ath10k: use msdu headroom to store txfrag

Instead of allocating sk_buff for a mere 16-byte
tx fragment list buffer use headroom of the
original msdu sk_buff.

This decreases CPU cache pressure and improves
performance.

Measured improvement on AP135 is 560mbps ->
590mbps of UDP TX briding traffic.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

4 files changed, 53 insertions, 53 deletions

diff --git a/drivers/net/wireless/ath/ath10k/core.h b/drivers/net/wireless/ath/ath10k/core.h
index 4563f800a291..292ad4577c98 100644
--- a/drivers/net/wireless/ath/ath10k/core.h
+++ b/drivers/net/wireless/ath/ath10k/core.h
@@ -54,7 +54,9 @@ struct ath10k_skb_cb {
                 u8 vdev_id;
                 u8 tid;
                 bool is_offchan;
-                struct sk_buff *txfrag;
+
+                u8 frag_len;
+                u8 pad_len;
         } __packed htt;
 } __packed;
 
diff --git a/drivers/net/wireless/ath/ath10k/htt_tx.c b/drivers/net/wireless/ath/ath10k/htt_tx.c
index 5e738d80138f..3b93c6a01c6c 100644
--- a/drivers/net/wireless/ath/ath10k/htt_tx.c
+++ b/drivers/net/wireless/ath/ath10k/htt_tx.c
@@ -307,7 +307,8 @@ int ath10k_htt_mgmt_tx(struct ath10k_htt *htt, struct sk_buff *msdu)
         struct device *dev = htt->ar->dev;
         struct sk_buff *txdesc = NULL;
         struct htt_cmd *cmd;
-        u8 vdev_id = ATH10K_SKB_CB(msdu)->htt.vdev_id;
+        struct ath10k_skb_cb *skb_cb = ATH10K_SKB_CB(msdu);
+        u8 vdev_id = skb_cb->htt.vdev_id;
         int len = 0;
         int msdu_id = -1;
         int res;
@@ -350,6 +351,9 @@ int ath10k_htt_mgmt_tx(struct ath10k_htt *htt, struct sk_buff *msdu)
         memcpy(cmd->mgmt_tx.hdr, msdu->data,
                min_t(int, msdu->len, HTT_MGMT_FRM_HDR_DOWNLOAD_LEN));
 
+        skb_cb->htt.frag_len = 0;
+        skb_cb->htt.pad_len = 0;
+
         res = ath10k_htc_send(&htt->ar->htc, htt->eid, txdesc);
         if (res)
                 goto err_unmap_msdu;
@@ -377,13 +381,12 @@ int ath10k_htt_tx(struct ath10k_htt *htt, struct sk_buff *msdu)
         struct htt_cmd *cmd;
         struct htt_data_tx_desc_frag *tx_frags;
         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)msdu->data;
+        struct ath10k_skb_cb *skb_cb = ATH10K_SKB_CB(msdu);
         struct sk_buff *txdesc = NULL;
-        struct sk_buff *txfrag = NULL;
         bool use_frags;
         u8 vdev_id = ATH10K_SKB_CB(msdu)->htt.vdev_id;
         u8 tid;
-        int prefetch_len, desc_len, frag_len;
-        dma_addr_t frags_paddr;
+        int prefetch_len, desc_len;
         int msdu_id = -1;
         int res;
         u8 flags0;
@@ -407,7 +410,6 @@ int ath10k_htt_tx(struct ath10k_htt *htt, struct sk_buff *msdu)
         prefetch_len = roundup(prefetch_len, 4);
 
         desc_len = sizeof(cmd->hdr) + sizeof(cmd->data_tx) + prefetch_len;
-        frag_len = sizeof(*tx_frags) * 2;
 
         txdesc = ath10k_htc_alloc_skb(desc_len);
         if (!txdesc) {
@@ -421,41 +423,44 @@ int ath10k_htt_tx(struct ath10k_htt *htt, struct sk_buff *msdu)
         use_frags = htt->target_version_major < 3 ||
                     !ieee80211_is_mgmt(hdr->frame_control);
 
