[PATCH RFC 5/5] net:stmmac: asynchronous tx_clean

[Jimmy Perchet <jimmy.perchet@parrot.com>]

Tx descriptor's cleanup and preparation are serialized, which is not necessary
and decrease performance.
In addition TX descriptor's cleanup is performed on NET_RX softirq, this is
confusing.

This patch unserialize tx descriptor's cleanup and preparation
and defer cleanup in workqueue.

Signed-off-by: Jimmy Perchet <jimmy.perchet@parrot.com>
---
 drivers/net/ethernet/stmicro/stmmac/chain_mode.c  |  6 +--
 drivers/net/ethernet/stmicro/stmmac/stmmac.h      |  6 ++-
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 52 +++++++++++++----------
 3 files changed, 37 insertions(+), 27 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/chain_mode.c b/drivers/net/ethernet/stmicro/stmmac/chain_mode.c
index d6ed0ce..8ab83cb 100644
--- a/drivers/net/ethernet/stmicro/stmmac/chain_mode.c
+++ b/drivers/net/ethernet/stmicro/stmmac/chain_mode.c
@@ -120,7 +120,7 @@ static void stmmac_refill_desc3(void *priv_ptr, struct dma_desc *p)
 		 * to keep explicit chaining in the descriptor.
 		 */
 		p->des3 = (unsigned int)(priv->dma_rx_phy +
-					 (((priv->dirty_rx) + 1) %
+					 ((priv->dirty_rx + 1) %
 					  priv->dma_rx_size) *
 					 sizeof(struct dma_desc));
 }
@@ -135,9 +135,9 @@ static void stmmac_clean_desc3(void *priv_ptr, struct dma_desc *p)
 		 * to keep explicit chaining in the descriptor.
 		 */
 		p->des3 = (unsigned int)(priv->dma_tx_phy +
-					 (((priv->dirty_tx + 1) %
+					 ((atomic_read(&priv->dirty_tx) + 1) %
 					   priv->dma_tx_size) *
-					  sizeof(struct dma_desc)));
+					  sizeof(struct dma_desc));
 }
 
 const struct stmmac_chain_mode_ops chain_mode_ops = {
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
index f16a9bd..d5b8906 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
@@ -38,8 +38,8 @@ struct stmmac_priv {
 	struct dma_extended_desc *dma_etx ____cacheline_aligned_in_smp;
 	struct dma_desc *dma_tx;
 	struct sk_buff **tx_skbuff;
-	unsigned int cur_tx;
-	unsigned int dirty_tx;
+	atomic_t cur_tx;
+	atomic_t dirty_tx;
 	unsigned int dma_tx_size;
 	u32 tx_count_frames;
 	u32 tx_coal_frames;
@@ -106,6 +106,8 @@ struct stmmac_priv {
 	u32 adv_ts;
 	int use_riwt;
 	spinlock_t ptp_lock;
+	struct work_struct txclean_work;
+	struct workqueue_struct *wq;
 };
 
 extern int phyaddr;
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 5873246..de614ad 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -48,6 +48,7 @@
 #include <linux/seq_file.h>
 #endif /* CONFIG_STMMAC_DEBUG_FS */
 #include <linux/net_tstamp.h>
+#include <linux/workqueue.h>
 #include "stmmac_ptp.h"
 #include "stmmac.h"
 
@@ -205,7 +206,8 @@ static void print_pkt(unsigned char *buf, int len)
 
 static inline u32 stmmac_tx_avail(struct stmmac_priv *priv)
 {
-	return priv->dirty_tx + priv->dma_tx_size - priv->cur_tx - 1;
+	return atomic_read(&priv->dirty_tx) + priv->dma_tx_size
+					 - atomic_read(&priv->cur_tx) - 1;
 }
 
 /**
@@ -230,7 +232,7 @@ static inline void stmmac_hw_fix_mac_speed(struct stmmac_priv *priv)
 static void stmmac_enable_eee_mode(struct stmmac_priv *priv)
 {
 	/* Check and enter in LPI mode */
-	if ((priv->dirty_tx == priv->cur_tx) &&
+	if ((atomic_read(&priv->dirty_tx) == atomic_read(&priv->cur_tx)) &&
 	    (priv->tx_path_in_lpi_mode == false))
 		priv->hw->mac->set_eee_mode(priv->ioaddr);
 }
@@ -1118,8 +1120,8 @@ static int init_dma_desc_rings(struct net_device *dev)
 		priv->tx_skbuff[i] = NULL;
 	}
 
-	priv->dirty_tx = 0;
-	priv->cur_tx = 0;
+	atomic_set(&priv->dirty_tx, 0);
+	atomic_set(&priv->cur_tx, 0);
 
 	stmmac_clear_descriptors(priv);
 
@@ -1264,17 +1266,17 @@ static void stmmac_dma_operation_mode(int mtu, struct stmmac_priv *priv)
  * @priv: driver private structure
  * Description: it reclaims resources after transmission completes.
  */
-static void stmmac_tx_clean(struct stmmac_priv *priv)
+static void stmmac_tx_clean(struct work_struct *work)
 {
+	struct stmmac_priv *priv =
+			container_of(work, struct stmmac_priv, txclean_work);
 	unsigned int txsize = priv->dma_tx_size;
 
-	spin_lock(&priv->tx_lock);
-
 	priv->xstats.tx_clean++;
 
