netdev - [net-next PATCH v4 3/4] net: stmmac: move TX timer arm after DMA enable

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Date: Wed, 18 Oct 2023 14:35:49 +0200
From: Christian Marangi <ansuelsmth@...il.com>
To: Raju Rangoju <rajur@...lsio.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Jose Abreu <joabreu@...opsys.com>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Ping-Ke Shih <pkshih@...ltek.com>,
	Kalle Valo <kvalo@...nel.org>,
	Simon Horman <horms@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Jiri Pirko <jiri@...nulli.us>,
	Hangbin Liu <liuhangbin@...il.com>,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-stm32@...md-mailman.stormreply.com,
	linux-arm-kernel@...ts.infradead.org,
	linux-wireless@...r.kernel.org
Cc: Christian Marangi <ansuelsmth@...il.com>
Subject: [net-next PATCH v4 3/4] net: stmmac: move TX timer arm after DMA enable

Move TX timer arm call after DMA interrupt is enabled again.

The TX timer arm function changed logic and now is skipped if a napi is
already scheduled. By moving the TX timer arm call after DMA is enabled,
we permit to correctly skip if a DMA interrupt has been fired and a napi
has been scheduled again.

Signed-off-by: Christian Marangi <ansuelsmth@...il.com>
---
 .../net/ethernet/stmicro/stmmac/stmmac_main.c | 22 +++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 5124ee87286c..11055e98efcc 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -2543,9 +2543,13 @@ static void stmmac_bump_dma_threshold(struct stmmac_priv *priv, u32 chan)
  * @priv: driver private structure
  * @budget: napi budget limiting this functions packet handling
  * @queue: TX queue index
+ * @pending_packets: signal to arm the TX coal timer
  * Description: it reclaims the transmit resources after transmission completes.
+ * If some packets still needs to be handled, due to TX coalesce, set
+ * pending_packets to true to make NAPI arm the TX coal timer.
  */
-static int stmmac_tx_clean(struct stmmac_priv *priv, int budget, u32 queue)
+static int stmmac_tx_clean(struct stmmac_priv *priv, int budget, u32 queue,
+			   bool *pending_packets)
 {
 	struct stmmac_tx_queue *tx_q = &priv->dma_conf.tx_queue[queue];
 	struct stmmac_txq_stats *txq_stats = &priv->xstats.txq_stats[queue];
@@ -2706,7 +2710,7 @@ static int stmmac_tx_clean(struct stmmac_priv *priv, int budget, u32 queue)
 
 	/* We still have pending packets, let's call for a new scheduling */
 	if (tx_q->dirty_tx != tx_q->cur_tx)
-		stmmac_tx_timer_arm(priv, queue);
+		*pending_packets = true;
 
 	flags = u64_stats_update_begin_irqsave(&txq_stats->syncp);
 	txq_stats->tx_packets += tx_packets;
@@ -5572,6 +5576,7 @@ static int stmmac_napi_poll_tx(struct napi_struct *napi, int budget)
 		container_of(napi, struct stmmac_channel, tx_napi);
 	struct stmmac_priv *priv = ch->priv_data;
 	struct stmmac_txq_stats *txq_stats;
+	bool pending_packets = false;
 	u32 chan = ch->index;
 	unsigned long flags;
 	int work_done;
@@ -5581,7 +5586,7 @@ static int stmmac_napi_poll_tx(struct napi_struct *napi, int budget)
 	txq_stats->napi_poll++;
 	u64_stats_update_end_irqrestore(&txq_stats->syncp, flags);
 
-	work_done = stmmac_tx_clean(priv, budget, chan);
+	work_done = stmmac_tx_clean(priv, budget, chan, &pending_packets);
 	work_done = min(work_done, budget);
 
 	if (work_done < budget && napi_complete_done(napi, work_done)) {
@@ -5592,6 +5597,10 @@ static int stmmac_napi_poll_tx(struct napi_struct *napi, int budget)
 		spin_unlock_irqrestore(&ch->lock, flags);
 	}
 
+	/* TX still have packet to handle, check if we need to arm tx timer */
+	if (pending_packets)
+		stmmac_tx_timer_arm(priv, chan);
+
 	return work_done;
 }
 
@@ -5600,6 +5609,7 @@ static int stmmac_napi_poll_rxtx(struct napi_struct *napi, int budget)
 	struct stmmac_channel *ch =
 		container_of(napi, struct stmmac_channel, rxtx_napi);
 	struct stmmac_priv *priv = ch->priv_data;
+	bool tx_pending_packets = false;
 	int rx_done, tx_done, rxtx_done;
 	struct stmmac_rxq_stats *rxq_stats;
 	struct stmmac_txq_stats *txq_stats;
@@ -5616,7 +5626,7 @@ static int stmmac_napi_poll_rxtx(struct napi_struct *napi, int budget)
 	txq_stats->napi_poll++;
 	u64_stats_update_end_irqrestore(&txq_stats->syncp, flags);
 
-	tx_done = stmmac_tx_clean(priv, budget, chan);
+	tx_done = stmmac_tx_clean(priv, budget, chan, &tx_pending_packets);
 	tx_done = min(tx_done, budget);
 
 	rx_done = stmmac_rx_zc(priv, budget, chan);
@@ -5641,6 +5651,10 @@ static int stmmac_napi_poll_rxtx(struct napi_struct *napi, int budget)
 		spin_unlock_irqrestore(&ch->lock, flags);
 	}
 
+	/* TX still have packet to handle, check if we need to arm tx timer */
+	if (tx_pending_packets)
+		stmmac_tx_timer_arm(priv, chan);
+
 	return min(rxtx_done, budget - 1);
 }
 
-- 
2.40.1