On Fri, May 31, 2019 at 11:38:23AM +0200, Lorenzo Bianconi wrote:
> Set usb buffer size taking into account skb_shared_info in order to
> not always copy the first part of received frames if A-MSDU is enabled
> for SG capable devices
>
> Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
> ---
> drivers/net/wireless/mediatek/mt76/mt76.h | 3 +++
> drivers/net/wireless/mediatek/mt76/usb.c | 12 ++++++++----
> 2 files changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/wireless/mediatek/mt76/mt76.h b/drivers/net/wireless/mediatek/mt76/mt76.h
> index 74d4edf941d6..7899e9b88b54 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt76.h
> +++ b/drivers/net/wireless/mediatek/mt76/mt76.h
> @@ -32,6 +32,9 @@
> #define MT_RX_BUF_SIZE 2048
> #define MT_SKB_HEAD_LEN 128
>
> +#define MT_BUF_WITH_OVERHEAD(x) \
> + ((x) + SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
> +
> struct mt76_dev;
> struct mt76_wcid;
>
> diff --git a/drivers/net/wireless/mediatek/mt76/usb.c b/drivers/net/wireless/mediatek/mt76/usb.c
> index 2bfc8214c0d8..5081643ce701 100644
> --- a/drivers/net/wireless/mediatek/mt76/usb.c
> +++ b/drivers/net/wireless/mediatek/mt76/usb.c
> @@ -286,7 +286,7 @@ static int
> mt76u_fill_rx_sg(struct mt76_dev *dev, struct mt76_queue *q, struct urb *urb,
> int nsgs, gfp_t gfp)
> {
> - int i;
> + int i, data_size = SKB_WITH_OVERHEAD(q->buf_size);
>
> for (i = 0; i < nsgs; i++) {
> struct page *page;
> @@ -299,7 +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, q->buf_size, offset);
> + sg_set_page(&urb->sg[i], page, data_size, offset);
> }
>
> if (i < nsgs) {
> @@ -311,7 +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 * q->buf_size,
> + urb->transfer_buffer_length = urb->num_sgs * data_size;
> sg_init_marker(urb->sg, urb->num_sgs);
>
> return i ? : -ENOMEM;
> @@ -611,8 +611,12 @@ static int mt76u_alloc_rx(struct mt76_dev *dev)
> if (!q->entry)
> return -ENOMEM;
>
> - q->buf_size = dev->usb.sg_en ? MT_RX_BUF_SIZE : PAGE_SIZE;
> + if (dev->usb.sg_en)
> + q->buf_size = MT_BUF_WITH_OVERHEAD(MT_RX_BUF_SIZE);
I strongly recommend to not doing this. While this should work
in theory creating buffer with size of 2k + some bytes might
trigger various bugs in dma mapping or other low level code.
And skb_shered_info is needed only in first buffer IIUC.
Also this patch seems to make first patch unnecessary except for
non sg_en case (in which I think rx AMSDU is broken anyway),
so I would prefer just to apply first patch.
Stanislaw
