[PATCH net-next v2 1/3] net: stmmac: Fix NAPI poll in TX path when in multi-queue

[Jose Abreu]

Commit 8fce33317023 introduced the concept of NAPI per-channel and
independent cleaning of TX path.

This is currently breaking performance in some cases. The scenario
happens when all packets are being received in Queue 0 but the TX is
performed in Queue != 0.

Fix this by using different NAPI instances per each TX and RX queue, as
suggested by Florian.

Changes from v1:
	- Pass entire ring size to TX clean path (Florian)

Signed-off-by: Jose Abreu <joabreu@xxxxxxxxxxxx>
Cc: Florian Fainelli <f.fainelli@xxxxxxxxx>
Cc: Joao Pinto <jpinto@xxxxxxxxxxxx>
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Giuseppe Cavallaro <peppe.cavallaro@xxxxxx>
Cc: Alexandre Torgue <alexandre.torgue@xxxxxx>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac.h      |   5 +-
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 114 ++++++++++++----------
 2 files changed, 66 insertions(+), 53 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
index 63e1064b27a2..e697ecd9b0a6 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
@@ -78,11 +78,10 @@ struct stmmac_rx_queue {
 };
 
 struct stmmac_channel {
-	struct napi_struct napi ____cacheline_aligned_in_smp;
+	struct napi_struct rx_napi ____cacheline_aligned_in_smp;
+	struct napi_struct tx_napi ____cacheline_aligned_in_smp;
 	struct stmmac_priv *priv_data;
 	u32 index;
-	int has_rx;
-	int has_tx;
 };
 
 struct stmmac_tc_entry {
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 685d20472358..c193bb1a3322 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -155,7 +155,10 @@ static void stmmac_disable_all_queues(struct stmmac_priv *priv)
 	for (queue = 0; queue < maxq; queue++) {
 		struct stmmac_channel *ch = &priv->channel[queue];
 
-		napi_disable(&ch->napi);
+		if (queue < rx_queues_cnt)
+			napi_disable(&ch->rx_napi);
+		if (queue < tx_queues_cnt)
+			napi_disable(&ch->tx_napi);
 	}
 }
 
@@ -173,7 +176,10 @@ static void stmmac_enable_all_queues(struct stmmac_priv *priv)
 	for (queue = 0; queue < maxq; queue++) {
 		struct stmmac_channel *ch = &priv->channel[queue];
 
-		napi_enable(&ch->napi);
+		if (queue < rx_queues_cnt)
+			napi_enable(&ch->rx_napi);
+		if (queue < tx_queues_cnt)
+			napi_enable(&ch->tx_napi);
 	}
 }
 
@@ -1939,6 +1945,10 @@ static int stmmac_tx_clean(struct stmmac_priv *priv, int budget, u32 queue)
 		mod_timer(&priv->eee_ctrl_timer, STMMAC_LPI_T(eee_timer));
 	}
 
+	/* We still have pending packets, let's call for a new scheduling */
+	if (tx_q->dirty_tx != tx_q->cur_tx)
+		mod_timer(&tx_q->txtimer, STMMAC_COAL_TIMER(10));
+
 	__netif_tx_unlock_bh(netdev_get_tx_queue(priv->dev, queue));
 
 	return count;
@@ -2029,23 +2039,15 @@ static int stmmac_napi_check(struct stmmac_priv *priv, u32 chan)
 	int status = stmmac_dma_interrupt_status(priv, priv->ioaddr,
 						 &priv->xstats, chan);
 	struct stmmac_channel *ch = &priv->channel[chan];
-	bool needs_work = false;
 
-	if ((status & handle_rx) && ch->has_rx) {
-		needs_work = true;
-	} else {
-		status &= ~handle_rx;
-	}
-
-	if ((status & handle_tx) && ch->has_tx) {
-		needs_work = true;
-	} else {
-		status &= ~handle_tx;
+	if ((status & handle_rx) && (chan < priv->plat->rx_queues_to_use)) {
+		stmmac_disable_dma_irq(priv, priv->ioaddr, chan);
+		napi_schedule_irqoff(&ch->rx_napi);
 	}
 
-	if (needs_work && napi_schedule_prep(&ch->napi)) {
+	if ((status & handle_tx) && (chan < priv->plat->tx_queues_to_use)) {
 		stmmac_disable_dma_irq(priv, priv->ioaddr, chan);
-		__napi_schedule(&ch->napi);
+		napi_schedule_irqoff(&ch->tx_napi);
 	}
 
 	return status;
@@ -2241,8 +2243,14 @@ static void stmmac_tx_timer(struct timer_list *t)
 
 	ch = &priv->channel[tx_q->queue_index];
 
-	if (likely(napi_schedule_prep(&ch->napi)))
-		__napi_schedule(&ch->napi);
+	/*
+	 * If NAPI is already running we can miss some events. Let's rearm
+	 * the timer and try again.
+	 */
+	if (likely(napi_schedule_prep(&ch->tx_napi)))
+		__napi_schedule(&ch->tx_napi);
+	else
+		mod_timer(&tx_q->txtimer, STMMAC_COAL_TIMER(10));
 }
 
