net: fec: Add software TSO support

Add software TSO support for FEC.
This feature allows to improve outbound throughput performance.

Tested on imx6dl sabresd board, running iperf tcp tests shows:
- 16.2% improvement comparing with FEC SG patch
- 82% improvement comparing with NO SG & TSO patch

$ ethtool -K eth0 tso on
$ iperf -c 10.192.242.167 -t 3 &
[  3] local 10.192.242.108 port 35388 connected with 10.192.242.167 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0- 3.0 sec   181 MBytes   506 Mbits/sec

During the testing, CPU loading is 30%.
Since imx6dl FEC Bandwidth is limited to SOC system bus bandwidth, the
performance with SW TSO is a milestone.

CC: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: David Laight <David.Laight@ACULAB.COM>
CC: Li Frank <B20596@freescale.com>
Signed-off-by: Fugang Duan <B38611@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 238 insertions, 23 deletions

diff --git a/drivers/net/ethernet/freescale/fec.h b/drivers/net/ethernet/freescale/fec.h
index e7ce14d8d3c3..671d080105a7 100644
--- a/drivers/net/ethernet/freescale/fec.h
+++ b/drivers/net/ethernet/freescale/fec.h
@@ -299,6 +299,12 @@ struct fec_enet_private {
         unsigned short bufdesc_size;
         unsigned short tx_ring_size;
         unsigned short rx_ring_size;
+        unsigned short tx_stop_threshold;
+        unsigned short tx_wake_threshold;
+
+        /* Software TSO */
+        char *tso_hdrs;
+        dma_addr_t tso_hdrs_dma;
 
         struct  platform_device *pdev;
 
diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index bea00a8d6c99..38d9d276ab8b 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -36,6 +36,7 @@
 #include <linux/in.h>
 #include <linux/ip.h>
 #include <net/ip.h>
+#include <net/tso.h>
 #include <linux/tcp.h>
 #include <linux/udp.h>
 #include <linux/icmp.h>
@@ -228,6 +229,15 @@ MODULE_PARM_DESC(macaddr, "FEC Ethernet MAC address");
 #define FEC_PAUSE_FLAG_AUTONEG  0x1
 #define FEC_PAUSE_FLAG_ENABLE   0x2
 
+#define TSO_HEADER_SIZE         128
+/* Max number of allowed TCP segments for software TSO */
+#define FEC_MAX_TSO_SEGS        100
+#define FEC_MAX_SKB_DESCS       (FEC_MAX_TSO_SEGS * 2 + MAX_SKB_FRAGS)
+
+#define IS_TSO_HEADER(txq, addr) \
+        ((addr >= txq->tso_hdrs_dma) && \
+        (addr < txq->tso_hdrs_dma + txq->tx_ring_size * TSO_HEADER_SIZE))
+
 static int mii_cnt;
 
 static inline
@@ -438,8 +448,17 @@ static int fec_enet_txq_submit_skb(struct sk_buff *skb, struct net_device *ndev)
         unsigned short buflen;
         unsigned int estatus = 0;
         unsigned int index;
+        int entries_free;
         int ret;
 
+        entries_free = fec_enet_get_free_txdesc_num(fep);
+        if (entries_free < MAX_SKB_FRAGS + 1) {
+                dev_kfree_skb_any(skb);
+                if (net_ratelimit())
+                        netdev_err(ndev, "NOT enough BD for SG!\n");
+                return NETDEV_TX_OK;
+        }
+
         /* Protocol checksum off-load for TCP and UDP. */
         if (fec_enet_clear_csum(skb, ndev)) {
                 dev_kfree_skb_any(skb);
@@ -534,35 +553,210 @@ static int fec_enet_txq_submit_skb(struct sk_buff *skb, struct net_device *ndev)
         return 0;
 }
 
