[PATCH net-next v3 1/1] net: phy: marvell: avoid bringing down fibre link when autoneg is bypassed

[Qingtao Cao]

On 88E151x the SGMII autoneg bypass mode defaults to be enabled. When it is
activated, the device assumes a link-up status with existing configuration
in BMCR, avoid bringing down the fibre link in this case

Test case:
1. Two 88E151x connected with SFP, both enable autoneg, link is up with
   speed 1000M
2. Disable autoneg on one device and explicitly set its speed to 1000M
3. The fibre link can still up with this change, otherwise not.

Signed-off-by: Qingtao Cao <qingtao.cao@xxxxxxxx>
---
 drivers/net/phy/marvell.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/net/phy/marvell.c b/drivers/net/phy/marvell.c
index 9964bf3dea2f..efc4b2317466 100644
--- a/drivers/net/phy/marvell.c
+++ b/drivers/net/phy/marvell.c
@@ -195,6 +195,10 @@
 
 #define MII_88E1510_MSCR_2		0x15
 
+#define MII_88E1510_FSCR2		0x1a
+#define MII_88E1510_FSCR2_BYPASS_ENABLE	BIT(6)
+#define MII_88E1510_FSCR2_BYPASS_STATUS	BIT(5)
+
 #define MII_VCT5_TX_RX_MDI0_COUPLING	0x10
 #define MII_VCT5_TX_RX_MDI1_COUPLING	0x11
 #define MII_VCT5_TX_RX_MDI2_COUPLING	0x12
@@ -1623,11 +1627,21 @@ static void fiber_lpa_mod_linkmode_lpa_t(unsigned long *advertising, u32 lpa)
 static int marvell_read_status_page_an(struct phy_device *phydev,
 				       int fiber, int status)
 {
+	int fscr2;
 	int lpa;
 	int err;
 
 	if (!(status & MII_M1011_PHY_STATUS_RESOLVED)) {
 		phydev->link = 0;
+		if (fiber) {
+			fscr2 = phy_read(phydev, MII_88E1510_FSCR2);
+			if (fscr2 < 0)
+				return fscr2;
+			if ((fscr2 & MII_88E1510_FSCR2_BYPASS_ENABLE) &&
+			    (fscr2 & MII_88E1510_FSCR2_BYPASS_STATUS) &&
+			    (genphy_read_status_fixed(phydev) == 0))
+				phydev->link = 1;
+		}
 		return 0;
 	}
 
-- 
2.34.1