lxt PHY: Support for the buggy LXT973 rev A2

This patch adds proper handling of the buggy revision A2 of LXT973 phy, adding
precautions linked to ERRATA Item 4:

Revision A2 of LXT973 chip randomly returns the contents of the previous even
register when you read a odd register regularly

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 127 insertions, 0 deletions

diff --git a/drivers/net/phy/lxt.c b/drivers/net/phy/lxt.c
index 6d1e3fcc43e2..ec40ba882f61 100644
--- a/drivers/net/phy/lxt.c
+++ b/drivers/net/phy/lxt.c
@@ -122,6 +122,123 @@ static int lxt971_config_intr(struct phy_device *phydev)
         return err;
 }
 
+/*
+ * A2 version of LXT973 chip has an ERRATA: it randomly return the contents
+ * of the previous even register when you read a odd register regularly
+ */
+
+static int lxt973a2_update_link(struct phy_device *phydev)
+{
+        int status;
+        int control;
+        int retry = 8; /* we try 8 times */
+
+        /* Do a fake read */
+        status = phy_read(phydev, MII_BMSR);
+
+        if (status < 0)
+                return status;
+
+        control = phy_read(phydev, MII_BMCR);
+        if (control < 0)
+                return control;
+
+        do {
+                /* Read link and autonegotiation status */
+                status = phy_read(phydev, MII_BMSR);
+        } while (status >= 0 && retry-- && status == control);
+
+        if (status < 0)
+                return status;
+
+        if ((status & BMSR_LSTATUS) == 0)
+                phydev->link = 0;
+        else
+                phydev->link = 1;
+
+        return 0;
+}
+
+int lxt973a2_read_status(struct phy_device *phydev)
+{
+        int adv;
+        int err;
+        int lpa;
+        int lpagb = 0;
+
+        /* Update the link, but return if there was an error */
+        err = lxt973a2_update_link(phydev);
+        if (err)
+                return err;
+
+        if (AUTONEG_ENABLE == phydev->autoneg) {
+                int retry = 1;
+
+                adv = phy_read(phydev, MII_ADVERTISE);
+
+                if (adv < 0)
+                        return adv;
+
+                do {
+                        lpa = phy_read(phydev, MII_LPA);
+
+                        if (lpa < 0)
+                                return lpa;
+
+                        /* If both registers are equal, it is suspect but not
+                        * impossible, hence a new try
+                        */
+                } while (lpa == adv && retry--);
+
+                lpa &= adv;
+
+                phydev->speed = SPEED_10;
+                phydev->duplex = DUPLEX_HALF;
+                phydev->pause = phydev->asym_pause = 0;
+
+                if (lpagb & (LPA_1000FULL | LPA_1000HALF)) {
+                        phydev->speed = SPEED_1000;
+
+                        if (lpagb & LPA_1000FULL)
+                                phydev->duplex = DUPLEX_FULL;
+                } else if (lpa & (LPA_100FULL | LPA_100HALF)) {
+                        phydev->speed = SPEED_100;
+
+                        if (lpa & LPA_100FULL)
+                                phydev->duplex = DUPLEX_FULL;
+                } else {
+                        if (lpa & LPA_10FULL)
+                                phydev->duplex = DUPLEX_FULL;
+                }
+
+                if (phydev->duplex == DUPLEX_FULL) {
+                        phydev->pause = lpa & LPA_PAUSE_CAP ? 1 : 0;
+                        phydev->asym_pause = lpa & LPA_PAUSE_ASYM ? 1 : 0;
+                }
+        } else {
+                int bmcr = phy_read(phydev, MII_BMCR);
+
+                if (bmcr < 0)
+                        return bmcr;
+
+                if (bmcr & BMCR_FULLDPLX)
+                        phydev->duplex = DUPLEX_FULL;
+                else
+                        phydev->duplex = DUPLEX_HALF;
+
+                if (bmcr & BMCR_SPEED1000)
+                        phydev->speed = SPEED_1000;
+                else if (bmcr & BMCR_SPEED100)
+                        phydev->speed = SPEED_100;
+                else
+                        phydev->speed = SPEED_10;
+
+                phydev->pause = phydev->asym_pause = 0;
+        }
+
+        return 0;
+}
+
 static int lxt973_probe(struct phy_device *phydev)
 {
         int val = phy_read(phydev, MII_LXT973_PCR);
@@ -175,6 +292,16 @@ static struct phy_driver lxt97x_driver[] = {
         .driver         = { .owner = THIS_MODULE,},
 }, {
         .phy_id         = 0x00137a10,
+        .name           = "LXT973-A2",
+        .phy_id_mask    = 0xffffffff,
+        .features       = PHY_BASIC_FEATURES,
+        .flags          = 0,
+        .probe          = lxt973_probe,
+        .config_aneg    = lxt973_config_aneg,
+        .read_status    = lxt973a2_read_status,
+        .driver         = { .owner = THIS_MODULE,},
+}, {
+        .phy_id         = 0x00137a10,
         .name           = "LXT973",
         .phy_id_mask    = 0xfffffff0,
         .features       = PHY_BASIC_FEATURES,