rtlwifi: usb: use usb_alloc_coherent for RX buffers

Use dedicated DMA coherent buffers for RX urbs, to avoid allocation of large
skbuffs in hard-irq context and improve performance.

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 67 insertions, 47 deletions

diff --git a/drivers/net/wireless/rtlwifi/usb.c b/drivers/net/wireless/rtlwifi/usb.c
index b5c80b5d57ef..22f29d75947e 100644
--- a/drivers/net/wireless/rtlwifi/usb.c
+++ b/drivers/net/wireless/rtlwifi/usb.c
@@ -324,6 +324,7 @@ static int _rtl_usb_init_rx(struct ieee80211_hw *hw)
         pr_info("rx_max_size %d, rx_urb_num %d, in_ep %d\n",
                 rtlusb->rx_max_size, rtlusb->rx_urb_num, rtlusb->in_ep);
         init_usb_anchor(&rtlusb->rx_submitted);
+        init_usb_anchor(&rtlusb->rx_cleanup_urbs);
         return 0;
 }
 
@@ -405,40 +406,30 @@ static void rtl_usb_init_sw(struct ieee80211_hw *hw)
         rtlusb->disableHWSM =  true;
 }
 
-#define __RADIO_TAP_SIZE_RSV    32
-
 static void _rtl_rx_completed(struct urb *urb);
 
-static struct sk_buff *_rtl_prep_rx_urb(struct ieee80211_hw *hw,
-                                        struct rtl_usb *rtlusb,
-                                        struct urb *urb,
-                                        gfp_t gfp_mask)
+static int _rtl_prep_rx_urb(struct ieee80211_hw *hw, struct rtl_usb *rtlusb,
+                              struct urb *urb, gfp_t gfp_mask)
 {
-        struct sk_buff *skb;
         struct rtl_priv *rtlpriv = rtl_priv(hw);
+        void *buf;
 
-        skb = __dev_alloc_skb((rtlusb->rx_max_size + __RADIO_TAP_SIZE_RSV),
-                               gfp_mask);
-        if (!skb) {
+        buf = usb_alloc_coherent(rtlusb->udev, rtlusb->rx_max_size, gfp_mask,
+                                 &urb->transfer_dma);
+        if (!buf) {
                 RT_TRACE(rtlpriv, COMP_USB, DBG_EMERG,
-                         "Failed to __dev_alloc_skb!!\n");
-                return ERR_PTR(-ENOMEM);
+                         "Failed to usb_alloc_coherent!!\n");
+                return -ENOMEM;
         }
 
-        /* reserve some space for mac80211's radiotap */
-        skb_reserve(skb, __RADIO_TAP_SIZE_RSV);
         usb_fill_bulk_urb(urb, rtlusb->udev,
                           usb_rcvbulkpipe(rtlusb->udev, rtlusb->in_ep),
-                          skb->data, min(skb_tailroom(skb),
-                          (int)rtlusb->rx_max_size),
-                          _rtl_rx_completed, skb);
+                          buf, rtlusb->rx_max_size, _rtl_rx_completed, rtlusb);
+        urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
 
-        _rtl_install_trx_info(rtlusb, skb, rtlusb->in_ep);
-        return skb;
+        return 0;
 }
 
-#undef __RADIO_TAP_SIZE_RSV
-
 static void _rtl_usb_rx_process_agg(struct ieee80211_hw *hw,
                                     struct sk_buff *skb)
 {
@@ -558,11 +549,11 @@ static void _rtl_rx_pre_process(struct ieee80211_hw *hw, struct sk_buff *skb)
         }
 }
 
+#define __RADIO_TAP_SIZE_RSV    32
+
 static void _rtl_rx_completed(struct urb *_urb)
 {
-        struct sk_buff *skb = (struct sk_buff *)_urb->context;
-        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
-        struct rtl_usb *rtlusb = (struct rtl_usb *)info->rate_driver_data[0];
+        struct rtl_usb *rtlusb = (struct rtl_usb *)_urb->context;
         struct ieee80211_hw *hw = usb_get_intfdata(rtlusb->intf);
         struct rtl_priv *rtlpriv = rtl_priv(hw);
         int err = 0;
@@ -571,28 +562,42 @@ static void _rtl_rx_completed(struct urb *_urb)
                 goto free;
 