 /**
@@ -3498,7 +3506,7 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
 			else
 				skb->ip_summed = CHECKSUM_UNNECESSARY;
 
-			napi_gro_receive(&ch->napi, skb);
+			napi_gro_receive(&ch->rx_napi, skb);
 
 			priv->dev->stats.rx_packets++;
 			priv->dev->stats.rx_bytes += frame_len;
@@ -3513,41 +3521,43 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
 	return count;
 }
 
-/**
- *  stmmac_poll - stmmac poll method (NAPI)
- *  @napi : pointer to the napi structure.
- *  @budget : maximum number of packets that the current CPU can receive from
- *	      all interfaces.
- *  Description :
- *  To look at the incoming frames and clear the tx resources.
- */
-static int stmmac_napi_poll(struct napi_struct *napi, int budget)
+static int stmmac_napi_poll_rx(struct napi_struct *napi, int budget)
 {
 	struct stmmac_channel *ch =
-		container_of(napi, struct stmmac_channel, napi);
+		container_of(napi, struct stmmac_channel, rx_napi);
 	struct stmmac_priv *priv = ch->priv_data;
-	int work_done, rx_done = 0, tx_done = 0;
 	u32 chan = ch->index;
+	int work_done;
 
 	priv->xstats.napi_poll++;
 
-	if (ch->has_tx)
-		tx_done = stmmac_tx_clean(priv, budget, chan);
-	if (ch->has_rx)
-		rx_done = stmmac_rx(priv, budget, chan);
+	work_done = stmmac_rx(priv, budget, chan);
+	if (work_done < budget && napi_complete_done(napi, work_done))
+		stmmac_enable_dma_irq(priv, priv->ioaddr, chan);
+	return work_done;
+}
 
-	work_done = max(rx_done, tx_done);
-	work_done = min(work_done, budget);
+static int stmmac_napi_poll_tx(struct napi_struct *napi, int budget)
+{
+	struct stmmac_channel *ch =
+		container_of(napi, struct stmmac_channel, tx_napi);
+	struct stmmac_priv *priv = ch->priv_data;
+	struct stmmac_tx_queue *tx_q;
+	u32 chan = ch->index;
+	int work_done;
+
+	priv->xstats.napi_poll++;
 
-	if (work_done < budget && napi_complete_done(napi, work_done)) {
-		int stat;
+	work_done = stmmac_tx_clean(priv, DMA_TX_SIZE, chan);
+	work_done = min(work_done, budget);
 
+	if (work_done < budget && napi_complete_done(napi, work_done))
 		stmmac_enable_dma_irq(priv, priv->ioaddr, chan);
-		stat = stmmac_dma_interrupt_status(priv, priv->ioaddr,
-						   &priv->xstats, chan);
-		if (stat && napi_reschedule(napi))
-			stmmac_disable_dma_irq(priv, priv->ioaddr, chan);
-	}
+
+	/* Force transmission restart */
+	tx_q = &priv->tx_queue[chan];
+	stmmac_enable_dma_transmission(priv, priv->ioaddr);
+	stmmac_set_tx_tail_ptr(priv, priv->ioaddr, tx_q->tx_tail_addr, chan);
 
 	return work_done;
 }
@@ -4323,13 +4333,14 @@ int stmmac_dvr_probe(struct device *device,
 		ch->priv_data = priv;
 		ch->index = queue;
 
-		if (queue < priv->plat->rx_queues_to_use)
-			ch->has_rx = true;
-		if (queue < priv->plat->tx_queues_to_use)
-			ch->has_tx = true;
-
-		netif_napi_add(ndev, &ch->napi, stmmac_napi_poll,
-			       NAPI_POLL_WEIGHT);
+		if (queue < priv->plat->rx_queues_to_use) {
+			netif_napi_add(ndev, &ch->rx_napi, stmmac_napi_poll_rx,
+				       NAPI_POLL_WEIGHT);
+		}
+		if (queue < priv->plat->tx_queues_to_use) {
+			netif_napi_add(ndev, &ch->tx_napi, stmmac_napi_poll_tx,
+				       NAPI_POLL_WEIGHT);
+		}
 	}
 
 	mutex_init(&priv->lock);
@@ -4385,7 +4396,10 @@ int stmmac_dvr_probe(struct device *device,
 	for (queue = 0; queue < maxq; queue++) {
 		struct stmmac_channel *ch = &priv->channel[queue];
 
-		netif_napi_del(&ch->napi);
+		if (queue < priv->plat->rx_queues_to_use)
+			netif_napi_del(&ch->rx_napi);
+		if (queue < priv->plat->tx_queues_to_use)
+			netif_napi_del(&ch->tx_napi);
 	}
 error_hw_init:
 	destroy_workqueue(priv->wq);
-- 
2.7.4