i40e/i40evf: Break up xmit_descriptor_count from maybe_stop_tx

BugLink: http://bugs.launchpad.net/bugs/1547674

In an upcoming patch I would like to have access to the descriptor count
used for the data portion of the frame.  For this reason I am splitting up
the descriptor count function from the function that stops the ring.

Also in order to try and reduce unnecessary duplication of code I am moving
the slow-path portions of the code out of being inline calls so that we can
just jump to them and process them instead of having to build them into
each function that calls them.
Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
(cherry picked from net-next commit 4ec441df)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/net/ethernet/intel/i40e/i40e_fcoe.c

@@ -1359,16 +1359,26 @@ static netdev_tx_t i40e_fcoe_xmit_frame(struct sk_buff *skb,
 	struct i40e_ring *tx_ring = vsi->tx_rings[skb->queue_mapping];
 	struct i40e_tx_buffer *first;
 	u32 tx_flags = 0;
+	int fso, count;
 	u8 hdr_len = 0;
 	u8 sof = 0;
 	u8 eof = 0;
-	int fso;
 
 	if (i40e_fcoe_set_skb_header(skb))
 		goto out_drop;
 
-	if (!i40e_xmit_descriptor_count(skb, tx_ring))
+	count = i40e_xmit_descriptor_count(skb);
+
+	/* need: 1 descriptor per page * PAGE_SIZE/I40E_MAX_DATA_PER_TXD,
+	 *       + 1 desc for skb_head_len/I40E_MAX_DATA_PER_TXD,
+	 *       + 4 desc gap to avoid the cache line where head is,
+	 *       + 1 desc for context descriptor,
+	 * otherwise try next time
+	 */
+	if (i40e_maybe_stop_tx(tx_ring, count + 4 + 1)) {
+		tx_ring->tx_stats.tx_busy++;
 		return NETDEV_TX_BUSY;
+	}
 
 	/* prepare the xmit flags */
 	if (i40e_tx_prepare_vlan_flags(skb, tx_ring, &tx_flags))

drivers/net/ethernet/intel/i40e/i40e_txrx.c

@@ -2577,7 +2577,7 @@ static void i40e_create_tx_ctx(struct i40e_ring *tx_ring,
  *
  * Returns -EBUSY if a stop is needed, else 0
  **/
-static inline int __i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
+int __i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
 {
 	netif_stop_subqueue(tx_ring->netdev, tx_ring->queue_index);
 	/* Memory barrier before checking head and tail */
@@ -2593,24 +2593,6 @@ static inline int __i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
 	return 0;
 }
 
-/**
- * i40e_maybe_stop_tx - 1st level check for tx stop conditions
- * @tx_ring: the ring to be checked
- * @size:    the size buffer we want to assure is available
- *
- * Returns 0 if stop is not needed
- **/
-#ifdef I40E_FCOE
-inline int i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
-#else
-static inline int i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
-#endif
-{
-	if (likely(I40E_DESC_UNUSED(tx_ring) >= size))
-		return 0;
-	return __i40e_maybe_stop_tx(tx_ring, size);
-}
-
 /**
  * i40e_chk_linearize - Check if there are more than 8 fragments per packet
  * @skb:      send buffer
@@ -2870,43 +2852,6 @@ static inline void i40e_tx_map(struct i40e_ring *tx_ring, struct sk_buff *skb,
 	tx_ring->next_to_use = i;
 }
 