-        if (use_frags) {
-                txfrag = dev_alloc_skb(frag_len);
-                if (!txfrag) {
-                        res = -ENOMEM;
-                        goto err_free_txdesc;
-                }
-        }
-
         if (!IS_ALIGNED((unsigned long)txdesc->data, 4)) {
                 ath10k_warn("htt alignment check failed. dropping packet.\n");
                 res = -EIO;
-                goto err_free_txfrag;
+                goto err_free_txdesc;
+        }
+
+        if (use_frags) {
+                skb_cb->htt.frag_len = sizeof(*tx_frags) * 2;
+                skb_cb->htt.pad_len = (unsigned long)msdu->data -
+                                      round_down((unsigned long)msdu->data, 4);
+
+                skb_push(msdu, skb_cb->htt.frag_len + skb_cb->htt.pad_len);
+        } else {
+                skb_cb->htt.frag_len = 0;
+                skb_cb->htt.pad_len = 0;
         }
 
         res = ath10k_skb_map(dev, msdu);
         if (res)
-                goto err_free_txfrag;
+                goto err_pull_txfrag;
 
         if (use_frags) {
+                dma_sync_single_for_cpu(dev, skb_cb->paddr, msdu->len,
+                                        DMA_TO_DEVICE);
+
                 /* tx fragment list must be terminated with zero-entry */
-                skb_put(txfrag, frag_len);
-                tx_frags = (struct htt_data_tx_desc_frag *)txfrag->data;
-                tx_frags[0].paddr = __cpu_to_le32(ATH10K_SKB_CB(msdu)->paddr);
-                tx_frags[0].len   = __cpu_to_le32(msdu->len);
+                tx_frags = (struct htt_data_tx_desc_frag *)msdu->data;
+                tx_frags[0].paddr = __cpu_to_le32(skb_cb->paddr +
+                                                  skb_cb->htt.frag_len +
+                                                  skb_cb->htt.pad_len);
+                tx_frags[0].len   = __cpu_to_le32(msdu->len -
+                                                  skb_cb->htt.frag_len -
+                                                  skb_cb->htt.pad_len);
                 tx_frags[1].paddr = __cpu_to_le32(0);
                 tx_frags[1].len   = __cpu_to_le32(0);
 
-                res = ath10k_skb_map(dev, txfrag);
-                if (res)
-                        goto err_unmap_msdu;
-
-                ath10k_dbg(ATH10K_DBG_HTT, "txfrag 0x%llx\n",
-                           (unsigned long long) ATH10K_SKB_CB(txfrag)->paddr);
-                ath10k_dbg_dump(ATH10K_DBG_HTT_DUMP, NULL, "txfrag: ",
-                                txfrag->data, frag_len);
+                dma_sync_single_for_device(dev, skb_cb->paddr, msdu->len,
+                                           DMA_TO_DEVICE);
         }
 
         ath10k_dbg(ATH10K_DBG_HTT, "msdu 0x%llx\n",
@@ -488,35 +493,28 @@ int ath10k_htt_tx(struct ath10k_htt *htt, struct sk_buff *msdu)
         flags1 |= HTT_DATA_TX_DESC_FLAGS1_CKSUM_L3_OFFLOAD;
         flags1 |= HTT_DATA_TX_DESC_FLAGS1_CKSUM_L4_OFFLOAD;
 
-        if (use_frags)
-                frags_paddr = ATH10K_SKB_CB(txfrag)->paddr;
-        else
-                frags_paddr = ATH10K_SKB_CB(msdu)->paddr;
-
         cmd->hdr.msg_type        = HTT_H2T_MSG_TYPE_TX_FRM;
         cmd->data_tx.flags0      = flags0;
         cmd->data_tx.flags1      = __cpu_to_le16(flags1);
-        cmd->data_tx.len         = __cpu_to_le16(msdu->len);
+        cmd->data_tx.len         = __cpu_to_le16(msdu->len -
+                                                 skb_cb->htt.frag_len -
+                                                 skb_cb->htt.pad_len);
         cmd->data_tx.id          = __cpu_to_le16(msdu_id);
-        cmd->data_tx.frags_paddr = __cpu_to_le32(frags_paddr);
+        cmd->data_tx.frags_paddr = __cpu_to_le32(skb_cb->paddr);
         cmd->data_tx.peerid      = __cpu_to_le32(HTT_INVALID_PEERID);
 
