carl9170: revamp carl9170_tx_prepare

David Miller complained about the driver's excessive use
of variables in __packed structs. While I did not fully
agree with his sole "performance" argument on all accounts.
I do see some room for improvement in hot-paths on
architectures without an efficient access to unaligned
elements.

This first patch (dare I say?) optimizes an important tx
hot-path in the driver: carl9170_tx_prepare.

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --git a/drivers/net/wireless/ath/carl9170/tx.c b/drivers/net/wireless/ath/carl9170/tx.c
index e6be5e6c1723d0274b61169ef61ad5478421331c..b575c865142d64f82f8e072518c0de44e46039cc 100644 (file)
--- a/drivers/net/wireless/ath/carl9170/tx.c
+++ b/drivers/net/wireless/ath/carl9170/tx.c
@@ -760,8 +760,8 @@ static int carl9170_tx_prepare(struct ar9170 *ar, struct sk_buff *skb)
        struct carl9170_tx_info *arinfo;
        unsigned int hw_queue;
        int i;
-       u16 keytype = 0;
-       u16 len, icv = 0;
+       __le16 mac_tmp;
+       u16 len;
        bool ampdu, no_ack;
 
        BUILD_BUG_ON(sizeof(*arinfo) > sizeof(info->rate_driver_data));
@@ -773,6 +773,10 @@ static int carl9170_tx_prepare(struct ar9170 *ar, struct sk_buff *skb)
 
        BUILD_BUG_ON(IEEE80211_TX_MAX_RATES < CARL9170_TX_MAX_RATES);
 
+       BUILD_BUG_ON(AR9170_MAX_VIRTUAL_MAC >
+               ((CARL9170_TX_SUPER_MISC_VIF_ID >>
+                CARL9170_TX_SUPER_MISC_VIF_ID_S) + 1));
+
        hw_queue = ar9170_qmap[carl9170_get_queue(ar, skb)];
 
        hdr = (void *)skb->data;
@@ -793,20 +797,37 @@ static int carl9170_tx_prepare(struct ar9170 *ar, struct sk_buff *skb)
        txc = (void *)skb_push(skb, sizeof(*txc));
        memset(txc, 0, sizeof(*txc));
 
-       ampdu = !!(info->flags & IEEE80211_TX_CTL_AMPDU);
+       SET_VAL(CARL9170_TX_SUPER_MISC_QUEUE, txc->s.misc, hw_queue);
+
+       if (likely(cvif))
+               SET_VAL(CARL9170_TX_SUPER_MISC_VIF_ID, txc->s.misc, cvif->id);
+
+       if (unlikely(info->flags & IEEE80211_TX_CTL_SEND_AFTER_DTIM))
+               txc->s.misc |= CARL9170_TX_SUPER_MISC_CAB;
+
+       if (unlikely(ieee80211_is_probe_resp(hdr->frame_control)))
+               txc->s.misc |= CARL9170_TX_SUPER_MISC_FILL_IN_TSF;
+
+       mac_tmp = cpu_to_le16(AR9170_TX_MAC_HW_DURATION |
+                             AR9170_TX_MAC_BACKOFF);
+       mac_tmp |= cpu_to_le16((hw_queue << AR9170_TX_MAC_QOS_S) &&
+                              AR9170_TX_MAC_QOS);
+
        no_ack = !!(info->flags & IEEE80211_TX_CTL_NO_ACK);
+       if (unlikely(no_ack))
+               mac_tmp |= cpu_to_le16(AR9170_TX_MAC_NO_ACK);
 
        if (info->control.hw_key) {
-               icv = info->control.hw_key->icv_len;
+               len += info->control.hw_key->icv_len;
 
                switch (info->control.hw_key->cipher) {
                case WLAN_CIPHER_SUITE_WEP40:
                case WLAN_CIPHER_SUITE_WEP104:
                case WLAN_CIPHER_SUITE_TKIP:
-                       keytype = AR9170_TX_MAC_ENCR_RC4;
+                       mac_tmp |= cpu_to_le16(AR9170_TX_MAC_ENCR_RC4);
                        break;
                case WLAN_CIPHER_SUITE_CCMP:
-                       keytype = AR9170_TX_MAC_ENCR_AES;
+                       mac_tmp |= cpu_to_le16(AR9170_TX_MAC_ENCR_AES);
                        break;
                default:
                        WARN_ON(1);
@@ -814,48 +835,58 @@ static int carl9170_tx_prepare(struct ar9170 *ar, struct sk_buff *skb)
                }
        }
 
-       BUILD_BUG_ON(AR9170_MAX_VIRTUAL_MAC >
-               ((CARL9170_TX_SUPER_MISC_VIF_ID >>
-                CARL9170_TX_SUPER_MISC_VIF_ID_S) + 1));
-
-       txc->s.len = cpu_to_le16(len + sizeof(*txc));
-       txc->f.length = cpu_to_le16(len + icv + 4);
-       SET_VAL(CARL9170_TX_SUPER_MISC_VIF_ID, txc->s.misc,
-               cvif ? cvif->id : 0);
+       ampdu = !!(info->flags & IEEE80211_TX_CTL_AMPDU);
+       if (ampdu) {
+               unsigned int density, factor;
 
-       txc->f.mac_control = cpu_to_le16(AR9170_TX_MAC_HW_DURATION |
-                                        AR9170_TX_MAC_BACKOFF);
+               if (unlikely(!sta || !cvif))
+                       goto err_out;
 
-       SET_VAL(CARL9170_TX_SUPER_MISC_QUEUE, txc->s.misc, hw_queue);
+               factor = min_t(unsigned int, 1u,
+                        info->control.sta->ht_cap.ampdu_factor);
 
