ath9k: use split rx buffers to get rid of order-1 skb allocations

With this change, less CPU time is spent trying to look for consecutive
pages for rx skbs. This also reduces the socket memory required for IP/UDP
reassembly.
Only two buffers per frame are supported. Frames spanning more buffers
will be dropped, but the buffer size is enough to handle the required
AMSDU size.

Signed-off-by: Jouni Malinen <jouni.malinen@atheros.com>
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

3 files changed, 71 insertions, 24 deletions

diff --git a/drivers/net/wireless/ath/ath9k/ath9k.h b/drivers/net/wireless/ath/ath9k/ath9k.h
index dd9a7d740c98..73db9576af57 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -310,6 +310,8 @@ struct ath_rx {
         struct ath_descdma rxdma;
         struct ath_buf *rx_bufptr;
         struct ath_rx_edma rx_edma[ATH9K_RX_QUEUE_MAX];
+
+        struct sk_buff *frag;
 };
 
 int ath_startrecv(struct ath_softc *sc);
diff --git a/drivers/net/wireless/ath/ath9k/main.c b/drivers/net/wireless/ath/ath9k/main.c
index 422be2675a06..23c016a81bcf 100644
--- a/drivers/net/wireless/ath/ath9k/main.c
+++ b/drivers/net/wireless/ath/ath9k/main.c
@@ -1294,6 +1294,11 @@ static void ath9k_stop(struct ieee80211_hw *hw)
         } else
                 sc->rx.rxlink = NULL;
 
+        if (sc->rx.frag) {
+                dev_kfree_skb_any(sc->rx.frag);
+                sc->rx.frag = NULL;
+        }
+
         /* disable HAL and put h/w to sleep */
         ath9k_hw_disable(ah);
         ath9k_hw_configpcipowersave(ah, 1, 1);
diff --git a/drivers/net/wireless/ath/ath9k/recv.c b/drivers/net/wireless/ath/ath9k/recv.c
index b2b12a293c70..daf171d2f610 100644
--- a/drivers/net/wireless/ath/ath9k/recv.c
+++ b/drivers/net/wireless/ath/ath9k/recv.c
@@ -209,11 +209,6 @@ static int ath_rx_edma_init(struct ath_softc *sc, int nbufs)
         int error = 0, i;
         u32 size;
 
-
-        common->rx_bufsize = roundup(IEEE80211_MAX_MPDU_LEN +
-                                     ah->caps.rx_status_len,
-                                     min(common->cachelsz, (u16)64));
-
         ath9k_hw_set_rx_bufsize(ah, common->rx_bufsize -
                                     ah->caps.rx_status_len);
 
@@ -300,12 +295,12 @@ int ath_rx_init(struct ath_softc *sc, int nbufs)
         sc->sc_flags &= ~SC_OP_RXFLUSH;
         spin_lock_init(&sc->rx.rxbuflock);
 
+        common->rx_bufsize = IEEE80211_MAX_MPDU_LEN / 2 +
+                             sc->sc_ah->caps.rx_status_len;
+
         if (sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_EDMA) {
                 return ath_rx_edma_init(sc, nbufs);
         } else {
-                common->rx_bufsize = roundup(IEEE80211_MAX_MPDU_LEN,
-                                min(common->cachelsz, (u16)64));
-
                 ath_dbg(common, ATH_DBG_CONFIG, "cachelsz %u rxbufsize %u\n",
                         common->cachelsz, common->rx_bufsize);
 
@@ -815,15 +810,9 @@ static bool ath9k_rx_accept(struct ath_common *common,
         if (rx_stats->rs_datalen > (common->rx_bufsize - rx_status_len))
                 return false;
 
-        /*
-         * rs_more indicates chained descriptors which can be used
-         * to link buffers together for a sort of scatter-gather
-         * operation.
-         * reject the frame, we don't support scatter-gather yet and
-         * the frame is probably corrupt anyway
-         */
+        /* Only use error bits from the last fragment */
         if (rx_stats->rs_more)
-                return false;
+                return true;
 
         /*
          * The rx_stats->rs_status will not be set until the end of the
@@ -981,6 +970,10 @@ static int ath9k_rx_skb_preprocess(struct ath_common *common,
         if (!ath9k_rx_accept(common, hdr, rx_status, rx_stats, decrypt_error))
                 return -EINVAL;
 
