cxgb4: improve credits recovery in TC-MQPRIO Tx path

Request credit update for every half credits consumed, including
the current request. Also, avoid re-trying to post packets when there
are no credits left. The credit update reply via interrupt will
eventually restore the credits and will invoke the Tx path again.

Signed-off-by: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/chelsio/cxgb4/sge.c b/drivers/net/ethernet/chelsio/cxgb4/sge.c
index 6516c45..1359158 100644 (file)
--- a/drivers/net/ethernet/chelsio/cxgb4/sge.c
+++ b/drivers/net/ethernet/chelsio/cxgb4/sge.c
@@ -2091,10 +2091,9 @@ static inline u8 ethofld_calc_tx_flits(struct adapter *adap,
        return flits + nsgl;
 }
 
-static inline void *write_eo_wr(struct adapter *adap,
-                               struct sge_eosw_txq *eosw_txq,
-                               struct sk_buff *skb, struct fw_eth_tx_eo_wr *wr,
-                               u32 hdr_len, u32 wrlen)
+static void *write_eo_wr(struct adapter *adap, struct sge_eosw_txq *eosw_txq,
+                        struct sk_buff *skb, struct fw_eth_tx_eo_wr *wr,
+                        u32 hdr_len, u32 wrlen)
 {
        const struct skb_shared_info *ssi = skb_shinfo(skb);
        struct cpl_tx_pkt_core *cpl;
@@ -2113,7 +2112,8 @@ static inline void *write_eo_wr(struct adapter *adap,
        immd_len += hdr_len;
 
        if (!eosw_txq->ncompl ||
-           eosw_txq->last_compl >= adap->params.ofldq_wr_cred / 2) {
+           (eosw_txq->last_compl + wrlen16) >=
+           (adap->params.ofldq_wr_cred / 2)) {
                compl = true;
                eosw_txq->ncompl++;
                eosw_txq->last_compl = 0;
@@ -2153,8 +2153,8 @@ static inline void *write_eo_wr(struct adapter *adap,
        return cpl;
 }
 
-static void ethofld_hard_xmit(struct net_device *dev,
-                             struct sge_eosw_txq *eosw_txq)
+static int ethofld_hard_xmit(struct net_device *dev,
+                            struct sge_eosw_txq *eosw_txq)
 {
        struct port_info *pi = netdev2pinfo(dev);
        struct adapter *adap = netdev2adap(dev);
@@ -2167,8 +2167,8 @@ static void ethofld_hard_xmit(struct net_device *dev,
        bool skip_eotx_wr = false;
        struct tx_sw_desc *d;
        struct sk_buff *skb;
+       int left, ret = 0;
        u8 flits, ndesc;
-       int left;
 
        eohw_txq = &adap->sge.eohw_txq[eosw_txq->hwqid];
        spin_lock(&eohw_txq->lock);
@@ -2198,11 +2198,19 @@ static void ethofld_hard_xmit(struct net_device *dev,
        wrlen = flits * 8;
        wrlen16 = DIV_ROUND_UP(wrlen, 16);
 
-       /* If there are no CPL credits, then wait for credits
-        * to come back and retry again
+       left = txq_avail(&eohw_txq->q) - ndesc;
+
+       /* If there are no descriptors left in hardware queues or no
+        * CPL credits left in software queues, then wait for them
+        * to come back and retry again. Note that we always request
+        * for credits update via interrupt for every half credits
+        * consumed. So, the interrupt will eventually restore the
+        * credits and invoke the Tx path again.
         */
-       if (unlikely(wrlen16 > eosw_txq->cred))
+       if (unlikely(left < 0 || wrlen16 > eosw_txq->cred)) {
+               ret = -ENOMEM;
                goto out_unlock;
+       }
 
        if (unlikely(skip_eotx_wr)) {
                start = (u64 *)wr;
@@ -2231,7 +2239,8 @@ write_wr_headers:
        sgl = (u64 *)inline_tx_skb_header(skb, &eohw_txq->q, (void *)start,
                                          hdr_len);
        if (data_len) {
-               if (unlikely(cxgb4_map_skb(adap->pdev_dev, skb, d->addr))) {
+               ret = cxgb4_map_skb(adap->pdev_dev, skb, d->addr);
+               if (unlikely(ret)) {
                        memset(d->addr, 0, sizeof(d->addr));
                        eohw_txq->mapping_err++;
                        goto out_unlock;
@@ -2277,12 +2286,13 @@ write_wr_headers:
 
 out_unlock:
        spin_unlock(&eohw_txq->lock);
+       return ret;
 }
 
 static void ethofld_xmit(struct net_device *dev, struct sge_eosw_txq *eosw_txq)
 {
        struct sk_buff *skb;
-       int pktcount;
+       int pktcount, ret;
 
        switch (eosw_txq->state) {
        case CXGB4_EO_STATE_ACTIVE:
@@ -2307,7 +2317,9 @@ static void ethofld_xmit(struct net_device *dev, struct sge_eosw_txq *eosw_txq)
                        continue;
                }
 
-               ethofld_hard_xmit(dev, eosw_txq);
+               ret = ethofld_hard_xmit(dev, eosw_txq);
+               if (ret)
+                       break;
        }
 }