Commit ba779711 authored by Claudiu Manoil's avatar Claudiu Manoil Committed by David S. Miller
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gianfar: Fix and cleanup Rx FCB indication

This fixes a less obvious error on one hand, and prevents futher
similar errors by disambiguating and optimizing RxFCB indication,
on the other hand.

The error consists in NETIF_F_HW_VLAN_TX flag being used as an
indication of Rx FCB insertion. This happened as soon gfar_uses_fcb(),
which despite its name indicates Rx FCB insertion, started
incorporating is_vlan_on().
is_vlan_on(), on the other hand, is also a misleading construct because
we need to differentiate b/w hw VLAN extraction/VLEX (marked by VLAN_RX
flag) and hw VLAN insertion/VLINS (VLAN_TX flag), which are different
mechanisms using different types of FCBs.

The hw spec for the RxFCB feature is as follows:
In the case of RxBD rings, FCBs (Frame Control Block) are inserted by
the eTSEC whenever RCTRL[PRSDEP] is set to a non-zero value. Only one
FCB is inserted per frame (in the buffer pointed to by the RxBD with
bit F set). TOE acceleration for receive is enabled for all rx frames
in this case.

This patch introduces priv->uses_rxfcb field to quickly signal RxFCB
insertion in accordance with the specification above.

The dependency on FSL_GIANFAR_DEV_HAS_TIMER was also eliminated as
another source of confusion. The actual dependency is to priv->hwts_rx_en.
Upon changing priv->hwts_rx_en via IOCTL, the gfar device is being
restarted and on init_mac() the priv->hwts_rx_en flag determines RxFCB
insertion, and rctrl is programmed accordingly. The patch takes care
of this case too.

Though maybe not as self documenting as the inlining version uses_fcb(),
priv->uses_rxfcb has the main purpose to quickly signal, on the hot path,
that the incoming frame has a *Rx* FCB block inserted which needs to be
pulled out before passing the skb to the stack. This is a performance
critical operation, it needs to happen fast, that's why uses_rxfcb is
placed in the first cacheline of gfar_private.
This is also why a cached rctrl cannot be used instead: 1) because
we don't have 32 bits available in the first cacheline of gfar_priv
(but only 16); 2) bit operations are expensive on the hot path.
Signed-off-by: default avatarClaudiu Manoil <>
Signed-off-by: default avatarDavid S. Miller <>
parent 13f228da
......@@ -344,6 +344,9 @@ static void gfar_init_mac(struct net_device *ndev)
/* Configure the coalescing support */
gfar_configure_coalescing(priv, 0xFF, 0xFF);
/* set this when rx hw offload (TOE) functions are being used */
priv->uses_rxfcb = 0;
if (priv->rx_filer_enable) {
rctrl |= RCTRL_FILREN;
/* Program the RIR0 reg with the required distribution */
......@@ -354,8 +357,10 @@ static void gfar_init_mac(struct net_device *ndev)
if (ndev->flags & IFF_PROMISC)
rctrl |= RCTRL_PROM;
if (ndev->features & NETIF_F_RXCSUM)
if (ndev->features & NETIF_F_RXCSUM) {
priv->uses_rxfcb = 1;
if (priv->extended_hash) {
......@@ -377,11 +382,15 @@ static void gfar_init_mac(struct net_device *ndev)
/* Enable HW time stamping if requested from user space */
if (priv->hwts_rx_en)
if (priv->hwts_rx_en) {
priv->uses_rxfcb = 1;
if (ndev->features & NETIF_F_HW_VLAN_RX)
if (ndev->features & NETIF_F_HW_VLAN_RX) {
priv->uses_rxfcb = 1;
/* Init rctrl based on our settings */
gfar_write(&regs->rctrl, rctrl);
......@@ -500,20 +509,6 @@ void unlock_tx_qs(struct gfar_private *priv)
static bool gfar_is_vlan_on(struct gfar_private *priv)
return (priv->ndev->features & NETIF_F_HW_VLAN_RX) ||
(priv->ndev->features & NETIF_F_HW_VLAN_TX);
/* Returns 1 if incoming frames use an FCB */
static inline int gfar_uses_fcb(struct gfar_private *priv)
return gfar_is_vlan_on(priv) ||
(priv->ndev->features & NETIF_F_RXCSUM) ||
(priv->device_flags & FSL_GIANFAR_DEV_HAS_TIMER);
static void free_tx_pointers(struct gfar_private *priv)
int i;
......@@ -2326,10 +2321,13 @@ void gfar_check_rx_parser_mode(struct gfar_private *priv)
tempval = gfar_read(&regs->rctrl);
/* If parse is no longer required, then disable parser */
if (tempval & RCTRL_REQ_PARSER)
if (tempval & RCTRL_REQ_PARSER) {
priv->uses_rxfcb = 1;
} else {
tempval &= ~RCTRL_PRSDEP_INIT;
priv->uses_rxfcb = 0;
gfar_write(&regs->rctrl, tempval);
......@@ -2362,6 +2360,7 @@ void gfar_vlan_mode(struct net_device *dev, netdev_features_t features)
tempval = gfar_read(&regs->rctrl);
gfar_write(&regs->rctrl, tempval);
priv->uses_rxfcb = 1;
} else {
/* Disable VLAN tag extraction */
tempval = gfar_read(&regs->rctrl);
......@@ -2390,7 +2389,7 @@ static int gfar_change_mtu(struct net_device *dev, int new_mtu)
return -EINVAL;
if (gfar_uses_fcb(priv))
if (priv->uses_rxfcb)
frame_size += GMAC_FCB_LEN;
frame_size += priv->padding;
......@@ -2759,7 +2758,7 @@ int gfar_clean_rx_ring(struct gfar_priv_rx_q *rx_queue, int rx_work_limit)
bdp = rx_queue->cur_rx;
base = rx_queue->rx_bd_base;
amount_pull = (gfar_uses_fcb(priv) ? GMAC_FCB_LEN : 0);
amount_pull = priv->uses_rxfcb ? GMAC_FCB_LEN : 0;
while (!((bdp->status & RXBD_EMPTY) || (--rx_work_limit < 0))) {
struct sk_buff *newskb;
......@@ -1056,6 +1056,7 @@ struct gfar_private {
enum gfar_errata errata;
unsigned int rx_buffer_size;
u16 uses_rxfcb;
u16 padding;
/* HW time stamping enabled flag */
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