+        /* Only use status info from the last fragment */
+        if (rx_stats->rs_more)
+                return 0;
+
         ath9k_process_rssi(common, hw, hdr, rx_stats);
 
         if (ath9k_process_rate(common, hw, rx_stats, rx_status))
@@ -1582,7 +1575,7 @@ div_comb_done:
 int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp)
 {
         struct ath_buf *bf;
-        struct sk_buff *skb = NULL, *requeue_skb;
+        struct sk_buff *skb = NULL, *requeue_skb, *hdr_skb;
         struct ieee80211_rx_status *rxs;
         struct ath_hw *ah = sc->sc_ah;
         struct ath_common *common = ath9k_hw_common(ah);
@@ -1633,8 +1626,17 @@ int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp)
                 if (!skb)
                         continue;
 
-                hdr = (struct ieee80211_hdr *) (skb->data + rx_status_len);
-                rxs =  IEEE80211_SKB_RXCB(skb);
+                /*
+                 * Take frame header from the first fragment and RX status from
+                 * the last one.
+                 */
+                if (sc->rx.frag)
+                        hdr_skb = sc->rx.frag;
+                else
+                        hdr_skb = skb;
+
+                hdr = (struct ieee80211_hdr *) (hdr_skb->data + rx_status_len);
+                rxs = IEEE80211_SKB_RXCB(hdr_skb);
 
                 ath_debug_stat_rx(sc, &rs);
 
@@ -1643,12 +1645,12 @@ int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp)
                  * chain it back at the queue without processing it.
                  */
                 if (flush)
-                        goto requeue;
+                        goto requeue_drop_frag;
 
                 retval = ath9k_rx_skb_preprocess(common, hw, hdr, &rs,
                                                  rxs, &decrypt_error);
                 if (retval)
-                        goto requeue;
+                        goto requeue_drop_frag;
 
                 rxs->mactime = (tsf & ~0xffffffffULL) | rs.rs_tstamp;
                 if (rs.rs_tstamp > tsf_lower &&
@@ -1668,7 +1670,7 @@ int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp)
                  * skb and put it at the tail of the sc->rx.rxbuf list for
                  * processing. */
                 if (!requeue_skb)
-                        goto requeue;
+                        goto requeue_drop_frag;
 
                 /* Unmap the frame */
                 dma_unmap_single(sc->dev, bf->bf_buf_addr,
@@ -1679,8 +1681,9 @@ int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp)
                 if (ah->caps.rx_status_len)
                         skb_pull(skb, ah->caps.rx_status_len);
 
-                ath9k_rx_skb_postprocess(common, skb, &rs,
-                                         rxs, decrypt_error);
+                if (!rs.rs_more)
+                        ath9k_rx_skb_postprocess(common, hdr_skb, &rs,
+                                                 rxs, decrypt_error);
 
                 /* We will now give hardware our shiny new allocated skb */
                 bf->bf_mpdu = requeue_skb;
@@ -1697,6 +1700,38 @@ int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp)
                         break;
                 }
 
+                if (rs.rs_more) {
+                        /*
+                         * rs_more indicates chained descriptors which can be
+                         * used to link buffers together for a sort of
+                         * scatter-gather operation.
+                         */
+                        if (sc->rx.frag) {
+                                /* too many fragments - cannot handle frame */
+                                dev_kfree_skb_any(sc->rx.frag);
+                                dev_kfree_skb_any(skb);
+                                skb = NULL;
+                        }
+                        sc->rx.frag = skb;
+                        goto requeue;
+                }
+
+                if (sc->rx.frag) {
+                        int space = skb->len - skb_tailroom(hdr_skb);
+
+                        sc->rx.frag = NULL;
+
+                        if (pskb_expand_head(hdr_skb, 0, space, GFP_ATOMIC) < 0) {
+                                dev_kfree_skb(skb);
+                                goto requeue_drop_frag;
+                        }
+
+                        skb_copy_from_linear_data(skb, skb_put(hdr_skb, skb->len),
+                                                  skb->len);
+                        dev_kfree_skb_any(skb);
+                        skb = hdr_skb;
+                }
+
                 /*
                  * change the default rx antenna if rx diversity chooses the
                  * other antenna 3 times in a row.
@@ -1722,6 +1757,11 @@ int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp)
 
                 ieee80211_rx(hw, skb);
 
+requeue_drop_frag:
+                if (sc->rx.frag) {
+                        dev_kfree_skb_any(sc->rx.frag);
+                        sc->rx.frag = NULL;
+                }
 requeue:
                 if (edma) {
                         list_add_tail(&bf->list, &sc->rx.rxbuf);