net: ftmac100: prepare data path for receiving single segment packets > 1514

Eliminate one check in the data path and move it elsewhere, to where our
real limitation is. We'll want to start processing "too long" frames in
the driver (currently there is a hardware MAC setting which drops
theses).

Signed-off-by: Vladimir Oltean <[e-mail]>
Signed-off-by: Sergei Antonov <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/ethernet/faraday/ftmac100.c

···
 	return rxdes->rxdes0 & cpu_to_le32(FTMAC100_RXDES0_CRC_ERR);
 }
 
-static bool ftmac100_rxdes_frame_too_long(struct ftmac100_rxdes *rxdes)
-{
-	return rxdes->rxdes0 & cpu_to_le32(FTMAC100_RXDES0_FTL);
-}
-
 static bool ftmac100_rxdes_runt(struct ftmac100_rxdes *rxdes)
 {
 	return rxdes->rxdes0 & cpu_to_le32(FTMAC100_RXDES0_RUNT);
···
 		error = true;
 	}
 
-	if (unlikely(ftmac100_rxdes_frame_too_long(rxdes))) {
-		if (net_ratelimit())
-			netdev_info(netdev, "rx frame too long\n");
-
-		netdev->stats.rx_length_errors++;
-		error = true;
-	} else if (unlikely(ftmac100_rxdes_runt(rxdes))) {
+	if (unlikely(ftmac100_rxdes_runt(rxdes))) {
 		if (net_ratelimit())
 			netdev_info(netdev, "rx runt\n");
 
···
 		netdev->stats.rx_length_errors++;
 		error = true;
 	}
+	/*
+	 * FTMAC100_RXDES0_FTL is not an error, it just indicates that the
+	 * frame is longer than 1518 octets. Receiving these is possible when
+	 * we told the hardware not to drop them, via FTMAC100_MACCR_RX_FTL.
+	 */
 
 	return error;
 }
···
 		return true;
 	}
 
-	/*
-	 * It is impossible to get multi-segment packets
-	 * because we always provide big enough receive buffers.
-	 */
+	/* We don't support multi-segment packets for now, so drop them. */
 	ret = ftmac100_rxdes_last_segment(rxdes);
-	BUG_ON(!ret);
+	if (unlikely(!ret)) {
+		netdev->stats.rx_length_errors++;
+		ftmac100_rx_drop_packet(priv);
+		return true;
+	}
 
 	/* start processing */
 	skb = netdev_alloc_skb_ip_align(netdev, 128);