[RFC PATCH 1/3] wifi: ath11k: reserve headroom when aligning RX buffers

[Mark Ruvald Pedersen]

RXDMA buffers are allocated with extra space for 128-byte alignment, but
the driver tries to move skb->data with skb_pull(). The skb is empty at
that point, so skb_pull() rejects every positive delta and leaves the
data pointer unchanged.

Use skb_reserve() while the skb is empty. The existing extra allocation
space leaves at least DP_RX_BUFFER_SIZE bytes of DMA tailroom after the
reservation.

Fixes: d5c65159f289 ("ath11k: driver for Qualcomm IEEE 802.11ax devices")
Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.9.0.1-02146-QCAHKSWPL_SILICONZ-1
Signed-off-by: Mark Ruvald Pedersen <wabsie at gmail.com>
---
diff --git a/drivers/net/wireless/ath/ath11k/dp_rx.c b/drivers/net/wireless/ath/ath11k/dp_rx.c
index 33425707c..e4ea0c216 100644
--- a/drivers/net/wireless/ath/ath11k/dp_rx.c
+++ b/drivers/net/wireless/ath/ath11k/dp_rx.c
@@ -378,7 +378,7 @@ int ath11k_dp_rxbufs_replenish(struct ath11k_base *ab, int mac_id,
 
 		if (!IS_ALIGNED((unsigned long)skb->data,
 				DP_RX_BUFFER_ALIGN_SIZE)) {
-			skb_pull(skb,
-				 PTR_ALIGN(skb->data, DP_RX_BUFFER_ALIGN_SIZE) -
-				 skb->data);
+			skb_reserve(skb,
+				    PTR_ALIGN(skb->data, DP_RX_BUFFER_ALIGN_SIZE) -
+				    skb->data);
 		}
@@ -2875,7 +2875,7 @@ static struct sk_buff *ath11k_dp_rx_alloc_mon_status_buf(struct ath11k_base *ab,
 
 	if (!IS_ALIGNED((unsigned long)skb->data,
 			DP_RX_BUFFER_ALIGN_SIZE)) {
-		skb_pull(skb, PTR_ALIGN(skb->data, DP_RX_BUFFER_ALIGN_SIZE) -
+		skb_reserve(skb, PTR_ALIGN(skb->data, DP_RX_BUFFER_ALIGN_SIZE) -
 			 skb->data);
 	}