-static netdev_tx_t
-fec_enet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
+static int
+fec_enet_txq_put_data_tso(struct sk_buff *skb, struct net_device *ndev,
+                        struct bufdesc *bdp, int index, char *data,
+                        int size, bool last_tcp, bool is_last)
 {
         struct fec_enet_private *fep = netdev_priv(ndev);
-        struct bufdesc *bdp;
-        unsigned short  status;
-        int entries_free;
-        int ret;
-
-        /* Fill in a Tx ring entry */
-        bdp = fep->cur_tx;
+        const struct platform_device_id *id_entry =
+                                platform_get_device_id(fep->pdev);
+        struct bufdesc_ex *ebdp = (struct bufdesc_ex *)bdp;
+        unsigned short status;
+        unsigned int estatus = 0;
 
         status = bdp->cbd_sc;
+        status &= ~BD_ENET_TX_STATS;
 
-        if (status & BD_ENET_TX_READY) {
-                /* Ooops.  All transmit buffers are full.  Bail out.
-                 * This should not happen, since ndev->tbusy should be set.
-                 */
+        status |= (BD_ENET_TX_TC | BD_ENET_TX_READY);
+        bdp->cbd_datlen = size;
+
+        if (((unsigned long) data) & FEC_ALIGNMENT ||
+                id_entry->driver_data & FEC_QUIRK_SWAP_FRAME) {
+                memcpy(fep->tx_bounce[index], data, size);
+                data = fep->tx_bounce[index];
+
+                if (id_entry->driver_data & FEC_QUIRK_SWAP_FRAME)
+                        swap_buffer(data, size);
+        }
+
+        bdp->cbd_bufaddr = dma_map_single(&fep->pdev->dev, data,
+                                        size, DMA_TO_DEVICE);
+        if (dma_mapping_error(&fep->pdev->dev, bdp->cbd_bufaddr)) {
+                dev_kfree_skb_any(skb);
                 if (net_ratelimit())
-                        netdev_err(ndev, "tx queue full!\n");
+                        netdev_err(ndev, "Tx DMA memory map failed\n");
                 return NETDEV_TX_BUSY;
         }
 
