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Subject[PATCH v2] LSO feature added to Cadence GEM driver
Date
New Cadence GEM hardware support Large Segment Offload (LSO):
TCP segmentation offload (TSO) as well as UDP fragmentation
offload (UFO). Support for those features was added to the driver.

Signed-off-by: Rafal Ozieblo <rafalo@cadence.com>
---
Changed in v2:
macb_lso_check_compatibility() changed to macb_features_check()
(with little modifications) and bind to .ndo_features_check.
(after Eric Dumazet suggestion)
---
drivers/net/ethernet/cadence/macb.c | 142 +++++++++++++++++++++++++++++++++---
drivers/net/ethernet/cadence/macb.h | 14 ++++
2 files changed, 144 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
index b32444a..30169fd 100644
--- a/drivers/net/ethernet/cadence/macb.c
+++ b/drivers/net/ethernet/cadence/macb.c
@@ -32,7 +32,9 @@
#include <linux/of_gpio.h>
#include <linux/of_mdio.h>
#include <linux/of_net.h>
-
+#include <linux/ip.h>
+#include <linux/udp.h>
+#include <linux/tcp.h>
#include "macb.h"

#define MACB_RX_BUFFER_SIZE 128
@@ -53,10 +55,13 @@
| MACB_BIT(TXERR))
#define MACB_TX_INT_FLAGS (MACB_TX_ERR_FLAGS | MACB_BIT(TCOMP))

-#define MACB_MAX_TX_LEN ((unsigned int)((1 << MACB_TX_FRMLEN_SIZE) - 1))
-#define GEM_MAX_TX_LEN ((unsigned int)((1 << GEM_TX_FRMLEN_SIZE) - 1))
+/* Max length of transmit frame must be a multiple of 8 bytes */
+#define MACB_TX_LEN_ALIGN 8
+#define MACB_MAX_TX_LEN ((unsigned int)((1 << MACB_TX_FRMLEN_SIZE) - 1) & ~((unsigned int)(MACB_TX_LEN_ALIGN - 1)))
+#define GEM_MAX_TX_LEN ((unsigned int)((1 << GEM_TX_FRMLEN_SIZE) - 1) & ~((unsigned int)(MACB_TX_LEN_ALIGN - 1)))

#define GEM_MTU_MIN_SIZE 68
+#define MACB_NETIF_LSO (NETIF_F_TSO | NETIF_F_UFO)

#define MACB_WOL_HAS_MAGIC_PACKET (0x1 << 0)
#define MACB_WOL_ENABLED (0x1 << 1)
@@ -1212,7 +1217,8 @@ static void macb_poll_controller(struct net_device *dev)

static unsigned int macb_tx_map(struct macb *bp,
struct macb_queue *queue,
- struct sk_buff *skb)
+ struct sk_buff *skb,
+ unsigned int hdrlen)
{
dma_addr_t mapping;
unsigned int len, entry, i, tx_head = queue->tx_head;
@@ -1220,14 +1226,27 @@ static unsigned int macb_tx_map(struct macb *bp,
struct macb_dma_desc *desc;
unsigned int offset, size, count = 0;
unsigned int f, nr_frags = skb_shinfo(skb)->nr_frags;
- unsigned int eof = 1;
- u32 ctrl;
+ unsigned int eof = 1, mss_mfs = 0;
+ u32 ctrl, lso_ctrl = 0, seq_ctrl = 0;
+
+ /* LSO */
+ if (skb_shinfo(skb)->gso_size != 0) {
+ if (IPPROTO_UDP == (((struct iphdr *)skb_network_header(skb))->protocol))
+ /* UDP - UFO */
+ lso_ctrl = MACB_LSO_UFO_ENABLE;
+ else
+ /* TCP - TSO */
+ lso_ctrl = MACB_LSO_TSO_ENABLE;
+ }

/* First, map non-paged data */
len = skb_headlen(skb);
+
+ /* first buffer length */
+ size = hdrlen;
+
offset = 0;
while (len) {
- size = min(len, bp->max_tx_length);
entry = macb_tx_ring_wrap(tx_head);
tx_skb = &queue->tx_skb[entry];

@@ -1247,6 +1266,8 @@ static unsigned int macb_tx_map(struct macb *bp,
offset += size;
count++;
tx_head++;
+
+ size = min(len, bp->max_tx_length);
}

/* Then, map paged data from fragments */
@@ -1300,6 +1321,20 @@ static unsigned int macb_tx_map(struct macb *bp,
desc = &queue->tx_ring[entry];
desc->ctrl = ctrl;

