From f5b720b85944413491df106f05a784cd1714436e Mon Sep 17 00:00:00 2001 From: Claudiu Manoil Date: Wed, 15 Oct 2014 19:11:46 +0300 Subject: [PATCH] gianfar: Add FCS to rx buffer size (fix) For each Rx frame the eTSEC writes its FCS (Frame Check Sequence) to the Rx buffer. The eTSEC h/w manual states in the "Receive Buffer Descriptor Field Descriptions" table: "Data length is the number of octets written by the eTSEC into this BD's data buffer if L is cleared (the value is equal to MRBLR), or, if L is set, the length of the frame including *CRC*, FCB (if RCTRL[PRSDEP > 00), preamble (if MACCFG2[PreAmRxEn]=1), time stamp (if RCTRL[TS] = 1) and any padding (RCTRL[PAL])." Though the FCS bytes are removed by the driver before passing the skb to the net stack, the Rx buffer size computation does not currently take into account the FCS bytes (4 bytes). Because the Rx buffer size is multiple of 512 bytes, leaving out the FCS is not a problem for the default MTU of 1500, as the Rx buffer size is 1536 in this case. However, for custom MTUs, where the difference between the MTU size and the Rx buffer size is less, this can be a problem as the computed Rx buffer size won't be enough to accomodate the FCS for a received frame that is big enough (close to MTU size). In such case the received frame is considered to be incomplete (L flag not set in the RxBD status) and silently dropped. Note that the driver does not currently support S/G on Rx, so it has to compute its Rx buffer size based on the MTU of the device. Reported-by: Kristian Otnes Signed-off-by: Claudiu Manoil Signed-off-by: David S. Miller --- drivers/net/ethernet/freescale/gianfar.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c index 379b1a578d3d..4fdf0aa16978 100644 --- a/drivers/net/ethernet/freescale/gianfar.c +++ b/drivers/net/ethernet/freescale/gianfar.c @@ -338,7 +338,7 @@ static void gfar_init_tx_rx_base(struct gfar_private *priv) static void gfar_rx_buff_size_config(struct gfar_private *priv) { - int frame_size = priv->ndev->mtu + ETH_HLEN; + int frame_size = priv->ndev->mtu + ETH_HLEN + ETH_FCS_LEN; /* set this when rx hw offload (TOE) functions are being used */ priv->uses_rxfcb = 0; -- 2.20.1