[PATCH 2/2] mt76: dma: add rx buffer recycle support

[Lorenzo Bianconi]

Add support for recycling rx buffers if they are not forwarded
to network stack instead of reallocate them from scratch

Signed-off-by: Lorenzo Bianconi <lorenzo.bianc...@redhat.com>
---
 drivers/net/wireless/mediatek/mt76/dma.c  | 60 +++++++++++++++++++++--
 drivers/net/wireless/mediatek/mt76/mt76.h |  3 ++
 2 files changed, 60 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/dma.c 
b/drivers/net/wireless/mediatek/mt76/dma.c
index 1db163c40dcf..eceadfa3f980 100644
--- a/drivers/net/wireless/mediatek/mt76/dma.c
+++ b/drivers/net/wireless/mediatek/mt76/dma.c
@@ -39,6 +39,15 @@ mt76_dma_alloc_queue(struct mt76_dev *dev, struct mt76_queue 
*q)
        if (!q->entry)
                return -ENOMEM;
 
+       /* allocate recycle buffer ring */
+       if (q == &dev->q_rx[MT_RXQ_MCU] ||
+           q == &dev->q_rx[MT_RXQ_MAIN]) {
+               size = q->ndesc * sizeof(*q->recycle);
+               q->recycle = devm_kzalloc(dev->dev, size, GFP_KERNEL);
+               if (!q->recycle)
+                       return -ENOMEM;
+       }
+
        /* clear descriptors */
        for (i = 0; i < q->ndesc; i++)
                q->desc[i].ctrl = cpu_to_le32(MT_DMA_CTL_DMA_DONE);
@@ -317,6 +326,49 @@ int mt76_dma_tx_queue_skb(struct mt76_dev *dev, struct 
mt76_queue *q,
 }
 EXPORT_SYMBOL_GPL(mt76_dma_tx_queue_skb);
 
+/* caller must hold mt76_queue spinlock */
+static u8 *mt76_dma_get_free_buf(struct mt76_queue *q, bool flush)
+{
+       if (q->recycle[q->rhead] || flush) {
+               u8 *buff = q->recycle[q->rhead];
+
+               q->recycle[q->rhead] = NULL;
+               q->rhead = (q->rhead + 1) % q->ndesc;
+               return buff;
+       }
+
+       return page_frag_alloc(&q->rx_page, q->buf_size, GFP_ATOMIC);
+}
+
+static void
+mt76_dma_set_recycle_buf(struct mt76_queue *q, u8 *data)
+{
+       spin_lock_bh(&q->lock);
+       if (!q->recycle[q->rtail]) {
+               q->recycle[q->rtail] = data;
+               q->rtail = (q->rtail + 1) % q->ndesc;
+       } else {
+               skb_free_frag(data);
+       }
+       spin_unlock_bh(&q->lock);
+}
+
+static void
+mt76_dma_free_recycle_ring(struct mt76_queue *q)
+{
+       u8 *buf;
+
+       spin_lock_bh(&q->lock);
+       while (true) {
+               buf = mt76_dma_get_free_buf(q, true);
+               if (!buf)
+                       break;
+
+               skb_free_frag(buf);
+       }
+       spin_unlock_bh(&q->lock);
+}
+
 static int
 mt76_dma_rx_fill(struct mt76_dev *dev, struct mt76_queue *q)
 {
@@ -332,7 +384,7 @@ mt76_dma_rx_fill(struct mt76_dev *dev, struct mt76_queue *q)
        while (q->queued < q->ndesc - 1) {
                struct mt76_queue_buf qbuf;
 
-               buf = page_frag_alloc(&q->rx_page, q->buf_size, GFP_ATOMIC);
+               buf = mt76_dma_get_free_buf(q, false);
                if (!buf)
                        break;
 
@@ -373,6 +425,8 @@ mt76_dma_rx_cleanup(struct mt76_dev *dev, struct mt76_queue 
*q)
        } while (1);
        spin_unlock_bh(&q->lock);
 
+       mt76_dma_free_recycle_ring(q);
+
        if (!q->rx_page.va)
                return;
 
@@ -438,7 +492,7 @@ mt76_dma_rx_process(struct mt76_dev *dev, struct mt76_queue 
*q, int budget)
                        dev_kfree_skb(q->rx_head);
                        q->rx_head = NULL;
 
-                       skb_free_frag(data);
+                       mt76_dma_set_recycle_buf(q, data);
                        continue;
                }
 
@@ -449,7 +503,7 @@ mt76_dma_rx_process(struct mt76_dev *dev, struct mt76_queue 
*q, int budget)
 
                skb = build_skb(data, q->buf_size);
                if (!skb) {
-                       skb_free_frag(data);
+                       mt76_dma_set_recycle_buf(q, data);
                        continue;
                }
                skb_reserve(skb, q->buf_offset);
diff --git a/drivers/net/wireless/mediatek/mt76/mt76.h 
b/drivers/net/wireless/mediatek/mt76/mt76.h
index 5cd508a68609..95546c744494 100644
--- a/drivers/net/wireless/mediatek/mt76/mt76.h
+++ b/drivers/net/wireless/mediatek/mt76/mt76.h
@@ -114,6 +114,9 @@ struct mt76_queue {
        spinlock_t lock;
        struct mt76_queue_entry *entry;
        struct mt76_desc *desc;
+       /* recycle ring */
+       u16 rhead, rtail;
+       u8 **recycle;
 
        struct list_head swq;
        int swq_queued;
-- 
2.19.2