-/**
- * i40e_xmit_descriptor_count - calculate number of tx descriptors needed
- * @skb:     send buffer
- * @tx_ring: ring to send buffer on
- *
- * Returns number of data descriptors needed for this skb. Returns 0 to indicate
- * there is not enough descriptors available in this ring since we need at least
- * one descriptor.
- **/
-#ifdef I40E_FCOE
-inline int i40e_xmit_descriptor_count(struct sk_buff *skb,
-				      struct i40e_ring *tx_ring)
-#else
-static inline int i40e_xmit_descriptor_count(struct sk_buff *skb,
-					     struct i40e_ring *tx_ring)
-#endif
-{
-	unsigned int f;
-	int count = 0;
-
-	/* need: 1 descriptor per page * PAGE_SIZE/I40E_MAX_DATA_PER_TXD,
-	 *       + 1 desc for skb_head_len/I40E_MAX_DATA_PER_TXD,
-	 *       + 4 desc gap to avoid the cache line where head is,
-	 *       + 1 desc for context descriptor,
-	 * otherwise try next time
-	 */
-	for (f = 0; f < skb_shinfo(skb)->nr_frags; f++)
-		count += TXD_USE_COUNT(skb_shinfo(skb)->frags[f].size);
-
-	count += TXD_USE_COUNT(skb_headlen(skb));
-	if (i40e_maybe_stop_tx(tx_ring, count + 4 + 1)) {
-		tx_ring->tx_stats.tx_busy++;
-		return 0;
-	}
-	return count;
-}
-
 /**
  * i40e_xmit_frame_ring - Sends buffer on Tx ring
  * @skb:     send buffer
@@ -2925,14 +2870,24 @@ static netdev_tx_t i40e_xmit_frame_ring(struct sk_buff *skb,
 	__be16 protocol;
 	u32 td_cmd = 0;
 	u8 hdr_len = 0;
+	int tso, count;
 	int tsyn;
-	int tso;
 
 	/* prefetch the data, we'll need it later */
 	prefetch(skb->data);
 
-	if (0 == i40e_xmit_descriptor_count(skb, tx_ring))
+	count = i40e_xmit_descriptor_count(skb);
+
+	/* need: 1 descriptor per page * PAGE_SIZE/I40E_MAX_DATA_PER_TXD,
+	 *       + 1 desc for skb_head_len/I40E_MAX_DATA_PER_TXD,
+	 *       + 4 desc gap to avoid the cache line where head is,
+	 *       + 1 desc for context descriptor,
+	 * otherwise try next time
+	 */
+	if (i40e_maybe_stop_tx(tx_ring, count + 4 + 1)) {
+		tx_ring->tx_stats.tx_busy++;
 		return NETDEV_TX_BUSY;
+	}
 
 	/* prepare the xmit flags */
 	if (i40e_tx_prepare_vlan_flags(skb, tx_ring, &tx_flags))

drivers/net/ethernet/intel/i40e/i40e_txrx.h

@@ -331,13 +331,12 @@ int i40e_napi_poll(struct napi_struct *napi, int budget);
 void i40e_tx_map(struct i40e_ring *tx_ring, struct sk_buff *skb,
 		 struct i40e_tx_buffer *first, u32 tx_flags,
 		 const u8 hdr_len, u32 td_cmd, u32 td_offset);
-int i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size);
-int i40e_xmit_descriptor_count(struct sk_buff *skb, struct i40e_ring *tx_ring);
 int i40e_tx_prepare_vlan_flags(struct sk_buff *skb,
 			       struct i40e_ring *tx_ring, u32 *flags);
 #endif
 void i40e_force_wb(struct i40e_vsi *vsi, struct i40e_q_vector *q_vector);
 u32 i40e_get_tx_pending(struct i40e_ring *ring, bool in_sw);
+int __i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size);
 
 /**
  * i40e_get_head - Retrieve head from head writeback
@@ -352,4 +351,45 @@ static inline u32 i40e_get_head(struct i40e_ring *tx_ring)
 
