[PATCH net 1/1] net: phy: marvell: add link status check before enabling phy loopback

[Aminuddin Jamaluddin]

Add link status checking in m88e1510_loopback() for 1Gbps link speed
and delay for 100ms after phy loopback bit is set before send packet.
This is needed to ensure the stability and consistency when running
the phy loopback test.

Fixes: 020a45aff119 ("net: phy: marvell: add Marvell specific PHY loopback")
Cc: <stable@xxxxxxxxxxxxxxx> # 5.15.x
Signed-off-by: Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@xxxxxxxxx>
Signed-off-by: Aminuddin Jamaluddin <aminuddin.jamaluddin@xxxxxxxxx>
---
 drivers/net/phy/marvell.c | 22 ++++++++++++++++------
 include/linux/phy.h       |  3 +++
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/drivers/net/phy/marvell.c b/drivers/net/phy/marvell.c
index a714150f5e8c..17403acf780d 100644
--- a/drivers/net/phy/marvell.c
+++ b/drivers/net/phy/marvell.c
@@ -1992,6 +1992,7 @@ static int m88e1510_loopback(struct phy_device *phydev, bool enable)
 
 	if (enable) {
 		u16 bmcr_ctl, mscr2_ctl = 0;
+		int val = 0;
 
 		bmcr_ctl = mii_bmcr_encode_fixed(phydev->speed, phydev->duplex);
 
@@ -2015,14 +2016,23 @@ static int m88e1510_loopback(struct phy_device *phydev, bool enable)
 		if (err < 0)
 			return err;
 
-		/* FIXME: Based on trial and error test, it seem 1G need to have
-		 * delay between soft reset and loopback enablement.
-		 */
-		if (phydev->speed == SPEED_1000)
-			msleep(1000);
+		if (phydev->speed == SPEED_1000) {
+			err = phy_read_poll_timeout(phydev, MII_BMSR, val, val & BMSR_LSTATUS,
+						    PHY_LOOP_BACK_SLEEP,
+						    PHY_LOOP_BACK_TIMEOUT, true);
+			if (err)
+				return err;
+		}
 
-		return phy_modify(phydev, MII_BMCR, BMCR_LOOPBACK,
+		err =  phy_modify(phydev, MII_BMCR, BMCR_LOOPBACK,
 				  BMCR_LOOPBACK);
+		if (!err) {
+			/* It takes some time for PHY device to switch
+			 * into/out-of loopback mode.
+			 */
+			msleep(100);
+		}
+		return err;
 	} else {
 		err = phy_modify(phydev, MII_BMCR, BMCR_LOOPBACK, 0);
 		if (err < 0)
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 87638c55d844..b4da968da8e6 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -276,6 +276,9 @@ static inline const char *phy_modes(phy_interface_t interface)
 #define PHY_INIT_TIMEOUT	100000
 #define PHY_FORCE_TIMEOUT	10
 
+#define PHY_LOOP_BACK_SLEEP	1000000
+#define PHY_LOOP_BACK_TIMEOUT	8000000
+
 #define PHY_MAX_ADDR	32
 
 /* Used when trying to connect to a specific phy (mii bus id:phy device id) */
-- 
2.17.1