p54: implement MRR

This implements multi-rate retry in p54. With lots of help
and testing from Christian and the limiting idea from nbd.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Cc: Christian Lamparter <chunkeey@web.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 108 insertions, 22 deletions

diff --git a/drivers/net/wireless/p54/p54common.c b/drivers/net/wireless/p54/p54common.c
index 65be5eca2340..237090140243 100644
--- a/drivers/net/wireless/p54/p54common.c
+++ b/drivers/net/wireless/p54/p54common.c
@@ -1,9 +1,9 @@
-
 /*
  * Common code for mac80211 Prism54 drivers
  *
  * Copyright (c) 2006, Michael Wu <flamingice@sourmilk.net>
  * Copyright (c) 2007, Christian Lamparter <chunkeey@web.de>
+ * Copyright 2008, Johannes Berg <johannes@sipsolutions.net>
  *
  * Based on the islsm (softmac prism54) driver, which is:
  * Copyright 2004-2006 Jean-Baptiste Note <jbnote@gmail.com>, et al.
@@ -544,6 +544,7 @@ static void p54_rx_frame_sent(struct ieee80211_hw *dev, struct sk_buff *skb)
         u32 freed = 0;
         u32 last_addr = priv->rx_start;
         unsigned long flags;
+        int count, idx;
 
         spin_lock_irqsave(&priv->tx_queue.lock, flags);
         while (entry != (struct sk_buff *)&priv->tx_queue) {
@@ -568,18 +569,39 @@ static void p54_rx_frame_sent(struct ieee80211_hw *dev, struct sk_buff *skb)
                         __skb_unlink(entry, &priv->tx_queue);
                         spin_unlock_irqrestore(&priv->tx_queue.lock, flags);
 
-                        ieee80211_tx_info_clear_status(info);
+                        /*
+                         * Clear manually, ieee80211_tx_info_clear_status would
+                         * clear the counts too and we need them.
+                         */
+                        memset(&info->status.ampdu_ack_len, 0,
+                               sizeof(struct ieee80211_tx_info) -
+                               offsetof(struct ieee80211_tx_info, status.ampdu_ack_len));
+                        BUILD_BUG_ON(offsetof(struct ieee80211_tx_info,
+                                              status.ampdu_ack_len) != 23);
+
                         entry_hdr = (struct p54_control_hdr *) entry->data;
                         entry_data = (struct p54_tx_control_allocdata *) entry_hdr->data;
                         if ((entry_hdr->magic1 & cpu_to_le16(0x4000)) != 0)
                                 pad = entry_data->align[0];
 
-                        priv->tx_stats[entry_data->hw_queue].len--;
-                        if (!(info->flags & IEEE80211_TX_CTL_NO_ACK)) {
-                                if (!(payload->status & 0x01))
-                                        info->flags |= IEEE80211_TX_STAT_ACK;
+                        /* walk through the rates array and adjust the counts */
+                        count = payload->retries;
+                        for (idx = 0; idx < 4; idx++) {
+                                if (count >= info->status.rates[idx].count) {
+                                        count -= info->status.rates[idx].count;
+                                } else if (count > 0) {
+                                        info->status.rates[idx].count = count;
+                                        count = 0;
+                                } else {
+                                        info->status.rates[idx].idx = -1;
+                                        info->status.rates[idx].count = 0;
+                                }
                         }
-                        info->status.rates[0].count = payload->retries;
+
+                        priv->tx_stats[entry_data->hw_queue].len--;
+                        if (!(info->flags & IEEE80211_TX_CTL_NO_ACK) &&
+                            !(payload->status & 0x01))
+                                info->flags |= IEEE80211_TX_STAT_ACK;
                         info->status.ack_signal = p54_rssi_to_dbm(dev,
                                         le16_to_cpu(payload->ack_rssi));
                         skb_pull(entry, sizeof(*hdr) + pad + sizeof(*entry_data));
@@ -802,9 +824,12 @@ static int p54_tx(struct ieee80211_hw *dev, struct sk_buff *skb)
         struct p54_control_hdr *hdr;
         struct p54_tx_control_allocdata *txhdr;
         size_t padding, len;
+        int i, j, ridx;
         u8 rate;
         u8 cts_rate = 0x20;
         u8 rc_flags;
+        u8 calculated_tries[4];
+        u8 nrates = 0, nremaining = 8;
 
