_driver realtek_drvs[] = {
 		.resume		= genphy_resume,
 		.read_page	= rtl821x_read_page,
 		.write_page	= rtl821x_write_page,
+		.get_timesync_data_path_delays = rtl8211e_get_timesync_data_path_delays,
 	}, {
 		PHY_ID_MATCH_EXACT(0x001cc916),
 		.name		= "RTL8211F Gigabit Ethernet",
-- 
2.39.2