usb-net/pegasus: fix pegasus carrier detection

Broken by 4a1728a28a193aa388900714bbb1f375e08a6d8e which switched the
return semantics of read_mii_word() but didn't fix usage of
read_mii_word() to conform to the new semantics.

Setting carrier to off based on the NO_CARRIER flag is also incorrect as
that flag only triggers on TX failure and therefore isn't correct when
no frames are being transmitted.  Since there is already a 2*HZ MII
carrier check going on, defer to that.

Add a TRUST_LINK_STATUS feature flag for adapters where the LINK_STATUS
flag is actually correct, and use that rather than the NO_CARRIER flag.

Signed-off-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 12 insertions, 5 deletions

diff --git a/drivers/usb/net/pegasus.c b/drivers/usb/net/pegasus.c
index d48c024cff59..6d12961cf9f9 100644
--- a/drivers/usb/net/pegasus.c
+++ b/drivers/usb/net/pegasus.c
@@ -316,6 +316,7 @@ static int update_eth_regs_async(pegasus_t * pegasus)
         return ret;
 }
 
+/* Returns 0 on success, error on failure */
 static int read_mii_word(pegasus_t * pegasus, __u8 phy, __u8 indx, __u16 * regd)
 {
         int i;
@@ -847,10 +848,16 @@ static void intr_callback(struct urb *urb)
                  * d[0].NO_CARRIER kicks in only with failed TX.
                  * ... so monitoring with MII may be safest.
                  */
-                if (d[0] & NO_CARRIER)
-                        netif_carrier_off(net); 
-                else
-                        netif_carrier_on(net);
+                if (pegasus->features & TRUST_LINK_STATUS) {
+                        if (d[5] & LINK_STATUS)
+                                netif_carrier_on(net);
+                        else
+                                netif_carrier_off(net);
+                } else {
+                        /* Never set carrier _on_ based on ! NO_CARRIER */
+                        if (d[0] & NO_CARRIER)
+                                netif_carrier_off(net); 
+                }
 
                 /* bytes 3-4 == rx_lostpkt, reg 2E/2F */
                 pegasus->stats.rx_missed_errors += ((d[3] & 0x7f) << 8) | d[4];
@@ -950,7 +957,7 @@ static void set_carrier(struct net_device *net)
         pegasus_t *pegasus = netdev_priv(net);
         u16 tmp;
 
-        if (!read_mii_word(pegasus, pegasus->phy, MII_BMSR, &tmp))
+        if (read_mii_word(pegasus, pegasus->phy, MII_BMSR, &tmp))
                 return;
 
         if (tmp & BMSR_LSTATUS)