drivers: net: xgene: Fix MSS programming

Current driver programs static value of MSS in hardware register for TSO
offload engine to segment the TCP payload regardless the MSS value
provided by network stack.

This patch fixes this by programming hardware registers with the
stack provided MSS value.

Since the hardware has the limitation of having only 4 MSS registers,
this patch uses reference count of mss values being used.

Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
Signed-off-by: Toan Le <toanle@apm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 73 insertions, 17 deletions

diff --git a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
index 522ba920bfc1..429f18fc5503 100644
--- a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
+++ b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
@@ -137,6 +137,7 @@ static irqreturn_t xgene_enet_rx_irq(const int irq, void *data)
 static int xgene_enet_tx_completion(struct xgene_enet_desc_ring *cp_ring,
 				    struct xgene_enet_raw_desc *raw_desc)
 {
+	struct xgene_enet_pdata *pdata = netdev_priv(cp_ring->ndev);
 	struct sk_buff *skb;
 	struct device *dev;
 	skb_frag_t *frag;
@@ -144,6 +145,7 @@ static int xgene_enet_tx_completion(struct xgene_enet_desc_ring *cp_ring,
 	u16 skb_index;
 	u8 status;
 	int i, ret = 0;
+	u8 mss_index;
 
 	skb_index = GET_VAL(USERINFO, le64_to_cpu(raw_desc->m0));
 	skb = cp_ring->cp_skb[skb_index];
@@ -160,6 +162,13 @@ static int xgene_enet_tx_completion(struct xgene_enet_desc_ring *cp_ring,
 			       DMA_TO_DEVICE);
 	}
 
+	if (GET_BIT(ET, le64_to_cpu(raw_desc->m3))) {
+		mss_index = GET_VAL(MSS, le64_to_cpu(raw_desc->m3));
+		spin_lock(&pdata->mss_lock);
+		pdata->mss_refcnt[mss_index]--;
+		spin_unlock(&pdata->mss_lock);
+	}
+
 	/* Checking for error */
 	status = GET_VAL(LERR, le64_to_cpu(raw_desc->m0));
 	if (unlikely(status > 2)) {
@@ -178,15 +187,53 @@ static int xgene_enet_tx_completion(struct xgene_enet_desc_ring *cp_ring,
 	return ret;
 }
 
-static u64 xgene_enet_work_msg(struct sk_buff *skb)
+static int xgene_enet_setup_mss(struct net_device *ndev, u32 mss)
+{
+	struct xgene_enet_pdata *pdata = netdev_priv(ndev);
+	bool mss_index_found = false;
+	int mss_index;
+	int i;
+
+	spin_lock(&pdata->mss_lock);
+
+	/* Reuse the slot if MSS matches */
+	for (i = 0; !mss_index_found && i < NUM_MSS_REG; i++) {
+		if (pdata->mss[i] == mss) {
+			pdata->mss_refcnt[i]++;
+			mss_index = i;
+			mss_index_found = true;
+		}
+	}
+
+	/* Overwrite the slot with ref_count = 0 */
+	for (i = 0; !mss_index_found && i < NUM_MSS_REG; i++) {
+		if (!pdata->mss_refcnt[i]) {
+			pdata->mss_refcnt[i]++;
+			pdata->mac_ops->set_mss(pdata, mss, i);
+			pdata->mss[i] = mss;
+			mss_index = i;
+			mss_index_found = true;
+		}
+	}
+
+	spin_unlock(&pdata->mss_lock);
+
+	/* No slots with ref_count = 0 available, return busy */
+	if (!mss_index_found)
+		return -EBUSY;
+
+	return mss_index;
+}
+
+static int xgene_enet_work_msg(struct sk_buff *skb, u64 *hopinfo)
 {
 	struct net_device *ndev = skb->dev;
 	struct iphdr *iph;
 	u8 l3hlen = 0, l4hlen = 0;
 	u8 ethhdr, proto = 0, csum_enable = 0;
-	u64 hopinfo = 0;
 	u32 hdr_len, mss = 0;
 	u32 i, len, nr_frags;
+	int mss_index;
 
 	ethhdr = xgene_enet_hdr_len(skb->data);
 
