wl1271: Allocate TX descriptors more efficiently

On each TX descriptor allocation, a free entry is found by traversing the TX
descriptors array.

Improve this by holding a bitmap of all TX descriptors, and using efficient
bit operations to search for free entries.

Signed-off-by: Ido Yariv <ido@wizery.com>
Reviewed-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>

3 files changed, 24 insertions, 16 deletions

diff --git a/drivers/net/wireless/wl12xx/wl1271.h b/drivers/net/wireless/wl12xx/wl1271.h
index 4a034a3f7148..718e96d97d0b 100644
--- a/drivers/net/wireless/wl12xx/wl1271.h
+++ b/drivers/net/wireless/wl12xx/wl1271.h
@@ -398,6 +398,7 @@ struct wl1271 {
         struct work_struct tx_work;
 
         /* Pending TX frames */
+        unsigned long tx_frames_map[BITS_TO_LONGS(ACX_TX_DESCRIPTORS)];
         struct sk_buff *tx_frames[ACX_TX_DESCRIPTORS];
         int tx_frames_cnt;
 
diff --git a/drivers/net/wireless/wl12xx/wl1271_main.c b/drivers/net/wireless/wl12xx/wl1271_main.c
index 18aff225bf82..0fd472597fa6 100644
--- a/drivers/net/wireless/wl12xx/wl1271_main.c
+++ b/drivers/net/wireless/wl12xx/wl1271_main.c
@@ -2532,6 +2532,7 @@ struct ieee80211_hw *wl1271_alloc_hw(void)
         wl->sg_enabled = true;
         wl->hw_pg_ver = -1;
 
+        memset(wl->tx_frames_map, 0, sizeof(wl->tx_frames_map));
         for (i = 0; i < ACX_TX_DESCRIPTORS; i++)
                 wl->tx_frames[i] = NULL;
 
diff --git a/drivers/net/wireless/wl12xx/wl1271_tx.c b/drivers/net/wireless/wl12xx/wl1271_tx.c
index cf32a77a4ff5..85878e5e7526 100644
--- a/drivers/net/wireless/wl12xx/wl1271_tx.c
+++ b/drivers/net/wireless/wl12xx/wl1271_tx.c
@@ -30,17 +30,26 @@
 #include "wl1271_ps.h"
 #include "wl1271_tx.h"
 
-static int wl1271_tx_id(struct wl1271 *wl, struct sk_buff *skb)
+static int wl1271_alloc_tx_id(struct wl1271 *wl, struct sk_buff *skb)
 {
-        int i;
-        for (i = 0; i < ACX_TX_DESCRIPTORS; i++)
-                if (wl->tx_frames[i] == NULL) {
-                        wl->tx_frames[i] = skb;
-                        wl->tx_frames_cnt++;
-                        return i;
-                }
+        int id;
+
+        id = find_first_zero_bit(wl->tx_frames_map, ACX_TX_DESCRIPTORS);
+        if (id >= ACX_TX_DESCRIPTORS)
+                return -EBUSY;
+
+        __set_bit(id, wl->tx_frames_map);
+        wl->tx_frames[id] = skb;
+        wl->tx_frames_cnt++;
+        return id;
+}
 
-        return -EBUSY;
+static void wl1271_free_tx_id(struct wl1271 *wl, int id)
+{
+        if (__test_and_clear_bit(id, wl->tx_frames_map)) {
+                wl->tx_frames[id] = NULL;
+                wl->tx_frames_cnt--;
+        }
 }
 
 static int wl1271_tx_allocate(struct wl1271 *wl, struct sk_buff *skb, u32 extra,
@@ -55,7 +64,7 @@ static int wl1271_tx_allocate(struct wl1271 *wl, struct sk_buff *skb, u32 extra,
                 return -EAGAIN;
 
         /* allocate free identifier for the packet */
-        id = wl1271_tx_id(wl, skb);
+        id = wl1271_alloc_tx_id(wl, skb);
         if (id < 0)
                 return id;
 
@@ -79,8 +88,7 @@ static int wl1271_tx_allocate(struct wl1271 *wl, struct sk_buff *skb, u32 extra,
                              "tx_allocate: size: %d, blocks: %d, id: %d",
                              total_len, total_blocks, id);
         } else {
-                wl->tx_frames[id] = NULL;
-                wl->tx_frames_cnt--;
+                wl1271_free_tx_id(wl, id);
         }
 
         return ret;
@@ -352,8 +360,7 @@ static void wl1271_tx_complete_packet(struct wl1271 *wl,
 
         /* return the packet to the stack */
         ieee80211_tx_status(wl->hw, skb);
-        wl->tx_frames[result->id] = NULL;
-        wl->tx_frames_cnt--;
+        wl1271_free_tx_id(wl, result->id);
 }
 
 /* Called upon reception of a TX complete interrupt */
@@ -422,11 +429,10 @@ void wl1271_tx_reset(struct wl1271 *wl)
         for (i = 0; i < ACX_TX_DESCRIPTORS; i++)
                 if (wl->tx_frames[i] != NULL) {
                         skb = wl->tx_frames[i];
-                        wl->tx_frames[i] = NULL;
+                        wl1271_free_tx_id(wl, i);
                         wl1271_debug(DEBUG_TX, "freeing skb 0x%p", skb);
                         ieee80211_tx_status(wl->hw, skb);
                 }
-        wl->tx_frames_cnt = 0;
 }
 
 #define WL1271_TX_FLUSH_TIMEOUT 500000