-        memcpy(cmd->data_tx.prefetch, msdu->data, prefetch_len);
+        memcpy(cmd->data_tx.prefetch, hdr, prefetch_len);
 
         res = ath10k_htc_send(&htt->ar->htc, htt->eid, txdesc);
         if (res)
-                goto err_restore;
+                goto err_unmap_msdu;
 
         return 0;
 
-err_restore:
-        if (use_frags)
-                ath10k_skb_unmap(dev, txfrag);
 err_unmap_msdu:
         ath10k_skb_unmap(dev, msdu);
-err_free_txfrag:
-        if (use_frags)
-                dev_kfree_skb_any(txfrag);
+err_pull_txfrag:
+        skb_pull(msdu, skb_cb->htt.frag_len + skb_cb->htt.pad_len);
 err_free_txdesc:
         dev_kfree_skb_any(txdesc);
 err_free_msdu_id:
diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
index 9112e6d6f75c..99a9bad3f398 100644
--- a/drivers/net/wireless/ath/ath10k/mac.c
+++ b/drivers/net/wireless/ath/ath10k/mac.c
@@ -3342,6 +3342,10 @@ int ath10k_mac_register(struct ath10k *ar)
                         IEEE80211_HW_WANT_MONITOR_VIF |
                         IEEE80211_HW_AP_LINK_PS;
 
+        /* MSDU can have HTT TX fragment pushed in front. The additional 4
+         * bytes is used for padding/alignment if necessary. */
+        ar->hw->extra_tx_headroom += sizeof(struct htt_data_tx_desc_frag)*2 + 4;
+
         if (ar->ht_cap_info & WMI_HT_CAP_DYNAMIC_SMPS)
                 ar->hw->flags |= IEEE80211_HW_SUPPORTS_DYNAMIC_SMPS;
 
diff --git a/drivers/net/wireless/ath/ath10k/txrx.c b/drivers/net/wireless/ath/ath10k/txrx.c
index 15395afae957..57931d0fae4b 100644
--- a/drivers/net/wireless/ath/ath10k/txrx.c
+++ b/drivers/net/wireless/ath/ath10k/txrx.c
@@ -49,7 +49,8 @@ void ath10k_txrx_tx_unref(struct ath10k_htt *htt,
 {
         struct device *dev = htt->ar->dev;
         struct ieee80211_tx_info *info;
-        struct sk_buff *msdu, *txfrag;
+        struct ath10k_skb_cb *skb_cb;
+        struct sk_buff *msdu;
         int ret;
 
         ath10k_dbg(ATH10K_DBG_HTT, "htt tx completion msdu_id %u discard %d no_ack %d\n",
@@ -62,20 +63,15 @@ void ath10k_txrx_tx_unref(struct ath10k_htt *htt,
         }
 
         msdu = htt->pending_tx[tx_done->msdu_id];
-        txfrag = ATH10K_SKB_CB(msdu)->htt.txfrag;
-
-        if (txfrag) {
-                ret = ath10k_skb_unmap(dev, txfrag);
-                if (ret)
-                        ath10k_warn("txfrag unmap failed (%d)\n", ret);
-
-                dev_kfree_skb_any(txfrag);
-        }
+        skb_cb = ATH10K_SKB_CB(msdu);
 
         ret = ath10k_skb_unmap(dev, msdu);
         if (ret)
                 ath10k_warn("data skb unmap failed (%d)\n", ret);
 
+        if (skb_cb->htt.frag_len)
+                skb_pull(msdu, skb_cb->htt.frag_len + skb_cb->htt.pad_len);
+
         ath10k_report_offchan_tx(htt->ar, msdu);
 
         info = IEEE80211_SKB_CB(msdu);