+ if (lso_ctrl) {
+ if (lso_ctrl == MACB_LSO_UFO_ENABLE)
+ /* include header and FCS in value given to h/w */
+ mss_mfs = skb_shinfo(skb)->gso_size +
+ skb_transport_offset(skb) + 4;
+ else /* TSO */ {
+ mss_mfs = skb_shinfo(skb)->gso_size;
+ /* TCP Sequence Number Source Select
+ * can be set only for TSO
+ */
+ seq_ctrl = 0;
+ }
+ }
+
do {
i--;
entry = macb_tx_ring_wrap(i);
@@ -1314,6 +1349,16 @@ static unsigned int macb_tx_map(struct macb *bp,
if (unlikely(entry == (TX_RING_SIZE - 1)))
ctrl |= MACB_BIT(TX_WRAP);

+ /* First descriptor is header descriptor */
+ if (i == queue->tx_head) {
+ ctrl |= MACB_BF(TX_LSO, lso_ctrl);
+ ctrl |= MACB_BF(TX_TCP_SEQ_SRC, seq_ctrl);
+ } else
+ /* Only set MSS/MFS on payload descriptors
+ * (second or later descriptor)
+ */
+ ctrl |= MACB_BF(MSS_MFS, mss_mfs);
+
/* Set TX buffer descriptor */
macb_set_addr(desc, tx_skb->mapping);
/* desc->addr must be visible to hardware before clearing
@@ -1339,6 +1384,43 @@ static unsigned int macb_tx_map(struct macb *bp,
return 0;
}

+static netdev_features_t macb_features_check(struct sk_buff *skb,
+ struct net_device *dev,
+ netdev_features_t features)
+{
+ unsigned int nr_frags, f;
+ unsigned int hdrlen;
+
+ /* Validate LSO compatibility */
+
+ /* there is only one buffer */
+ if (!skb_is_nonlinear(skb))
+ return features;
+
+ /* length of header */
+ hdrlen = skb_transport_offset(skb);
+ if (IPPROTO_TCP == (((struct iphdr *)skb_network_header(skb))->protocol))
+ hdrlen += tcp_hdrlen(skb);
+
+ /* For LSO:
+ * When software supplies two or more payload buffers all payload buffers
+ * apart from the last must be a multiple of 8 bytes in size.
+ */
+ if (!IS_ALIGNED(skb_headlen(skb) - hdrlen, MACB_TX_LEN_ALIGN))
+ return features & ~MACB_NETIF_LSO;
+
+ nr_frags = skb_shinfo(skb)->nr_frags;
+ /* No need to check last fragment */
+ nr_frags--;
+ for (f = 0; f < nr_frags; f++) {
+ const skb_frag_t *frag = &skb_shinfo(skb)->frags[f];
+
+ if (!IS_ALIGNED(skb_frag_size(frag), MACB_TX_LEN_ALIGN))
+ return features & ~MACB_NETIF_LSO;
+ }
+ return features;
+}
+
static inline int macb_clear_csum(struct sk_buff *skb)
{
/* no change for packets without checksum offloading */
@@ -1363,7 +1445,27 @@ static int macb_start_xmit(struct sk_buff *skb, struct net_device *dev)
struct macb *bp = netdev_priv(dev);
struct macb_queue *queue = &bp->queues[queue_index];
unsigned long flags;
- unsigned int count, nr_frags, frag_size, f;
+ unsigned int desc_cnt, nr_frags, frag_size, f;
+ unsigned int is_lso = 0, is_udp, hdrlen;
+
+ is_lso = (skb_shinfo(skb)->gso_size != 0);
+
+ if (is_lso) {
+ is_udp = (IPPROTO_UDP == (((struct iphdr *)skb_network_header(skb))->protocol));
+
+ /* length of headers */
+ if (is_udp)
+ /* only queue eth + ip headers separately for UDP */
+ hdrlen = skb_transport_offset(skb);
+ else
+ hdrlen = skb_transport_offset(skb) + tcp_hdrlen(skb);
+ if (skb_headlen(skb) < hdrlen) {
+ netdev_err(bp->dev, "Error - LSO headers fragmented!!!\n");
+ /* if this is required, would need to copy to single buffer */
+ return NETDEV_TX_BUSY;
+ }
+ } else
+ hdrlen = min(skb_headlen(skb), bp->max_tx_length);

