1 files changed, 27 insertions, 3 deletions

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index 78e1ce09b1ab..f6a3a7abd468 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -1954,6 +1954,7 @@ static int fec_enet_mii_init(struct platform_device *pdev)
         struct fec_enet_private *fep = netdev_priv(ndev);
         struct device_node *node;
         int err = -ENXIO, i;
+        u32 mii_speed, holdtime;
 
         /*
          * The i.MX28 dual fec interfaces are not equal.
@@ -1991,10 +1992,33 @@ static int fec_enet_mii_init(struct platform_device *pdev)
          * Reference Manual has an error on this, and gets fixed on i.MX6Q
          * document.
          */
-        fep->phy_speed = DIV_ROUND_UP(clk_get_rate(fep->clk_ipg), 5000000);
+        mii_speed = DIV_ROUND_UP(clk_get_rate(fep->clk_ipg), 5000000);
         if (fep->quirks & FEC_QUIRK_ENET_MAC)
-                fep->phy_speed--;
-        fep->phy_speed <<= 1;
+                mii_speed--;
+        if (mii_speed > 63) {
+                dev_err(&pdev->dev,
+                        "fec clock (%lu) to fast to get right mii speed\n",
+                        clk_get_rate(fep->clk_ipg));
+                err = -EINVAL;
+                goto err_out;
+        }
+
+        /*
+         * The i.MX28 and i.MX6 types have another filed in the MSCR (aka
+         * MII_SPEED) register that defines the MDIO output hold time. Earlier
+         * versions are RAZ there, so just ignore the difference and write the
+         * register always.
+         * The minimal hold time according to IEE802.3 (clause 22) is 10 ns.
+         * HOLDTIME + 1 is the number of clk cycles the fec is holding the
+         * output.
+         * The HOLDTIME bitfield takes values between 0 and 7 (inclusive).
+         * Given that ceil(clkrate / 5000000) <= 64, the calculation for
+         * holdtime cannot result in a value greater than 3.
+         */
+        holdtime = DIV_ROUND_UP(clk_get_rate(fep->clk_ipg), 100000000) - 1;
+
+        fep->phy_speed = mii_speed << 1 | holdtime << 8;
+
         writel(fep->phy_speed, fep->hwp + FEC_MII_SPEED);
 
         fep->mii_bus = mdiobus_alloc();