net: fec: fix receive error handling

The FEC receive error handling suffers from several problems:
1. When a FIFO overrun error occurs, the descriptor is closed and
   reception stops.  The remainder of the packet is discarded by the
   MAC.

   The documentation states that other status bits are invalid, and they
   will be zero.  However, practical experience on iMX6 shows this is
   not the case - the CR (crc error) bit will also be set.

   This leads to each FIFO overrun event incrementing both the fifo
   error count and the crc error count, which makes the error statistics
   less useful.  Fix this by ignoring all other status bits of the FIFO
   overrun is set, and add a comment to that effect.

2. A late collision invalidates all but the overrun condition; the
   remaining error conditions must be ignored.

3. Despite accounting for errors, it continues to receive the errored
   packets and pass them into the network stack as if they were
   correctly received.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/net/ethernet/freescale/fec.h b/drivers/net/ethernet/freescale/fec.h
index ee41d98b44b6..ec4c76264eb9 100644
--- a/drivers/net/ethernet/freescale/fec.h
+++ b/drivers/net/ethernet/freescale/fec.h
@@ -202,6 +202,7 @@ struct bufdesc_ex {
 #define BD_ENET_RX_OV           ((ushort)0x0002)
 #define BD_ENET_RX_CL           ((ushort)0x0001)
 #define BD_ENET_RX_STATS        ((ushort)0x013f)        /* All status bits */
+#define BD_ENET_RX_ERROR	((ushort)0x003f)
 
 /* Enhanced buffer descriptor control/status used by Ethernet receive */
 #define BD_ENET_RX_VLAN         0x00000004