[PATCH 2/3] net: socionext: Add dummy PHY register read in phy_write()

[masahisa . kojima]

From: Masahisa Kojima <masahisa.koj...@linaro.org>

There is a compatibility issue between RTL8211E implemented
in Developerbox and netsec network controller IP(F_GMAC4).

RTL8211E expects MDC clock must be kept toggling for several
clock cycle with MDIO high before entering the IDLE state.
To meet this requirement, netsec driver needs to issue dummy
read(e.g. read PHYID1(offset 0x2) register) right after write.

Signed-off-by: Masahisa Kojima <masahisa.koj...@linaro.org>
Signed-off-by: Yoshitoyo Osaki <osaki.yoshit...@socionext.com>
---
 drivers/net/ethernet/socionext/netsec.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/socionext/netsec.c 
b/drivers/net/ethernet/socionext/netsec.c
index 273cc5fc07e0..e7faaf8be99e 100644
--- a/drivers/net/ethernet/socionext/netsec.c
+++ b/drivers/net/ethernet/socionext/netsec.c
@@ -431,9 +431,12 @@ static int netsec_mac_update_to_phy_state(struct 
netsec_priv *priv)
        return 0;
 }
 
+static int netsec_phy_read(struct mii_bus *bus, int phy_addr, int reg_addr);
+
 static int netsec_phy_write(struct mii_bus *bus,
                            int phy_addr, int reg, u16 val)
 {
+       int status;
        struct netsec_priv *priv = bus->priv;
 
        if (netsec_mac_write(priv, GMAC_REG_GDR, val))
@@ -446,8 +449,19 @@ static int netsec_phy_write(struct mii_bus *bus,
                              GMAC_REG_SHIFT_CR_GAR)))
                return -ETIMEDOUT;
 
-       return netsec_mac_wait_while_busy(priv, GMAC_REG_GAR,
-                                         NETSEC_GMAC_GAR_REG_GB);
+       status = netsec_mac_wait_while_busy(priv, GMAC_REG_GAR,
+                                           NETSEC_GMAC_GAR_REG_GB);
+
+       /* Developerbox implements RTL8211E PHY and there is
+        * a compatibility problem with F_GMAC4.
+        * RTL8211E expects MDC clock must be kept toggling for several
+        * clock cycle with MDIO high before entering the IDLE state.
+        * To meet this requirement, netsec driver needs to issue dummy
+        * read(e.g. read PHYID1(offset 0x2) register) right after write.
+        */
+       netsec_phy_read(bus, phy_addr, 2);
+
+       return status;
 }
 
 static int netsec_phy_read(struct mii_bus *bus, int phy_addr, int reg_addr)
-- 
2.14.2