e1000: omit stats for broken counter in 82543

The 82543 chip does not count tx_carrier_errors properly in FD mode;
report zeros instead of garbage.

Originally from Jesse Brandeburg <jesse.brandeburg@intel.com>, rewritten
to use feature flags by me.
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/net/e1000/e1000_hw.c

@@ -442,6 +442,12 @@ e1000_set_mac_type(struct e1000_hw *hw)
 		break;
 	}
 
+	/* The 82543 chip does not count tx_carrier_errors properly in
+	 * FD mode
+	 */
+	if (hw->mac_type == e1000_82543)
+		hw->bad_tx_carr_stats_fd = TRUE;
+
 	return E1000_SUCCESS;
 }
 

drivers/net/e1000/e1000_hw.h

@@ -1460,6 +1460,7 @@ struct e1000_hw {
 	boolean_t		mng_reg_access_disabled;
 	boolean_t		leave_av_bit_off;
 	boolean_t		kmrn_lock_loss_workaround_disabled;
+	boolean_t		bad_tx_carr_stats_fd;
 };
 
 

drivers/net/e1000/e1000_main.c

@@ -3581,6 +3581,11 @@ e1000_update_stats(struct e1000_adapter *adapter)
 	adapter->net_stats.tx_aborted_errors = adapter->stats.ecol;
 	adapter->net_stats.tx_window_errors = adapter->stats.latecol;
 	adapter->net_stats.tx_carrier_errors = adapter->stats.tncrs;
+	if (adapter->hw.bad_tx_carr_stats_fd &&
+	    adapter->link_duplex == FULL_DUPLEX) {
+		adapter->net_stats.tx_carrier_errors = 0;
+		adapter->stats.tncrs = 0;
+	}
 
 	/* Tx Dropped needs to be maintained elsewhere */