-        ret = fec_enet_txq_submit_skb(skb, ndev);
+        if (fep->bufdesc_ex) {
+                if (skb->ip_summed == CHECKSUM_PARTIAL)
+                        estatus |= BD_ENET_TX_PINS | BD_ENET_TX_IINS;
+                ebdp->cbd_bdu = 0;
+                ebdp->cbd_esc = estatus;
+        }
+
+        /* Handle the last BD specially */
+        if (last_tcp)
+                status |= (BD_ENET_TX_LAST | BD_ENET_TX_TC);
+        if (is_last) {
+                status |= BD_ENET_TX_INTR;
+                if (fep->bufdesc_ex)
+                        ebdp->cbd_esc |= BD_ENET_TX_INT;
+        }
+
+        bdp->cbd_sc = status;
+
+        return 0;
+}
+
+static int
+fec_enet_txq_put_hdr_tso(struct sk_buff *skb, struct net_device *ndev,
+                        struct bufdesc *bdp, int index)
+{
+        struct fec_enet_private *fep = netdev_priv(ndev);
+        const struct platform_device_id *id_entry =
+                                platform_get_device_id(fep->pdev);
+        int hdr_len = skb_transport_offset(skb) + tcp_hdrlen(skb);
+        struct bufdesc_ex *ebdp = (struct bufdesc_ex *)bdp;
+        void *bufaddr;
+        unsigned long dmabuf;
+        unsigned short status;
+        unsigned int estatus = 0;
+
+        status = bdp->cbd_sc;
+        status &= ~BD_ENET_TX_STATS;
+        status |= (BD_ENET_TX_TC | BD_ENET_TX_READY);
+
+        bufaddr = fep->tso_hdrs + index * TSO_HEADER_SIZE;
+        dmabuf = fep->tso_hdrs_dma + index * TSO_HEADER_SIZE;
+        if (((unsigned long) bufaddr) & FEC_ALIGNMENT ||
+                id_entry->driver_data & FEC_QUIRK_SWAP_FRAME) {
+                memcpy(fep->tx_bounce[index], skb->data, hdr_len);
+                bufaddr = fep->tx_bounce[index];
+
+                if (id_entry->driver_data & FEC_QUIRK_SWAP_FRAME)
+                        swap_buffer(bufaddr, hdr_len);
+
+                dmabuf = dma_map_single(&fep->pdev->dev, bufaddr,
+                                        hdr_len, DMA_TO_DEVICE);
+                if (dma_mapping_error(&fep->pdev->dev, dmabuf)) {
+                        dev_kfree_skb_any(skb);
+                        if (net_ratelimit())
+                                netdev_err(ndev, "Tx DMA memory map failed\n");
+                        return NETDEV_TX_BUSY;
+                }
+        }
+
+        bdp->cbd_bufaddr = dmabuf;
+        bdp->cbd_datlen = hdr_len;
+
+        if (fep->bufdesc_ex) {
+                if (skb->ip_summed == CHECKSUM_PARTIAL)
+                        estatus |= BD_ENET_TX_PINS | BD_ENET_TX_IINS;
+                ebdp->cbd_bdu = 0;
+                ebdp->cbd_esc = estatus;
+        }
+
+        bdp->cbd_sc = status;
+
+        return 0;
+}
+
+static int fec_enet_txq_submit_tso(struct sk_buff *skb, struct net_device *ndev)
+{
+        struct fec_enet_private *fep = netdev_priv(ndev);
+        int hdr_len = skb_transport_offset(skb) + tcp_hdrlen(skb);
+        int total_len, data_left;
+        struct bufdesc *bdp = fep->cur_tx;
+        struct tso_t tso;
+        unsigned int index = 0;
+        int ret;
+
+        if (tso_count_descs(skb) >= fec_enet_get_free_txdesc_num(fep)) {
+                dev_kfree_skb_any(skb);
+                if (net_ratelimit())
+                        netdev_err(ndev, "NOT enough BD for TSO!\n");
+                return NETDEV_TX_OK;
+        }
+
+        /* Protocol checksum off-load for TCP and UDP. */
+        if (fec_enet_clear_csum(skb, ndev)) {
+                dev_kfree_skb_any(skb);
+                return NETDEV_TX_OK;
+        }
+
+        /* Initialize the TSO handler, and prepare the first payload */
+        tso_start(skb, &tso);
+
+        total_len = skb->len - hdr_len;
+        while (total_len > 0) {
+                char *hdr;
+
+                index = fec_enet_get_bd_index(fep->tx_bd_base, bdp, fep);
+                data_left = min_t(int, skb_shinfo(skb)->gso_size, total_len);
+                total_len -= data_left;
+
+                /* prepare packet headers: MAC + IP + TCP */
+                hdr = fep->tso_hdrs + index * TSO_HEADER_SIZE;
+                tso_build_hdr(skb, hdr, &tso, data_left, total_len == 0);
+                ret = fec_enet_txq_put_hdr_tso(skb, ndev, bdp, index);
+                if (ret)
+                        goto err_release;
+
+                while (data_left > 0) {
+                        int size;
+
+                        size = min_t(int, tso.size, data_left);
+                        bdp = fec_enet_get_nextdesc(bdp, fep);
+                        index = fec_enet_get_bd_index(fep->tx_bd_base, bdp, fep);
+                        ret = fec_enet_txq_put_data_tso(skb, ndev, bdp, index, tso.data,
+                                                        size, size == data_left,
+                                                        total_len == 0);
+                        if (ret)
+                                goto err_release;
+
+                        data_left -= size;
+                        tso_build_data(skb, &tso, size);
+                }
+
+                bdp = fec_enet_get_nextdesc(bdp, fep);
+        }
+
+        /* Save skb pointer */
+        fep->tx_skbuff[index] = skb;
+
+        fec_enet_submit_work(bdp, fep);
+
+        skb_tx_timestamp(skb);
+        fep->cur_tx = bdp;
+
+        /* Trigger transmission start */
+        writel(0, fep->hwp + FEC_X_DES_ACTIVE);
+
+        return 0;
+
+err_release:
+        /* TODO: Release all used data descriptors for TSO */
+        return ret;
+}
+
+static netdev_tx_t
+fec_enet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
+{
+        struct fec_enet_private *fep = netdev_priv(ndev);
+        int entries_free;
+        int ret;
+
+        if (skb_is_gso(skb))
+                ret = fec_enet_txq_submit_tso(skb, ndev);
+        else
+                ret = fec_enet_txq_submit_skb(skb, ndev);
         if (ret)
                 return ret;
 
