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

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

[Stanislaw Gruszka]

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>
---
 drivers/net/wireless/mediatek/mt76/usb.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/usb.c b/drivers/net/wireless/mediatek/mt76/usb.c
index c299c6591072..025e072cff28 100644
--- a/drivers/net/wireless/mediatek/mt76/usb.c
+++ b/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(dev->dev, "rx data too big %d\n", data_len);
 		return 0;
+	}
 
 	skb = build_skb(data, q->buf_size);
 	if (!skb)
-- 
2.20.1

Re: [PATCH] mt76: usb: use EP max packet aligned buffer sizes for rx

[Felix Fietkau]

On 2019-04-30 09:42, Stanislaw Gruszka wrote:
> 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>
> ---
>  drivers/net/wireless/mediatek/mt76/usb.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/wireless/mediatek/mt76/usb.c b/drivers/net/wireless/mediatek/mt76/usb.c
> index c299c6591072..025e072cff28 100644
> --- a/drivers/net/wireless/mediatek/mt76/usb.c
> +++ b/drivers/net/wireless/mediatek/mt76/usb.c
> @@ -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(dev->dev, "rx data too big %d\n", data_len);
Please use WARN_ON_ONCE here, or at least dev_err_ratelimited if you
think it's necessary to print data_len.

- Felix