[PATCH net-next v2] net: mscc: allow extracting the FCS into the skb

[Antoine Tenart]

This patch adds support for the NETIF_F_RXFCS feature in the Mscc
Ethernet driver. This feature is disabled by default and allow a user
to request the driver not to drop the FCS and to extract it into the skb
for debugging purposes.

Signed-off-by: Antoine Tenart <antoine.ten...@bootlin.com>
Reviewed-by: Alexandre Belloni <alexandre.bell...@bootlin.com>
---

Since v1:
  - Rebased on top of the latest net-next.

 drivers/net/ethernet/mscc/ocelot.c       | 2 +-
 drivers/net/ethernet/mscc/ocelot_board.c | 7 ++++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mscc/ocelot.c 
b/drivers/net/ethernet/mscc/ocelot.c
index 8f11fdba8d0e..9b8a17ee3cb3 100644
--- a/drivers/net/ethernet/mscc/ocelot.c
+++ b/drivers/net/ethernet/mscc/ocelot.c
@@ -1620,7 +1620,7 @@ int ocelot_probe_port(struct ocelot *ocelot, u8 port,
        dev->ethtool_ops = &ocelot_ethtool_ops;
        dev->switchdev_ops = &ocelot_port_switchdev_ops;
 
-       dev->hw_features |= NETIF_F_HW_VLAN_CTAG_FILTER;
+       dev->hw_features |= NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_RXFCS;
        dev->features |= NETIF_F_HW_VLAN_CTAG_FILTER;
 
        memcpy(dev->dev_addr, ocelot->base_mac, ETH_ALEN);
diff --git a/drivers/net/ethernet/mscc/ocelot_board.c 
b/drivers/net/ethernet/mscc/ocelot_board.c
index 0cf0b0935b3b..4c23d18bbf44 100644
--- a/drivers/net/ethernet/mscc/ocelot_board.c
+++ b/drivers/net/ethernet/mscc/ocelot_board.c
@@ -128,11 +128,16 @@ static irqreturn_t ocelot_xtr_irq_handler(int irq, void 
*arg)
                        len += sz;
                } while (len < buf_len);
 
-               /* Read the FCS and discard it */
+               /* Read the FCS */
                sz = ocelot_rx_frame_word(ocelot, grp, false, &val);
                /* Update the statistics if part of the FCS was read before */
                len -= ETH_FCS_LEN - sz;
 
+               if (unlikely(dev->features & NETIF_F_RXFCS)) {
+                       buf = (u32 *)skb_put(skb, ETH_FCS_LEN);
+                       *buf = val;
+               }
+
                if (sz < 0) {
                        err = sz;
                        break;
-- 
2.17.1