netdev - [PATCH v2 net-next] net: ethernet: mtk_wed: get rid of queue lock for tx queue

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Date:   Thu, 12 Jan 2023 10:21:29 +0100
From:   Lorenzo Bianconi <lorenzo@...nel.org>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, lorenzo.bianconi@...hat.com, nbd@....name,
        john@...ozen.org, sean.wang@...iatek.com, Mark-MC.Lee@...iatek.com,
        sujuan.chen@...iatek.com
Subject: [PATCH v2 net-next] net: ethernet: mtk_wed: get rid of queue lock for tx queue

Similar to MTK Wireless Ethernet Dispatcher (WED) MCU rx queue,
we do not need to protect WED MCU tx queue with a spin lock since
the tx queue is accessed in the two following routines:
- mtk_wed_wo_queue_tx_skb():
  it is run at initialization and during mt7915 normal operation.
  Moreover MCU messages are serialized through MCU mutex.
- mtk_wed_wo_queue_tx_clean():
  it runs just at mt7915 driver module unload when no more messages
  are sent to the MCU.

Remove tx queue spinlock.

Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
---
Changes since v1:
- rebase on top of net-next
---
 drivers/net/ethernet/mediatek/mtk_wed_wo.c | 7 -------
 drivers/net/ethernet/mediatek/mtk_wed_wo.h | 1 -
 2 files changed, 8 deletions(-)

diff --git a/drivers/net/ethernet/mediatek/mtk_wed_wo.c b/drivers/net/ethernet/mediatek/mtk_wed_wo.c
index d32b86499896..69fba29055e9 100644
--- a/drivers/net/ethernet/mediatek/mtk_wed_wo.c
+++ b/drivers/net/ethernet/mediatek/mtk_wed_wo.c
@@ -258,7 +258,6 @@ mtk_wed_wo_queue_alloc(struct mtk_wed_wo *wo, struct mtk_wed_wo_queue *q,
 		       int n_desc, int buf_size, int index,
 		       struct mtk_wed_wo_queue_regs *regs)
 {
-	spin_lock_init(&q->lock);
 	q->regs = *regs;
 	q->n_desc = n_desc;
 	q->buf_size = buf_size;
@@ -290,7 +289,6 @@ mtk_wed_wo_queue_tx_clean(struct mtk_wed_wo *wo, struct mtk_wed_wo_queue *q)
 	struct page *page;
 	int i;
 
-	spin_lock_bh(&q->lock);
 	for (i = 0; i < q->n_desc; i++) {
 		struct mtk_wed_wo_queue_entry *entry = &q->entry[i];
 
@@ -299,7 +297,6 @@ mtk_wed_wo_queue_tx_clean(struct mtk_wed_wo *wo, struct mtk_wed_wo_queue *q)
 		skb_free_frag(entry->buf);
 		entry->buf = NULL;
 	}
-	spin_unlock_bh(&q->lock);
 
 	if (!q->cache.va)
 		return;
@@ -347,8 +344,6 @@ int mtk_wed_wo_queue_tx_skb(struct mtk_wed_wo *wo, struct mtk_wed_wo_queue *q,
 	int ret = 0, index;
 	u32 ctrl;
 
-	spin_lock_bh(&q->lock);
-
 	q->tail = mtk_wed_mmio_r32(wo, q->regs.dma_idx);
 	index = (q->head + 1) % q->n_desc;
 	if (q->tail == index) {
@@ -379,8 +374,6 @@ int mtk_wed_wo_queue_tx_skb(struct mtk_wed_wo *wo, struct mtk_wed_wo_queue *q,
 	mtk_wed_wo_queue_kick(wo, q, q->head);
 	mtk_wed_wo_kickout(wo);
 out:
-	spin_unlock_bh(&q->lock);
-
 	dev_kfree_skb(skb);
 
 	return ret;
diff --git a/drivers/net/ethernet/mediatek/mtk_wed_wo.h b/drivers/net/ethernet/mediatek/mtk_wed_wo.h
index c8fb85795864..dbcf42ce9173 100644
--- a/drivers/net/ethernet/mediatek/mtk_wed_wo.h
+++ b/drivers/net/ethernet/mediatek/mtk_wed_wo.h
@@ -211,7 +211,6 @@ struct mtk_wed_wo_queue {
 	struct mtk_wed_wo_queue_regs regs;
 
 	struct page_frag_cache cache;
-	spinlock_t lock;
 
 	struct mtk_wed_wo_queue_desc *desc;
 	dma_addr_t desc_dma;
-- 
2.39.0