mt76: usb: use EP max packet aligned buffer sizes for rx

If buffer size is not usb_endpoint_maxp (512 or 1024 bytes) multiple,
usb host driver has to use bounce buffer and copy data. For RX we can
avoid that since we alreay allocate q->buf_size (2kB) buffers and
mt76usb hardware will not fill more data as rx packet size is limited
by network protocol. However add error message if this assumption
somehow will be not true.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/usb.c

@@ -286,7 +286,6 @@ static int
 mt76u_fill_rx_sg(struct mt76_dev *dev, struct mt76_queue *q, struct urb *urb,
 		 int nsgs, gfp_t gfp)
 {
-	int sglen = SKB_WITH_OVERHEAD(q->buf_size);
 	int i;
 
 	for (i = 0; i < nsgs; i++) {
@@ -300,7 +299,7 @@ mt76u_fill_rx_sg(struct mt76_dev *dev, struct mt76_queue *q, struct urb *urb,
 
 		page = virt_to_head_page(data);
 		offset = data - page_address(page);
-		sg_set_page(&urb->sg[i], page, sglen, offset);
+		sg_set_page(&urb->sg[i], page, q->buf_size, offset);
 	}
 
 	if (i < nsgs) {
@@ -312,7 +311,7 @@ mt76u_fill_rx_sg(struct mt76_dev *dev, struct mt76_queue *q, struct urb *urb,
 	}
 
 	urb->num_sgs = max_t(int, i, urb->num_sgs);
-	urb->transfer_buffer_length = urb->num_sgs * sglen,
+	urb->transfer_buffer_length = urb->num_sgs * q->buf_size,
 	sg_init_marker(urb->sg, urb->num_sgs);
 
 	return i ? : -ENOMEM;
@@ -326,7 +325,7 @@ mt76u_refill_rx(struct mt76_dev *dev, struct urb *urb, int nsgs, gfp_t gfp)
 	if (dev->usb.sg_en) {
 		return mt76u_fill_rx_sg(dev, q, urb, nsgs, gfp);
 	} else {
-		urb->transfer_buffer_length = SKB_WITH_OVERHEAD(q->buf_size);
+		urb->transfer_buffer_length = q->buf_size;
 		urb->transfer_buffer = page_frag_alloc(&q->rx_page,
 						       q->buf_size, gfp);
 		return urb->transfer_buffer ? 0 : -ENOMEM;
@@ -447,8 +446,10 @@ mt76u_process_rx_entry(struct mt76_dev *dev, struct urb *urb)
 		return 0;
 
 	data_len = min_t(int, len, data_len - MT_DMA_HDR_LEN);
-	if (MT_DMA_HDR_LEN + data_len > SKB_WITH_OVERHEAD(q->buf_size))
+	if (MT_DMA_HDR_LEN + data_len > SKB_WITH_OVERHEAD(q->buf_size)) {
+		dev_err_ratelimited(dev->dev, "rx data too big %d\n", data_len);
 		return 0;
+	}
 
 	skb = build_skb(data, q->buf_size);
 	if (!skb)