-       txc->f.mac_control |= cpu_to_le16(hw_queue << AR9170_TX_MAC_QOS_S);
-       txc->f.mac_control |= cpu_to_le16(keytype);
-       txc->f.phy_control = cpu_to_le32(0);
+               density = info->control.sta->ht_cap.ampdu_density;
 
-       if (no_ack)
-               txc->f.mac_control |= cpu_to_le16(AR9170_TX_MAC_NO_ACK);
+               if (density) {
+                       /*
+                        * Watch out!
+                        *
+                        * Otus uses slightly different density values than
+                        * those from the 802.11n spec.
+                        */
 
-       if (info->flags & IEEE80211_TX_CTL_SEND_AFTER_DTIM)
-               txc->s.misc |= CARL9170_TX_SUPER_MISC_CAB;
+                       density = max_t(unsigned int, density + 1, 7u);
+               }
 
-       txrate = &info->control.rates[0];
-       if (carl9170_tx_rts_check(ar, txrate, ampdu, no_ack))
-               txc->f.mac_control |= cpu_to_le16(AR9170_TX_MAC_PROT_RTS);
-       else if (carl9170_tx_cts_check(ar, txrate))
-               txc->f.mac_control |= cpu_to_le16(AR9170_TX_MAC_PROT_CTS);
+               SET_VAL(CARL9170_TX_SUPER_AMPDU_DENSITY,
+                       txc->s.ampdu_settings, density);
 
-       SET_VAL(CARL9170_TX_SUPER_RI_TRIES, txc->s.ri[0], txrate->count);
-       txc->f.phy_control |= carl9170_tx_physet(ar, info, txrate);
+               SET_VAL(CARL9170_TX_SUPER_AMPDU_FACTOR,
+                       txc->s.ampdu_settings, factor);
 
-       if (info->flags & IEEE80211_TX_CTL_AMPDU) {
-               for (i = 1; i < CARL9170_TX_MAX_RATES; i++) {
+               for (i = 0; i < CARL9170_TX_MAX_RATES; i++) {
                        txrate = &info->control.rates[i];
-                       if (txrate->idx >= 0)
+                       if (txrate->idx >= 0) {
+                               txc->s.ri[i] =
+                                       CARL9170_TX_SUPER_RI_AMPDU;
+
+                               if (WARN_ON(!(txrate->flags &
+                                             IEEE80211_TX_RC_MCS))) {
+                                       /*
+                                        * Not sure if it's even possible
+                                        * to aggregate non-ht rates with
+                                        * this HW.
+                                        */
+                                       goto err_out;
+                               }
                                continue;
+                       }
 
                        txrate->idx = 0;
                        txrate->count = ar->hw->max_rate_tries;
                }
+
+               mac_tmp |= cpu_to_le16(AR9170_TX_MAC_AGGR);
        }
 
        /*
@@ -878,57 +909,21 @@ static int carl9170_tx_prepare(struct ar9170 *ar, struct sk_buff *skb)
                        txc->s.ri[i] |= (AR9170_TX_MAC_PROT_CTS <<
                                CARL9170_TX_SUPER_RI_ERP_PROT_S);
 
-               /*
-                * unaggregated fallback, in case aggregation
-                * proves to be unsuccessful and unreliable.
-                */
-               if (ampdu && i < 3)
-                       txc->s.ri[i] |= CARL9170_TX_SUPER_RI_AMPDU;
-
                txc->s.rr[i - 1] = carl9170_tx_physet(ar, info, txrate);
        }
 
-       if (ieee80211_is_probe_resp(hdr->frame_control))
-               txc->s.misc |= CARL9170_TX_SUPER_MISC_FILL_IN_TSF;
-
-       if (ampdu) {
-               unsigned int density, factor;
-
-               if (unlikely(!sta || !cvif))
-                       goto err_out;
-
-               density = info->control.sta->ht_cap.ampdu_density;
-               factor = info->control.sta->ht_cap.ampdu_factor;
-
-               if (density) {
-                       /*
-                        * Watch out!
-                        *
-                        * Otus uses slightly different density values than
-                        * those from the 802.11n spec.
-                        */
-
-                       density = max_t(unsigned int, density + 1, 7u);
-               }
-
-               factor = min_t(unsigned int, 1u, factor);
-
-               SET_VAL(CARL9170_TX_SUPER_AMPDU_DENSITY,
-                       txc->s.ampdu_settings, density);
+       txrate = &info->control.rates[0];
+       SET_VAL(CARL9170_TX_SUPER_RI_TRIES, txc->s.ri[0], txrate->count);
 
-               SET_VAL(CARL9170_TX_SUPER_AMPDU_FACTOR,
-                       txc->s.ampdu_settings, factor);
+       if (carl9170_tx_rts_check(ar, txrate, ampdu, no_ack))
+               mac_tmp |= cpu_to_le16(AR9170_TX_MAC_PROT_RTS);
+       else if (carl9170_tx_cts_check(ar, txrate))
+               mac_tmp |= cpu_to_le16(AR9170_TX_MAC_PROT_CTS);
 
-               if (info->control.rates[0].flags & IEEE80211_TX_RC_MCS) {
-                       txc->f.mac_control |= cpu_to_le16(AR9170_TX_MAC_AGGR);
-               } else {
-                       /*
-                        * Not sure if it's even possible to aggregate
-                        * non-ht rates with this HW.
-                        */
-                       WARN_ON_ONCE(1);
-               }
-       }
+       txc->s.len = cpu_to_le16(skb->len);
+       txc->f.length = cpu_to_le16(len + FCS_LEN);
+       txc->f.mac_control = mac_tmp;
+       txc->f.phy_control = carl9170_tx_physet(ar, info, txrate);
 
        arinfo = (void *)info->rate_driver_data;
        arinfo->timeout = jiffies;