#if defined(DEBUG) && defined(VERBOSE_DEBUG)
netdev_vdbg(bp->dev,
@@ -1378,17 +1480,21 @@ static int macb_start_xmit(struct sk_buff *skb, struct net_device *dev)
* socket buffer: skb fragments of jumbo frames may need to be
* split into many buffer descriptors.
*/
- count = DIV_ROUND_UP(skb_headlen(skb), bp->max_tx_length);
+ if (is_lso && (skb_headlen(skb) > hdrlen))
+ /* extra header descriptor if also payload in first buffer */
+ desc_cnt = DIV_ROUND_UP((skb_headlen(skb) - hdrlen), bp->max_tx_length) + 1;
+ else
+ desc_cnt = DIV_ROUND_UP(skb_headlen(skb), bp->max_tx_length);
nr_frags = skb_shinfo(skb)->nr_frags;
for (f = 0; f < nr_frags; f++) {
frag_size = skb_frag_size(&skb_shinfo(skb)->frags[f]);
- count += DIV_ROUND_UP(frag_size, bp->max_tx_length);
+ desc_cnt += DIV_ROUND_UP(frag_size, bp->max_tx_length);
}

spin_lock_irqsave(&bp->lock, flags);

/* This is a hard error, log it. */
- if (CIRC_SPACE(queue->tx_head, queue->tx_tail, TX_RING_SIZE) < count) {
+ if (CIRC_SPACE(queue->tx_head, queue->tx_tail, TX_RING_SIZE) < desc_cnt) {
netif_stop_subqueue(dev, queue_index);
spin_unlock_irqrestore(&bp->lock, flags);
netdev_dbg(bp->dev, "tx_head = %u, tx_tail = %u\n",
@@ -1396,13 +1502,19 @@ static int macb_start_xmit(struct sk_buff *skb, struct net_device *dev)
return NETDEV_TX_BUSY;
}

+ if (is_lso) {
+ if (is_udp)
+ /* zero UDP checksum, not calculated by h/w for UFO */
+ udp_hdr(skb)->check = 0;
+ }
+
if (macb_clear_csum(skb)) {
dev_kfree_skb_any(skb);
goto unlock;
}

/* Map socket buffer for DMA transfer */
- if (!macb_tx_map(bp, queue, skb)) {
+ if (!macb_tx_map(bp, queue, skb, hdrlen)) {
dev_kfree_skb_any(skb);
goto unlock;
}
@@ -2298,6 +2410,7 @@ static const struct net_device_ops macb_netdev_ops = {
.ndo_poll_controller = macb_poll_controller,
#endif
.ndo_set_features = macb_set_features,
+ .ndo_features_check = macb_features_check,
};

/* Configure peripheral capabilities according to device tree
@@ -2501,6 +2614,11 @@ static int macb_init(struct platform_device *pdev)

/* Set features */
dev->hw_features = NETIF_F_SG;
+
+ /* Check LSO capability */
+ if (GEM_BFEXT(PBUF_LSO, gem_readl(bp, DCFG6)))
+ dev->hw_features |= MACB_NETIF_LSO;
+
/* Checksum offload is only available on gem with packet buffer */
if (macb_is_gem(bp) && !(bp->caps & MACB_CAPS_FIFO_MODE))
dev->hw_features |= NETIF_F_HW_CSUM | NETIF_F_RXCSUM;
diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
index 8bed4b5..534aded 100644
--- a/drivers/net/ethernet/cadence/macb.h
+++ b/drivers/net/ethernet/cadence/macb.h
@@ -382,6 +382,10 @@
#define GEM_TX_PKT_BUFF_OFFSET 21
#define GEM_TX_PKT_BUFF_SIZE 1

+/* Bitfields in DCFG6. */
+#define GEM_PBUF_LSO_OFFSET 27
+#define GEM_PBUF_LSO_SIZE 1
+
/* Constants for CLK */
#define MACB_CLK_DIV8 0
#define MACB_CLK_DIV16 1
@@ -414,6 +418,10 @@
#define MACB_CAPS_SG_DISABLED 0x40000000
#define MACB_CAPS_MACB_IS_GEM 0x80000000

+/* LSO settings */
+#define MACB_LSO_UFO_ENABLE 0x01
+#define MACB_LSO_TSO_ENABLE 0x02
+
/* Bit manipulation macros */
#define MACB_BIT(name) \
(1 << MACB_##name##_OFFSET)
@@ -545,6 +553,12 @@ struct macb_dma_desc {
#define MACB_TX_LAST_SIZE 1
#define MACB_TX_NOCRC_OFFSET 16
#define MACB_TX_NOCRC_SIZE 1
+#define MACB_MSS_MFS_OFFSET 16
+#define MACB_MSS_MFS_SIZE 14
+#define MACB_TX_LSO_OFFSET 17
+#define MACB_TX_LSO_SIZE 2
+#define MACB_TX_TCP_SEQ_SRC_OFFSET 19
+#define MACB_TX_TCP_SEQ_SRC_SIZE 1
#define MACB_TX_BUF_EXHAUSTED_OFFSET 27
#define MACB_TX_BUF_EXHAUSTED_SIZE 1
#define MACB_TX_UNDERRUN_OFFSET 28
--
2.4.5
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