net: davinci_emac: Invalidate only the received portion of a buffer

ATM when receiving a packet the whole buffer is invalidated, this change
optimizes this behaviour.

Signed-off-by: Karl Beldan <karl.beldan+oss@gmail.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Mugunthan V N <mugunthanvnm@ti.com>

drivers/net/davinci_emac.c

@@ -681,12 +681,12 @@ static int davinci_eth_rcv_packet (struct eth_device *dev)
 			printf ("WARN: emac_rcv_pkt: Error in packet\n");
 		} else {
 			unsigned long tmp = (unsigned long)rx_curr_desc->buffer;
+			unsigned short len =
+				rx_curr_desc->buff_off_len & 0xffff;
 
-			invalidate_dcache_range(tmp, tmp + EMAC_RXBUF_SIZE);
-			net_process_received_packet(
-				rx_curr_desc->buffer,
-				rx_curr_desc->buff_off_len & 0xffff);
-			ret = rx_curr_desc->buff_off_len & 0xffff;
+			invalidate_dcache_range(tmp, tmp + ALIGN(len, PKTALIGN));
+			net_process_received_packet(rx_curr_desc->buffer, len);
+			ret = len;
 		}
 
 		/* Ack received packet descriptor */