net: pcs: xpcs: fix incorrect CL37 AN sequence

According to Synopsys DesignWare Cores Ethernet PCS databook, it is
required to disable Clause 37 auto-negotiation by programming bit-12
(AN_ENABLE) to 0 if it is already enabled, before programming various
fields of VR_MII_AN_CTRL registers.

After all these programming are done, it is then required to enable
Clause 37 auto-negotiation by programming bit-12 (AN_ENABLE) to 1.

Fixes: b97b5331b8ab ("net: pcs: add C37 SGMII AN support for intel mGbE controller")
Cc: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Wong Vee Khee <vee.khee.wong@linux.intel.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Tested-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/pcs/pcs-xpcs.c b/drivers/net/pcs/pcs-xpcs.c
index fb0a83d..a3e806c 100644 (file)
--- a/drivers/net/pcs/pcs-xpcs.c
+++ b/drivers/net/pcs/pcs-xpcs.c
@@ -697,14 +697,17 @@ EXPORT_SYMBOL_GPL(xpcs_config_eee);
 
 static int xpcs_config_aneg_c37_sgmii(struct dw_xpcs *xpcs, unsigned int mode)
 {
-       int ret;
+       int ret, mdio_ctrl;
 
        /* For AN for C37 SGMII mode, the settings are :-
-        * 1) VR_MII_AN_CTRL Bit(2:1)[PCS_MODE] = 10b (SGMII AN)
-        * 2) VR_MII_AN_CTRL Bit(3) [TX_CONFIG] = 0b (MAC side SGMII)
+        * 1) VR_MII_MMD_CTRL Bit(12) [AN_ENABLE] = 0b (Disable SGMII AN in case
+             it is already enabled)
+        * 2) VR_MII_AN_CTRL Bit(2:1)[PCS_MODE] = 10b (SGMII AN)
+        * 3) VR_MII_AN_CTRL Bit(3) [TX_CONFIG] = 0b (MAC side SGMII)
         *    DW xPCS used with DW EQoS MAC is always MAC side SGMII.
-        * 3) VR_MII_DIG_CTRL1 Bit(9) [MAC_AUTO_SW] = 1b (Automatic
+        * 4) VR_MII_DIG_CTRL1 Bit(9) [MAC_AUTO_SW] = 1b (Automatic
         *    speed/duplex mode change by HW after SGMII AN complete)
+        * 5) VR_MII_MMD_CTRL Bit(12) [AN_ENABLE] = 1b (Enable SGMII AN)
         *
         * Note: Since it is MAC side SGMII, there is no need to set
         *       SR_MII_AN_ADV. MAC side SGMII receives AN Tx Config from
@@ -712,6 +715,17 @@ static int xpcs_config_aneg_c37_sgmii(struct dw_xpcs *xpcs, unsigned int mode)
         *       between PHY and Link Partner. There is also no need to
         *       trigger AN restart for MAC-side SGMII.
         */
+       mdio_ctrl = xpcs_read(xpcs, MDIO_MMD_VEND2, DW_VR_MII_MMD_CTRL);
+       if (mdio_ctrl < 0)
+               return mdio_ctrl;
+
+       if (mdio_ctrl & AN_CL37_EN) {
+               ret = xpcs_write(xpcs, MDIO_MMD_VEND2, DW_VR_MII_MMD_CTRL,
+                                mdio_ctrl & ~AN_CL37_EN);
+               if (ret < 0)
+                       return ret;
+       }
+
        ret = xpcs_read(xpcs, MDIO_MMD_VEND2, DW_VR_MII_AN_CTRL);
        if (ret < 0)
                return ret;
@@ -736,7 +750,15 @@ static int xpcs_config_aneg_c37_sgmii(struct dw_xpcs *xpcs, unsigned int mode)
        else
                ret &= ~DW_VR_MII_DIG_CTRL1_MAC_AUTO_SW;
 
-       return xpcs_write(xpcs, MDIO_MMD_VEND2, DW_VR_MII_DIG_CTRL1, ret);
+       ret = xpcs_write(xpcs, MDIO_MMD_VEND2, DW_VR_MII_DIG_CTRL1, ret);
+       if (ret < 0)
+               return ret;
+
+       if (phylink_autoneg_inband(mode))
+               ret = xpcs_write(xpcs, MDIO_MMD_VEND2, DW_VR_MII_MMD_CTRL,
+                                mdio_ctrl | AN_CL37_EN);
+
+       return ret;
 }
 
 static int xpcs_config_2500basex(struct dw_xpcs *xpcs)