[PATCHv3 net-next] net: fec: Ensure clocks are enabled while using mdio bus

[Andrew Lunn]

When a switch is attached to the mdio bus, the mdio bus can be used
while the interface is not open. If the IPG clock are not enabled,
MDIO reads/writes will simply time out. So enable the clock before
starting a transaction, and disable it afterwards. The CCF performs
reference counting so the clock will only be disabled if there are no
other users.

Signed-off-by: Andrew Lunn <and...@lunn.ch>
---

v3:
 Return the error code from clk_prepare_enable()
v2:
 Only enable the IGP clock.

 drivers/net/ethernet/freescale/fec_main.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec_main.c 
b/drivers/net/ethernet/freescale/fec_main.c
index bf4cf3fbb5f2..8d9b1fd175f7 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -65,6 +65,7 @@
 
 static void set_multicast_list(struct net_device *ndev);
 static void fec_enet_itr_coal_init(struct net_device *ndev);
+static int fec_enet_clk_enable(struct net_device *ndev, bool enable);
 
 #define DRIVER_NAME    "fec"
 
@@ -1764,6 +1765,11 @@ static int fec_enet_mdio_read(struct mii_bus *bus, int 
mii_id, int regnum)
 {
        struct fec_enet_private *fep = bus->priv;
        unsigned long time_left;
+       int ret;
+
+       ret = clk_prepare_enable(fep->clk_ipg);
+       if (ret)
+               return ret;
 
        fep->mii_timeout = 0;
        init_completion(&fep->mdio_done);
@@ -1779,11 +1785,14 @@ static int fec_enet_mdio_read(struct mii_bus *bus, int 
mii_id, int regnum)
        if (time_left == 0) {
                fep->mii_timeout = 1;
                netdev_err(fep->netdev, "MDIO read timeout\n");
+               clk_disable_unprepare(fep->clk_ipg);
                return -ETIMEDOUT;
        }
 
-       /* return value */
-       return FEC_MMFR_DATA(readl(fep->hwp + FEC_MII_DATA));
+       ret = FEC_MMFR_DATA(readl(fep->hwp + FEC_MII_DATA));
+       clk_disable_unprepare(fep->clk_ipg);
+
+       return ret;
 }
 
 static int fec_enet_mdio_write(struct mii_bus *bus, int mii_id, int regnum,
@@ -1791,10 +1800,15 @@ static int fec_enet_mdio_write(struct mii_bus *bus, int 
mii_id, int regnum,
 {
        struct fec_enet_private *fep = bus->priv;
        unsigned long time_left;
+       int ret;
 
        fep->mii_timeout = 0;
        init_completion(&fep->mdio_done);
 
+       ret = clk_prepare_enable(fep->clk_ipg);
+       if (ret)
+               return ret;
+
        /* start a write op */
        writel(FEC_MMFR_ST | FEC_MMFR_OP_WRITE |
                FEC_MMFR_PA(mii_id) | FEC_MMFR_RA(regnum) |
@@ -1807,9 +1821,12 @@ static int fec_enet_mdio_write(struct mii_bus *bus, int 
mii_id, int regnum,
        if (time_left == 0) {
                fep->mii_timeout = 1;
                netdev_err(fep->netdev, "MDIO write timeout\n");
+               clk_disable_unprepare(fep->clk_ipg);
                return -ETIMEDOUT;
        }
 
+       clk_disable_unprepare(fep->clk_ipg);
+
        return 0;
 }
 
-- 
2.1.4

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