iwlwifi: use paged Rx

This switches the iwlwifi driver to use paged skb from linear skb for Rx
buffer. So that it relieves some Rx buffer allocation pressure for the
memory subsystem. Currently iwlwifi (4K for 3945) requests 8K bytes for
Rx buffer. Due to the trailing skb_shared_info in the skb->data,
alloc_skb() will do the next order allocation, which is 16K bytes. This
is suboptimal and more likely to fail when the system is under memory
usage pressure. Switching to paged Rx skb lets us allocate the RXB
directly by alloc_pages(), so that only order 1 allocation is required.

It also adjusts the area spin_lock (with IRQ disabled) protected in the
tasklet because tasklet guarentees to run only on one CPU and the new
unprotected code can be preempted by the IRQ handler. This saves us from
spawning another workqueue to make skb_linearize/__pskb_pull_tail happy
(which cannot be called in hard irq context).

Finally, mac80211 doesn't support paged Rx yet. So we linearize the skb
for all the management frames and software decryption or defragmentation
required data frames before handed to mac80211. For all the other frames,
we __pskb_pull_tail 64 bytes in the linear area of the skb for mac80211
to handle them properly.

Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 19 insertions, 23 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl-agn.c b/drivers/net/wireless/iwlwifi/iwl-agn.c
index 0878b34ee586..fc7a51144f0c 100644
--- a/drivers/net/wireless/iwlwifi/iwl-agn.c
+++ b/drivers/net/wireless/iwlwifi/iwl-agn.c
@@ -524,7 +524,7 @@ int iwl_hw_tx_queue_init(struct iwl_priv *priv,
 static void iwl_rx_reply_alive(struct iwl_priv *priv,
 				struct iwl_rx_mem_buffer *rxb)
 {
-	struct iwl_rx_packet *pkt = (struct iwl_rx_packet *)rxb->skb->data;
+	struct iwl_rx_packet *pkt = rxb_addr(rxb);
 	struct iwl_alive_resp *palive;
 	struct delayed_work *pwork;
 
@@ -610,7 +610,7 @@ static void iwl_rx_beacon_notif(struct iwl_priv *priv,
 				struct iwl_rx_mem_buffer *rxb)
 {
 #ifdef CONFIG_IWLWIFI_DEBUG
-	struct iwl_rx_packet *pkt = (struct iwl_rx_packet *)rxb->skb->data;
+	struct iwl_rx_packet *pkt = rxb_addr(rxb);
 	struct iwl4965_beacon_notif *beacon =
 		(struct iwl4965_beacon_notif *)pkt->u.raw;
 	u8 rate = iwl_hw_get_rate(beacon->beacon_notify_hdr.rate_n_flags);
@@ -634,7 +634,7 @@ static void iwl_rx_beacon_notif(struct iwl_priv *priv,
 static void iwl_rx_card_state_notif(struct iwl_priv *priv,
 				    struct iwl_rx_mem_buffer *rxb)
 {
-	struct iwl_rx_packet *pkt = (struct iwl_rx_packet *)rxb->skb->data;
+	struct iwl_rx_packet *pkt = rxb_addr(rxb);
 	u32 flags = le32_to_cpu(pkt->u.card_state_notif.flags);
 	unsigned long status = priv->status;
 
@@ -786,10 +786,10 @@ void iwl_rx_handle(struct iwl_priv *priv)
 
 		rxq->queue[i] = NULL;
 
-		pci_unmap_single(priv->pci_dev, rxb->real_dma_addr,
-				 priv->hw_params.rx_buf_size + 256,
-				 PCI_DMA_FROMDEVICE);
-		pkt = (struct iwl_rx_packet *)rxb->skb->data;
+		pci_unmap_page(priv->pci_dev, rxb->page_dma,
+			       PAGE_SIZE << priv->hw_params.rx_page_order,
+			       PCI_DMA_FROMDEVICE);
+		pkt = rxb_addr(rxb);
 
 		trace_iwlwifi_dev_rx(priv, pkt,
 			le32_to_cpu(pkt->len_n_flags) & FH_RSCSR_FRAME_SIZE_MSK);
@@ -825,10 +825,10 @@ void iwl_rx_handle(struct iwl_priv *priv)
 		}
 
 		if (reclaim) {
-			/* Invoke any callbacks, transfer the skb to caller, and
-			 * fire off the (possibly) blocking iwl_send_cmd()
+			/* Invoke any callbacks, transfer the buffer to caller,
+			 * and fire off the (possibly) blocking iwl_send_cmd()
 			 * as we reclaim the driver command queue */
-			if (rxb && rxb->skb)
+			if (rxb && rxb->page)
 				iwl_tx_cmd_complete(priv, rxb);
 			else
 				IWL_WARN(priv, "Claim null rxb?\n");
@@ -837,10 +837,10 @@ void iwl_rx_handle(struct iwl_priv *priv)
 		/* For now we just don't re-use anything.  We can tweak this
 		 * later to try and re-use notification packets and SKBs that
 		 * fail to Rx correctly */
-		if (rxb->skb != NULL) {
-			priv->alloc_rxb_skb--;
-			dev_kfree_skb_any(rxb->skb);
-			rxb->skb = NULL;
+		if (rxb->page != NULL) {
+			priv->alloc_rxb_page--;
+			__free_pages(rxb->page, priv->hw_params.rx_page_order);
+			rxb->page = NULL;
 		}
 
 		spin_lock_irqsave(&rxq->lock, flags);
@@ -907,6 +907,8 @@ static void iwl_irq_tasklet_legacy(struct iwl_priv *priv)
 	}
 #endif
 
+	spin_unlock_irqrestore(&priv->lock, flags);
+
 	/* Since CSR_INT and CSR_FH_INT_STATUS reads and clears are not
 	 * atomic, make sure that inta covers all the interrupts that
 	 * we've discovered, even if FH interrupt came in just after
@@ -928,8 +930,6 @@ static void iwl_irq_tasklet_legacy(struct iwl_priv *priv)
 
 		handled |= CSR_INT_BIT_HW_ERR;
 
-		spin_unlock_irqrestore(&priv->lock, flags);
-
 		return;
 	}
 
@@ -1056,7 +1056,6 @@ static void iwl_irq_tasklet_legacy(struct iwl_priv *priv)
 			"flags 0x%08lx\n", inta, inta_mask, inta_fh, flags);
 	}
 #endif
-	spin_unlock_irqrestore(&priv->lock, flags);
 }
 
 /* tasklet for iwlagn interrupt */
@@ -1086,6 +1085,9 @@ static void iwl_irq_tasklet(struct iwl_priv *priv)
 				inta, inta_mask);
 	}
 #endif
+
+	spin_unlock_irqrestore(&priv->lock, flags);
+
 	/* saved interrupt in inta variable now we can reset priv->inta */
 	priv->inta = 0;
 
@@ -1101,8 +1103,6 @@ static void iwl_irq_tasklet(struct iwl_priv *priv)
 
 		handled |= CSR_INT_BIT_HW_ERR;
 
-		spin_unlock_irqrestore(&priv->lock, flags);
-
 		return;
 	}
 
@@ -1242,14 +1242,10 @@ static void iwl_irq_tasklet(struct iwl_priv *priv)
 			 inta & ~priv->inta_mask);
 	}
 
-
 	/* Re-enable all interrupts */
 	/* only Re-enable if diabled by irq */
 	if (test_bit(STATUS_INT_ENABLED, &priv->status))
 		iwl_enable_interrupts(priv);
-
-	spin_unlock_irqrestore(&priv->lock, flags);
-
 }