-	while (priv->dirty_tx != priv->cur_tx) {
+	while (atomic_read(&priv->dirty_tx) != atomic_read(&priv->cur_tx)) {
 		int last;
-		unsigned int entry = priv->dirty_tx % txsize;
+		unsigned int entry = atomic_read(&priv->dirty_tx) % txsize;
 		struct sk_buff *skb = priv->tx_skbuff[entry];
 		struct dma_desc *p;
 
@@ -1308,7 +1310,8 @@ static void stmmac_tx_clean(struct stmmac_priv *priv)
 		}
 		if (netif_msg_tx_done(priv))
 			pr_debug("%s: curr %d, dirty %d\n", __func__,
-				 priv->cur_tx, priv->dirty_tx);
+				 atomic_read(&priv->cur_tx),
+				 atomic_read(&priv->dirty_tx));
 
 		if (likely(priv->tx_skbuff_dma[entry])) {
 			dma_unmap_single(priv->device,
@@ -1326,7 +1329,8 @@ static void stmmac_tx_clean(struct stmmac_priv *priv)
 
 		priv->hw->desc->release_tx_desc(p, priv->mode);
 
-		priv->dirty_tx++;
+		wmb();
+		atomic_inc(&priv->dirty_tx);
 	}
 	if (unlikely(netif_queue_stopped(priv->dev) &&
 		     stmmac_tx_avail(priv) > STMMAC_TX_THRESH(priv))) {
@@ -1344,7 +1348,6 @@ static void stmmac_tx_clean(struct stmmac_priv *priv)
 		stmmac_enable_eee_mode(priv);
 		mod_timer(&priv->eee_ctrl_timer, STMMAC_LPI_T(eee_timer));
 	}
-	spin_unlock(&priv->tx_lock);
 }
 
 static inline void stmmac_enable_dma_irq(struct stmmac_priv *priv)
@@ -1380,8 +1383,8 @@ static void stmmac_tx_err(struct stmmac_priv *priv)
 			priv->hw->desc->init_tx_desc(&priv->dma_tx[i],
 						     priv->mode,
 						     (i == txsize - 1));
-	priv->dirty_tx = 0;
-	priv->cur_tx = 0;
+	atomic_set(&priv->dirty_tx, 0);
+	atomic_set(&priv->cur_tx, 0);
 	priv->hw->dma->start_tx(priv->ioaddr);
 
 	priv->dev->stats.tx_errors++;
@@ -1401,12 +1404,16 @@ static void stmmac_dma_interrupt(struct stmmac_priv *priv)
 	int status;
 
 	status = priv->hw->dma->dma_interrupt(priv->ioaddr, &priv->xstats);
-	if (likely((status & handle_rx)) || (status & handle_tx)) {
+	if (likely(status & handle_rx)) {
 		if (likely(napi_schedule_prep(&priv->napi))) {
 			stmmac_disable_dma_irq(priv);
 			__napi_schedule(&priv->napi);
 		}
 	}
+	if (likely(status & handle_tx))
+		queue_work(priv->wq, &priv->txclean_work);
+
+
 	if (unlikely(status & tx_hard_error_bump_tc)) {
 		/* Try to bump up the dma threshold on this failure */
 		if (unlikely(tc != SF_DMA_MODE) && (tc <= 256)) {
@@ -1596,8 +1603,7 @@ static int stmmac_init_dma_engine(struct stmmac_priv *priv)
 static void stmmac_tx_timer(unsigned long data)
 {
 	struct stmmac_priv *priv = (struct stmmac_priv *)data;
-
-	stmmac_tx_clean(priv);
+	queue_work(priv->wq, &priv->txclean_work);
 }
 
 /**
@@ -1876,7 +1882,7 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
 	if (priv->tx_path_in_lpi_mode)
 		stmmac_disable_eee_mode(priv);
 
-	first_entry = entry = priv->cur_tx % txsize;
+	first_entry = entry = atomic_read(&priv->cur_tx) % txsize;
 
 	csum_insertion = (skb->ip_summed == CHECKSUM_PARTIAL);
 	/* To program the descriptors according to the size of the frame */
@@ -1944,12 +1950,13 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
 	priv->hw->desc->set_tx_owner(first);
 	wmb();
 
-	priv->cur_tx += nb_desc;
+	atomic_add(nb_desc, &priv->cur_tx);
 
 	if (netif_msg_pktdata(priv)) {
 		pr_debug("%s: curr %d dirty=%d entry=%d, first=%p, nfrags=%d",
-			__func__, (priv->cur_tx % txsize),
-			(priv->dirty_tx % txsize), entry, first, nfrags);
+			__func__, (atomic_read(&priv->cur_tx) % txsize),
+			(atomic_read(&priv->dirty_tx) % txsize), entry,
+			first, nfrags);
 
 		if (priv->extend_desc)
 			stmmac_display_ring((void *)priv->dma_etx, txsize, 1);
@@ -2171,7 +2178,6 @@ static int stmmac_poll(struct napi_struct *napi, int budget)
 	int work_done = 0;
 
 	priv->xstats.napi_poll++;
-	stmmac_tx_clean(priv);
 
 	work_done = stmmac_rx(priv, budget);
 	if (work_done < budget) {
@@ -2747,6 +2753,8 @@ struct stmmac_priv *stmmac_dvr_probe(struct device *device,
 
 	spin_lock_init(&priv->lock);
 	spin_lock_init(&priv->tx_lock);
+	priv->wq = create_singlethread_workqueue("stmmac_wq");
+	INIT_WORK(&priv->txclean_work, stmmac_tx_clean);
 
 	ret = register_netdev(ndev);
 	if (ret) {
-- 
1.8.1.2