         entries_free = fec_enet_get_free_txdesc_num(fep);
-        if (entries_free < MAX_SKB_FRAGS + 1)
+        if (entries_free <= fep->tx_stop_threshold)
                 netif_stop_queue(ndev);
 
         return NETDEV_TX_OK;
@@ -883,7 +1077,7 @@ fec_enet_tx(struct net_device *ndev)
         unsigned short status;
         struct  sk_buff *skb;
         int     index = 0;
-        int     entries;
+        int     entries_free;
 
         fep = netdev_priv(ndev);
         bdp = fep->dirty_tx;
@@ -900,8 +1094,9 @@ fec_enet_tx(struct net_device *ndev)
                 index = fec_enet_get_bd_index(fep->tx_bd_base, bdp, fep);
 
                 skb = fep->tx_skbuff[index];
-                dma_unmap_single(&fep->pdev->dev, bdp->cbd_bufaddr, bdp->cbd_datlen,
-                                DMA_TO_DEVICE);
+                if (!IS_TSO_HEADER(fep, bdp->cbd_bufaddr))
+                        dma_unmap_single(&fep->pdev->dev, bdp->cbd_bufaddr,
+                                        bdp->cbd_datlen, DMA_TO_DEVICE);
                 bdp->cbd_bufaddr = 0;
                 if (!skb) {
                         bdp = fec_enet_get_nextdesc(bdp, fep);
@@ -962,9 +1157,11 @@ fec_enet_tx(struct net_device *ndev)
 
                 /* Since we have freed up a buffer, the ring is no longer full
                  */
-                entries = fec_enet_get_free_txdesc_num(fep);
-                if (entries >= MAX_SKB_FRAGS + 1 && netif_queue_stopped(ndev))
-                        netif_wake_queue(ndev);
+                if (netif_queue_stopped(ndev)) {
+                        entries_free = fec_enet_get_free_txdesc_num(fep);
+                        if (entries_free >= fep->tx_wake_threshold)
+                                netif_wake_queue(ndev);
+                }
         }
         return;
 }
@@ -2166,6 +2363,9 @@ static int fec_enet_init(struct net_device *ndev)
         fep->tx_ring_size = TX_RING_SIZE;
         fep->rx_ring_size = RX_RING_SIZE;
 
+        fep->tx_stop_threshold = FEC_MAX_SKB_DESCS;
+        fep->tx_wake_threshold = (fep->tx_ring_size - fep->tx_stop_threshold) / 2;
+
         if (fep->bufdesc_ex)
                 fep->bufdesc_size = sizeof(struct bufdesc_ex);
         else
@@ -2179,6 +2379,13 @@ static int fec_enet_init(struct net_device *ndev)
         if (!cbd_base)
                 return -ENOMEM;
 
+        fep->tso_hdrs = dma_alloc_coherent(NULL, fep->tx_ring_size * TSO_HEADER_SIZE,
+                                                &fep->tso_hdrs_dma, GFP_KERNEL);
+        if (!fep->tso_hdrs) {
+                dma_free_coherent(NULL, bd_size, cbd_base, fep->bd_dma);
+                return -ENOMEM;
+        }
+
         memset(cbd_base, 0, PAGE_SIZE);
 
         fep->netdev = ndev;
@@ -2209,9 +2416,11 @@ static int fec_enet_init(struct net_device *ndev)
                 ndev->features |= NETIF_F_HW_VLAN_CTAG_RX;
 
         if (id_entry->driver_data & FEC_QUIRK_HAS_CSUM) {
+                ndev->gso_max_segs = FEC_MAX_TSO_SEGS;
+
                 /* enable hw accelerator */
                 ndev->features |= (NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM
-                                | NETIF_F_RXCSUM | NETIF_F_SG);
+                                | NETIF_F_RXCSUM | NETIF_F_SG | NETIF_F_TSO);
                 fep->csum_flags |= FLAG_RX_CSUM_ENABLED;
         }