phy: fix phy_id detection also for broken hardware.

This patch fixes the case when the phy_ids is mostly Fs and in some case 0x0
due to broken hardware.

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 2 deletions

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 55bc24b234e3..25acbbde4a60 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -227,8 +227,17 @@ struct phy_device * get_phy_device(struct mii_bus *bus, int addr)
         if (r)
                 return ERR_PTR(r);
 
-        /* If the phy_id is all Fs or all 0s, there is no device there */
-        if ((0xffff == phy_id) || (0x00 == phy_id))
+        /* If the phy_id is mostly Fs, there is no device there */
+        if ((phy_id & 0x1fffffff) == 0x1fffffff)
+                return NULL;
+
+        /*
+         * Broken hardware is sometimes missing the pull down resistor on the
+         * MDIO line, which results in reads to non-existent devices returning
+         * 0 rather than 0xffff. Catch this here and treat 0 as a non-existent
+         * device as well.
+         */
+        if (phy_id == 0)
                 return NULL;
 
         dev = phy_device_create(bus, addr, phy_id);