@@ -226,7 +273,11 @@ static u64 xgene_enet_work_msg(struct sk_buff *skb)
 			if (!mss || ((skb->len - hdr_len) <= mss))
 				goto out;
 
-			hopinfo |= SET_BIT(ET);
+			mss_index = xgene_enet_setup_mss(ndev, mss);
+			if (unlikely(mss_index < 0))
+				return -EBUSY;
+
+			*hopinfo |= SET_BIT(ET) | SET_VAL(MSS, mss_index);
 		}
 	} else if (iph->protocol == IPPROTO_UDP) {
 		l4hlen = UDP_HDR_SIZE;
@@ -234,15 +285,15 @@ static u64 xgene_enet_work_msg(struct sk_buff *skb)
 	}
 out:
 	l3hlen = ip_hdrlen(skb) >> 2;
-	hopinfo |= SET_VAL(TCPHDR, l4hlen) |
-		  SET_VAL(IPHDR, l3hlen) |
-		  SET_VAL(ETHHDR, ethhdr) |
-		  SET_VAL(EC, csum_enable) |
-		  SET_VAL(IS, proto) |
-		  SET_BIT(IC) |
-		  SET_BIT(TYPE_ETH_WORK_MESSAGE);
-
-	return hopinfo;
+	*hopinfo |= SET_VAL(TCPHDR, l4hlen) |
+		    SET_VAL(IPHDR, l3hlen) |
+		    SET_VAL(ETHHDR, ethhdr) |
+		    SET_VAL(EC, csum_enable) |
+		    SET_VAL(IS, proto) |
+		    SET_BIT(IC) |
+		    SET_BIT(TYPE_ETH_WORK_MESSAGE);
+
+	return 0;
 }
 
 static u16 xgene_enet_encode_len(u16 len)
@@ -282,20 +333,22 @@ static int xgene_enet_setup_tx_desc(struct xgene_enet_desc_ring *tx_ring,
 	dma_addr_t dma_addr, pbuf_addr, *frag_dma_addr;
 	skb_frag_t *frag;
 	u16 tail = tx_ring->tail;
-	u64 hopinfo;
+	u64 hopinfo = 0;
 	u32 len, hw_len;
 	u8 ll = 0, nv = 0, idx = 0;
 	bool split = false;
 	u32 size, offset, ell_bytes = 0;
 	u32 i, fidx, nr_frags, count = 1;
+	int ret;
 
 	raw_desc = &tx_ring->raw_desc[tail];
 	tail = (tail + 1) & (tx_ring->slots - 1);
 	memset(raw_desc, 0, sizeof(struct xgene_enet_raw_desc));
 
-	hopinfo = xgene_enet_work_msg(skb);
-	if (!hopinfo)
-		return -EINVAL;
+	ret = xgene_enet_work_msg(skb, &hopinfo);
+	if (ret)
+		return ret;
+
 	raw_desc->m3 = cpu_to_le64(SET_VAL(HENQNUM, tx_ring->dst_ring_num) |
 				   hopinfo);
 
@@ -435,6 +488,9 @@ static netdev_tx_t xgene_enet_start_xmit(struct sk_buff *skb,
 		return NETDEV_TX_OK;
 
 	count = xgene_enet_setup_tx_desc(tx_ring, skb);
+	if (count == -EBUSY)
+		return NETDEV_TX_BUSY;
+
 	if (count <= 0) {
 		dev_kfree_skb_any(skb);
 		return NETDEV_TX_OK;
@@ -1669,7 +1725,7 @@ static int xgene_enet_probe(struct platform_device *pdev)
 
 	if (pdata->phy_mode == PHY_INTERFACE_MODE_XGMII) {
 		ndev->features |= NETIF_F_TSO;
-		pdata->mss = XGENE_ENET_MSS;
+		spin_lock_init(&pdata->mss_lock);
 	}
 	ndev->hw_features = ndev->features;