         if (likely(0 == _urb->status)) {
-                /* If this code were moved to work queue, would CPU
-                 * utilization be improved?  NOTE: We shall allocate another skb
-                 * and reuse the original one.
+                struct sk_buff *skb;
+                unsigned int size = _urb->actual_length;
+
+                if (size < RTL_RX_DESC_SIZE + sizeof(struct ieee80211_hdr)) {
+                        RT_TRACE(rtlpriv, COMP_USB, DBG_EMERG,
+                                 "Too short packet from bulk IN! (len: %d)\n",
+                                 size);
+                        goto resubmit;
+                }
+
+                skb = dev_alloc_skb(size + __RADIO_TAP_SIZE_RSV);
+                if (!skb) {
+                        RT_TRACE(rtlpriv, COMP_USB, DBG_EMERG,
+                                 "Can't allocate skb for bulk IN!\n");
+                        goto resubmit;
+                }
+
+                _rtl_install_trx_info(rtlusb, skb, rtlusb->in_ep);
+
+                /* reserve some space for mac80211's radiotap */
+                skb_reserve(skb, __RADIO_TAP_SIZE_RSV);
+
+                memcpy(skb_put(skb, size), _urb->transfer_buffer, size);
+
+                /* TODO: Do further processing in tasklet (queue skbs,
+                 * schedule tasklet)
                  */
-                skb_put(skb, _urb->actual_length);
 
                 if (likely(!rtlusb->usb_rx_segregate_hdl)) {
-                        struct sk_buff *_skb;
                         _rtl_usb_rx_process_noagg(hw, skb);
-                        _skb = _rtl_prep_rx_urb(hw, rtlusb, _urb, GFP_ATOMIC);
-                        if (IS_ERR(_skb)) {
-                                err = PTR_ERR(_skb);
-                                RT_TRACE(rtlpriv, COMP_USB, DBG_EMERG,
-                                         "Can't allocate skb for bulk IN!\n");
-                                return;
-                        }
-                        skb = _skb;
-                } else{
+                } else {
                         /* TO DO */
                         _rtl_rx_pre_process(hw, skb);
                         pr_err("rx agg not supported\n");
                 }
+
                 goto resubmit;
         }
 
@@ -608,9 +613,6 @@ static void _rtl_rx_completed(struct urb *_urb)
         }
 
 resubmit:
-        skb_reset_tail_pointer(skb);
-        skb_trim(skb, 0);
-
         usb_anchor_urb(_urb, &rtlusb->rx_submitted);
         err = usb_submit_urb(_urb, GFP_ATOMIC);
         if (unlikely(err)) {
@@ -620,13 +622,31 @@ resubmit:
         return;
 
 free:
-        dev_kfree_skb_irq(skb);
+        /* On some architectures, usb_free_coherent must not be called from
+         * hardirq context. Queue urb to cleanup list.
+         */
+        usb_anchor_urb(_urb, &rtlusb->rx_cleanup_urbs);
+}
+
+#undef __RADIO_TAP_SIZE_RSV
+
+static void _rtl_usb_cleanup_rx(struct ieee80211_hw *hw)
+{
+        struct rtl_usb *rtlusb = rtl_usbdev(rtl_usbpriv(hw));
+        struct urb *urb;
+
+        usb_kill_anchored_urbs(&rtlusb->rx_submitted);
+
+        while ((urb = usb_get_from_anchor(&rtlusb->rx_cleanup_urbs))) {
+                usb_free_coherent(urb->dev, urb->transfer_buffer_length,
+                                urb->transfer_buffer, urb->transfer_dma);
+                usb_free_urb(urb);
+        }
 }
 
 static int _rtl_usb_receive(struct ieee80211_hw *hw)
 {
         struct urb *urb;
-        struct sk_buff *skb;
         int err;
         int i;
         struct rtl_priv *rtlpriv = rtl_priv(hw);
@@ -645,11 +665,10 @@ static int _rtl_usb_receive(struct ieee80211_hw *hw)
                         goto err_out;
                 }
 
-                skb = _rtl_prep_rx_urb(hw, rtlusb, urb, GFP_KERNEL);
-                if (IS_ERR(skb)) {
+                err = _rtl_prep_rx_urb(hw, rtlusb, urb, GFP_KERNEL);
+                if (err < 0) {
                         RT_TRACE(rtlpriv, COMP_USB, DBG_EMERG,
                                  "Failed to prep_rx_urb!!\n");
-                        err = PTR_ERR(skb);
                         usb_free_urb(urb);
                         goto err_out;
                 }
@@ -664,6 +683,7 @@ static int _rtl_usb_receive(struct ieee80211_hw *hw)
 
 err_out:
         usb_kill_anchored_urbs(&rtlusb->rx_submitted);
+        _rtl_usb_cleanup_rx(hw);
         return err;
 }
 
@@ -705,7 +725,7 @@ static void rtl_usb_cleanup(struct ieee80211_hw *hw)
         SET_USB_STOP(rtlusb);
 
         /* clean up rx stuff. */
-        usb_kill_anchored_urbs(&rtlusb->rx_submitted);
+        _rtl_usb_cleanup_rx(hw);
 
         /* clean up tx stuff */
         for (i = 0; i < RTL_USB_MAX_EP_NUM; i++) {