gianfar: Implement workaround for eTSEC74 erratum

MPC8313ECE says:

"If MACCFG2[Huge Frame]=0 and the Ethernet controller receives frames
 which are larger than MAXFRM, the controller truncates the frames to
 length MAXFRM and marks RxBD[TR]=1 to indicate the error. The controller
 also erroneously marks RxBD[TR]=1 if the received frame length is MAXFRM
 or MAXFRM-1, even though those frames are not truncated.
 No truncation or truncation error occurs if MACCFG2[Huge Frame]=1."

There are two options to workaround the issue:

"1. Set MACCFG2[Huge Frame]=1, so no truncation occurs for invalid large
 frames. Software can determine if a frame is larger than MAXFRM by
 reading RxBD[LG] or RxBD[Data Length].

 2. Set MAXFRM to 1538 (0x602) instead of the default 1536 (0x600), so
 normal-length frames are not marked as truncated. Software can examine
 RxBD[Data Length] to determine if the frame was larger than MAXFRM-2."

This patch implements the first workaround option by setting HUGEFRAME
bit, and gfar_clean_rx_ring() already checks the RxBD[Data Length].

Signed-off-by: Anton Vorontsov <avorontsov@mvista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/net/gianfar.h b/drivers/net/gianfar.h
index ac4a92e08c0..0a0483ce21d 100644
--- a/drivers/net/gianfar.h
+++ b/drivers/net/gianfar.h
@@ -1025,6 +1025,10 @@ struct gfar_priv_grp {
 	char int_name_er[GFAR_INT_NAME_MAX];
 };
 
+enum gfar_errata {
+	GFAR_ERRATA_74		= 0x01,
+};
+
 /* Struct stolen almost completely (and shamelessly) from the FCC enet source
  * (Ok, that's not so true anymore, but there is a family resemblence)
  * The GFAR buffer descriptors track the ring buffers.  The rx_bd_base
@@ -1049,6 +1053,7 @@ struct gfar_private {
 	struct device_node *node;
 	struct net_device *ndev;
 	struct of_device *ofdev;
+	enum gfar_errata errata;
 
 	struct gfar_priv_grp gfargrp[MAXGROUPS];
 	struct gfar_priv_tx_q *tx_queue[MAX_TX_QS];
@@ -1111,6 +1116,12 @@ struct gfar_private {
 extern unsigned int ftp_rqfpr[MAX_FILER_IDX + 1];
 extern unsigned int ftp_rqfcr[MAX_FILER_IDX + 1];
 
+static inline int gfar_has_errata(struct gfar_private *priv,
+				  enum gfar_errata err)
+{
+	return priv->errata & err;
+}
+
 static inline u32 gfar_read(volatile unsigned __iomem *addr)
 {
 	u32 val;