netdev - [PATCH net-next 1/2] net: airoha: Read completion queue data in airoha_qdma_tx_napi

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Message-Id: <20241029-airoha-en7581-tx-napi-work-v1-1-96ad1686b946@kernel.org>
Date: Tue, 29 Oct 2024 13:17:09 +0100
From: Lorenzo Bianconi <lorenzo@...nel.org>
To: Felix Fietkau <nbd@....name>, Sean Wang <sean.wang@...iatek.com>, 
 Mark Lee <Mark-MC.Lee@...iatek.com>, Andrew Lunn <andrew+netdev@...n.ch>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Matthias Brugger <matthias.bgg@...il.com>, 
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Cc: linux-arm-kernel@...ts.infradead.org, 
 linux-mediatek@...ts.infradead.org, netdev@...r.kernel.org, 
 Lorenzo Bianconi <lorenzo@...nel.org>
Subject: [PATCH net-next 1/2] net: airoha: Read completion queue data in
 airoha_qdma_tx_napi_poll()

In order to avoid any possible race, read completion queue head and
pending entry in airoha_qdma_tx_napi_poll routine instead of doing it in
airoha_irq_handler. Remove unused airoha_tx_irq_queue unused fields.
This is a preliminary patch to add Qdisc offload for airoha_eth driver.

Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
---
 drivers/net/ethernet/mediatek/airoha_eth.c | 31 +++++++++++++-----------------
 1 file changed, 13 insertions(+), 18 deletions(-)

diff --git a/drivers/net/ethernet/mediatek/airoha_eth.c b/drivers/net/ethernet/mediatek/airoha_eth.c
index f463a505f5babed3e8e53bf62c92290fc94b3525..6cd8901ed38f0640a8a8f72174c120668b364045 100644
--- a/drivers/net/ethernet/mediatek/airoha_eth.c
+++ b/drivers/net/ethernet/mediatek/airoha_eth.c
@@ -752,11 +752,9 @@ struct airoha_tx_irq_queue {
 	struct airoha_qdma *qdma;

 	struct napi_struct napi;
-	u32 *q;

 	int size;
-	int queued;
-	u16 head;
+	u32 *q;
 };

 struct airoha_hw_stats {
@@ -1656,25 +1654,31 @@ static int airoha_qdma_init_rx(struct airoha_qdma *qdma)
 static int airoha_qdma_tx_napi_poll(struct napi_struct *napi, int budget)
 {
 	struct airoha_tx_irq_queue *irq_q;
+	int id, done = 0, irq_queued;
 	struct airoha_qdma *qdma;
 	struct airoha_eth *eth;
-	int id, done = 0;
+	u32 status, head;

 	irq_q = container_of(napi, struct airoha_tx_irq_queue, napi);
 	qdma = irq_q->qdma;
 	id = irq_q - &qdma->q_tx_irq[0];
 	eth = qdma->eth;

-	while (irq_q->queued > 0 && done < budget) {
-		u32 qid, last, val = irq_q->q[irq_q->head];
+	status = airoha_qdma_rr(qdma, REG_IRQ_STATUS(id));
+	head = FIELD_GET(IRQ_HEAD_IDX_MASK, status);
+	head = head % irq_q->size;
+	irq_queued = FIELD_GET(IRQ_ENTRY_LEN_MASK, status);
+
+	while (irq_queued > 0 && done < budget) {
+		u32 qid, last, val = irq_q->q[head];
 		struct airoha_queue *q;

 		if (val == 0xff)
 			break;

-		irq_q->q[irq_q->head] = 0xff; /* mark as done */
-		irq_q->head = (irq_q->head + 1) % irq_q->size;
-		irq_q->queued--;
+		irq_q->q[head] = 0xff; /* mark as done */
+		head = (head + 1) % irq_q->size;
+		irq_queued--;
 		done++;

 		last = FIELD_GET(IRQ_DESC_IDX_MASK, val);
@@ -2026,20 +2030,11 @@ static irqreturn_t airoha_irq_handler(int irq, void *dev_instance)

 	if (intr[0] & INT_TX_MASK) {
 		for (i = 0; i < ARRAY_SIZE(qdma->q_tx_irq); i++) {
-			struct airoha_tx_irq_queue *irq_q = &qdma->q_tx_irq[i];
-			u32 status, head;
-
 			if (!(intr[0] & TX_DONE_INT_MASK(i)))
 				continue;

 			airoha_qdma_irq_disable(qdma, QDMA_INT_REG_IDX0,
 						TX_DONE_INT_MASK(i));
-
-			status = airoha_qdma_rr(qdma, REG_IRQ_STATUS(i));
-			head = FIELD_GET(IRQ_HEAD_IDX_MASK, status);
-			irq_q->head = head % irq_q->size;
-			irq_q->queued = FIELD_GET(IRQ_ENTRY_LEN_MASK, status);
-
 			napi_schedule(&qdma->q_tx_irq[i].napi);
 		}
 	}

-- 
2.47.0