 	return le32_to_cpu(*(volatile __le32 *)head);
 }
+
+/**
+ * i40e_xmit_descriptor_count - calculate number of Tx descriptors needed
+ * @skb:     send buffer
+ * @tx_ring: ring to send buffer on
+ *
+ * Returns number of data descriptors needed for this skb. Returns 0 to indicate
+ * there is not enough descriptors available in this ring since we need at least
+ * one descriptor.
+ **/
+static inline int i40e_xmit_descriptor_count(struct sk_buff *skb)
+{
+	const struct skb_frag_struct *frag = &skb_shinfo(skb)->frags[0];
+	unsigned int nr_frags = skb_shinfo(skb)->nr_frags;
+	int count = 0, size = skb_headlen(skb);
+
+	for (;;) {
+		count += TXD_USE_COUNT(size);
+
+		if (!nr_frags--)
+			break;
+
+		size = skb_frag_size(frag++);
+	}
+
+	return count;
+}
+
+/**
+ * i40e_maybe_stop_tx - 1st level check for Tx stop conditions
+ * @tx_ring: the ring to be checked
+ * @size:    the size buffer we want to assure is available
+ *
+ * Returns 0 if stop is not needed
+ **/
+static inline int i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
+{
+	if (likely(I40E_DESC_UNUSED(tx_ring) >= size))
+		return 0;
+	return __i40e_maybe_stop_tx(tx_ring, size);
+}
 #endif /* _I40E_TXRX_H_ */

drivers/net/ethernet/intel/i40evf/i40e_txrx.c

@@ -1859,7 +1859,7 @@ static bool i40e_chk_linearize(struct sk_buff *skb, u32 tx_flags)
  *
  * Returns -EBUSY if a stop is needed, else 0
  **/
-static inline int __i40evf_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
+int __i40evf_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
 {
 	netif_stop_subqueue(tx_ring->netdev, tx_ring->queue_index);
 	/* Memory barrier before checking head and tail */
@@ -1875,20 +1875,6 @@ static inline int __i40evf_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
 	return 0;
 }
 
-/**
- * i40evf_maybe_stop_tx - 1st level check for tx stop conditions
- * @tx_ring: the ring to be checked
- * @size:    the size buffer we want to assure is available
- *
- * Returns 0 if stop is not needed
- **/
-static inline int i40evf_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
-{
-	if (likely(I40E_DESC_UNUSED(tx_ring) >= size))
-		return 0;
-	return __i40evf_maybe_stop_tx(tx_ring, size);
-}
-
 /**
  * i40evf_tx_map - Build the Tx descriptor
  * @tx_ring:  ring to send buffer on
@@ -2004,7 +1990,7 @@ static inline void i40evf_tx_map(struct i40e_ring *tx_ring, struct sk_buff *skb,
 	netdev_tx_sent_queue(netdev_get_tx_queue(tx_ring->netdev,
 						 tx_ring->queue_index),
 						 first->bytecount);
-	i40evf_maybe_stop_tx(tx_ring, DESC_NEEDED);
+	i40e_maybe_stop_tx(tx_ring, DESC_NEEDED);
 
 	/* Algorithm to optimize tail and RS bit setting:
 	 * if xmit_more is supported
@@ -2086,38 +2072,6 @@ static inline void i40evf_tx_map(struct i40e_ring *tx_ring, struct sk_buff *skb,
 	tx_ring->next_to_use = i;
 }
 
-/**
- * i40evf_xmit_descriptor_count - calculate number of tx descriptors needed
- * @skb:     send buffer
- * @tx_ring: ring to send buffer on
- *
- * Returns number of data descriptors needed for this skb. Returns 0 to indicate
- * there is not enough descriptors available in this ring since we need at least
- * one descriptor.
- **/
-static inline int i40evf_xmit_descriptor_count(struct sk_buff *skb,
-					       struct i40e_ring *tx_ring)
-{
-	unsigned int f;
-	int count = 0;
-
-	/* need: 1 descriptor per page * PAGE_SIZE/I40E_MAX_DATA_PER_TXD,
-	 *       + 1 desc for skb_head_len/I40E_MAX_DATA_PER_TXD,
-	 *       + 4 desc gap to avoid the cache line where head is,
-	 *       + 1 desc for context descriptor,
-	 * otherwise try next time
-	 */
-	for (f = 0; f < skb_shinfo(skb)->nr_frags; f++)
-		count += TXD_USE_COUNT(skb_shinfo(skb)->frags[f].size);
-
-	count += TXD_USE_COUNT(skb_headlen(skb));
-	if (i40evf_maybe_stop_tx(tx_ring, count + 4 + 1)) {
-		tx_ring->tx_stats.tx_busy++;
-		return 0;
-	}
-	return count;
-}
-
 /**
  * i40e_xmit_frame_ring - Sends buffer on Tx ring
  * @skb:     send buffer
@@ -2136,13 +2090,23 @@ static netdev_tx_t i40e_xmit_frame_ring(struct sk_buff *skb,
 	__be16 protocol;
 	u32 td_cmd = 0;
 	u8 hdr_len = 0;
-	int tso;
+	int tso, count;
 
