[PATCH 2/4] wifi: mt76: dma: add support for mapping skb fragments

[Felix Fietkau <nbd@nbd.name>]

Only supported for skbs without frag_list. This is needed to support
scatter/gather for packets on WLAN devices with A-MSDU offload

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 drivers/net/wireless/mediatek/mt76/dma.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/mediatek/mt76/dma.c b/drivers/net/wireless/mediatek/mt76/dma.c
index 4901aa02b4fb..ceb63b3aaced 100644
--- a/drivers/net/wireless/mediatek/mt76/dma.c
+++ b/drivers/net/wireless/mediatek/mt76/dma.c
@@ -359,12 +359,17 @@ mt76_dma_tx_queue_skb(struct mt76_dev *dev, struct mt76_queue *q,
 		.skb = skb,
 	};
 	struct ieee80211_hw *hw;
-	int len, n = 0, ret = -ENOMEM;
+	int len, i, n = 0, ret = -ENOMEM;
 	struct mt76_txwi_cache *t;
 	struct sk_buff *iter;
 	dma_addr_t addr;
 	u8 *txwi;
 
+	if (skb_shinfo(skb)->nr_frags &&
+	    skb_shinfo(skb)->nr_frags + 1 > dev->hw->max_tx_fragments &&
+	    skb_linearize(skb))
+		goto free_skb;
+
 	t = mt76_get_txwi(dev);
 	if (!t)
 		goto free_skb;
@@ -385,6 +390,22 @@ mt76_dma_tx_queue_skb(struct mt76_dev *dev, struct mt76_queue *q,
 	tx_info.buf[n].addr = addr;
 	tx_info.buf[n++].len = len;
 
+	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
+		skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+
+		if (n == ARRAY_SIZE(tx_info.buf))
+			goto unmap;
+
+		len = skb_frag_size(frag);
+		addr = skb_frag_dma_map(dev->dma_dev, frag, 0, len,
+					DMA_TO_DEVICE);
+		if (unlikely(dma_mapping_error(dev->dma_dev, addr)))
+			goto unmap;
+
+		tx_info.buf[n].addr = addr;
+		tx_info.buf[n++].len = len;
+	}
+
 	skb_walk_frags(skb, iter) {
 		if (n == ARRAY_SIZE(tx_info.buf))
 			goto unmap;
-- 
2.36.1