         current_queue = &priv->tx_stats[skb_get_queue_mapping(skb) + 4];
         if (unlikely(current_queue->len > current_queue->limit))
@@ -827,23 +852,74 @@ static int p54_tx(struct ieee80211_hw *dev, struct sk_buff *skb)
                 hdr->magic1 = cpu_to_le16(0x0010);
         hdr->len = cpu_to_le16(len);
         hdr->type = (info->flags & IEEE80211_TX_CTL_NO_ACK) ? 0 : cpu_to_le16(1);
-        hdr->retry1 = hdr->retry2 = info->control.rates[0].count;
-
-        /* TODO: add support for alternate retry TX rates */
-        rate = ieee80211_get_tx_rate(dev, info)->hw_value;
-        rc_flags = info->control.rates[0].flags;
-        if (rc_flags & IEEE80211_TX_RC_USE_SHORT_PREAMBLE) {
-                rate |= 0x10;
-                cts_rate |= 0x10;
+        hdr->retry1 = info->control.rates[0].count;
+
+        /*
+         * we register the rates in perfect order, and
+         * RTS/CTS won't happen on 5 GHz
+         */
+        cts_rate = info->control.rts_cts_rate_idx;
+
+        memset(&txhdr->rateset, 0, sizeof(txhdr->rateset));
+
+        /* see how many rates got used */
+        for (i = 0; i < 4; i++) {
+                if (info->control.rates[i].idx < 0)
+                        break;
+                nrates++;
+        }
+
+        /* limit tries to 8/nrates per rate */
+        for (i = 0; i < nrates; i++) {
+                /*
+                 * The magic expression here is equivalent to 8/nrates for
+                 * all values that matter, but avoids division and jumps.
+                 * Note that nrates can only take the values 1 through 4.
+                 */
+                calculated_tries[i] = min_t(int, ((15 >> nrates) | 1) + 1,
+                                                 info->control.rates[i].count);
+                nremaining -= calculated_tries[i];
         }
-        if (rc_flags & IEEE80211_TX_RC_USE_RTS_CTS) {
-                rate |= 0x40;
-                cts_rate |= ieee80211_get_rts_cts_rate(dev, info)->hw_value;
-        } else if (rc_flags & IEEE80211_TX_RC_USE_CTS_PROTECT) {
-                rate |= 0x20;
-                cts_rate |= ieee80211_get_rts_cts_rate(dev, info)->hw_value;
+
+        /* if there are tries left, distribute from back to front */
+        for (i = nrates - 1; nremaining > 0 && i >= 0; i--) {
+                int tmp = info->control.rates[i].count - calculated_tries[i];
+
+                if (tmp <= 0)
+                        continue;
+                /* RC requested more tries at this rate */
+
+                tmp = min_t(int, tmp, nremaining);
+                calculated_tries[i] += tmp;
+                nremaining -= tmp;
         }
-        memset(txhdr->rateset, rate, 8);
+
+        ridx = 0;
+        for (i = 0; i < nrates && ridx < 8; i++) {
+                /* we register the rates in perfect order */
+                rate = info->control.rates[i].idx;
+                if (info->band == IEEE80211_BAND_5GHZ)
+                        rate += 4;
+
+                /* store the count we actually calculated for TX status */
+                info->control.rates[i].count = calculated_tries[i];
+
+                rc_flags = info->control.rates[i].flags;
+                if (rc_flags & IEEE80211_TX_RC_USE_SHORT_PREAMBLE) {
+                        rate |= 0x10;
+                        cts_rate |= 0x10;
+                }
+                if (rc_flags & IEEE80211_TX_RC_USE_RTS_CTS)
+                        rate |= 0x40;
+                else if (rc_flags & IEEE80211_TX_RC_USE_CTS_PROTECT)
+                        rate |= 0x20;
+                for (j = 0; j < calculated_tries[i] && ridx < 8; j++) {
+                        txhdr->rateset[ridx] = rate;
+                        ridx++;
+                }
+        }
+        hdr->retry2 = ridx;
+
         txhdr->key_type = 0;
         txhdr->key_len = 0;
         txhdr->hw_queue = skb_get_queue_mapping(skb) + 4;
@@ -1393,6 +1469,16 @@ struct ieee80211_hw *p54_init_common(size_t priv_data_len)
         priv->tx_stats[4].limit = 5;
         dev->queues = 1;
         priv->noise = -94;
+        /*
+         * We support at most 8 tries no matter which rate they're at,
+         * we cannot support max_rates * max_rate_tries as we set it
+         * here, but setting it correctly to 4/2 or so would limit us
+         * artificially if the RC algorithm wants just two rates, so
+         * let's say 4/7, we'll redistribute it at TX time, see the
+         * comments there.
+         */
+        dev->max_rates = 4;
+        dev->max_rate_tries = 7;
         dev->extra_tx_headroom = sizeof(struct p54_control_hdr) + 4 +
                                  sizeof(struct p54_tx_control_allocdata);