 	/* prefetch the data, we'll need it later */
 	prefetch(skb->data);
 
-	if (0 == i40evf_xmit_descriptor_count(skb, tx_ring))
+	count = i40e_xmit_descriptor_count(skb);
+
+	/* need: 1 descriptor per page * PAGE_SIZE/I40E_MAX_DATA_PER_TXD,
+	 *       + 1 desc for skb_head_len/I40E_MAX_DATA_PER_TXD,
+	 *       + 4 desc gap to avoid the cache line where head is,
+	 *       + 1 desc for context descriptor,
+	 * otherwise try next time
+	 */
+	if (i40e_maybe_stop_tx(tx_ring, count + 4 + 1)) {
+		tx_ring->tx_stats.tx_busy++;
 		return NETDEV_TX_BUSY;
+	}
 
 	/* prepare the xmit flags */
 	if (i40evf_tx_prepare_vlan_flags(skb, tx_ring, &tx_flags))

drivers/net/ethernet/intel/i40evf/i40e_txrx.h

@@ -326,6 +326,7 @@ void i40evf_free_rx_resources(struct i40e_ring *rx_ring);
 int i40evf_napi_poll(struct napi_struct *napi, int budget);
 void i40evf_force_wb(struct i40e_vsi *vsi, struct i40e_q_vector *q_vector);
 u32 i40evf_get_tx_pending(struct i40e_ring *ring, bool in_sw);
+int __i40evf_maybe_stop_tx(struct i40e_ring *tx_ring, int size);
 
 /**
  * i40e_get_head - Retrieve head from head writeback
@@ -340,4 +341,45 @@ static inline u32 i40e_get_head(struct i40e_ring *tx_ring)
 
 	return le32_to_cpu(*(volatile __le32 *)head);
 }
+
+/**
+ * i40e_xmit_descriptor_count - calculate number of Tx descriptors needed
+ * @skb:     send buffer
+ * @tx_ring: ring to send buffer on
+ *
+ * Returns number of data descriptors needed for this skb. Returns 0 to indicate
+ * there is not enough descriptors available in this ring since we need at least
+ * one descriptor.
+ **/
+static inline int i40e_xmit_descriptor_count(struct sk_buff *skb)
+{
+	const struct skb_frag_struct *frag = &skb_shinfo(skb)->frags[0];
+	unsigned int nr_frags = skb_shinfo(skb)->nr_frags;
+	int count = 0, size = skb_headlen(skb);
+
+	for (;;) {
+		count += TXD_USE_COUNT(size);
+
+		if (!nr_frags--)
+			break;
+
+		size = skb_frag_size(frag++);
+	}
+
+	return count;
+}
+
+/**
+ * i40e_maybe_stop_tx - 1st level check for Tx stop conditions
+ * @tx_ring: the ring to be checked
+ * @size:    the size buffer we want to assure is available
+ *
+ * Returns 0 if stop is not needed
+ **/
+static inline int i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
+{
+	if (likely(I40E_DESC_UNUSED(tx_ring) >= size))
+		return 0;
+	return __i40evf_maybe_stop_tx(tx_ring, size);
+}
 #endif /* _I40E_TXRX_H_ */