Hi and sorry for late comment.
On Fri, May 31, 2019 at 11:38:22AM +0200, Lorenzo Bianconi wrote:
> Commit f8f527b16db5 ("mt76: usb: use EP max packet aligned buffer sizes
> for rx") breaks A-MSDU support. When A-MSDU is enable the device can
> receive frames up to q->buf_size but they will be discarded in
> mt76u_process_rx_entry since there is no enough room for
> skb_shared_info. Fix the issue reallocating the skb and copying in the
> linear area the first 128B of the received frames and in the frag_list
> the remaining part.
>
> Fixes: f8f527b16db5 ("mt76: usb: use EP max packet aligned buffer sizes for rx")
> Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
> ---
> drivers/net/wireless/mediatek/mt76/mt76.h | 1 +
> drivers/net/wireless/mediatek/mt76/usb.c | 52 +++++++++++++++++++----
> 2 files changed, 44 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/wireless/mediatek/mt76/mt76.h b/drivers/net/wireless/mediatek/mt76/mt76.h
> index 97a1296562d0..74d4edf941d6 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt76.h
> +++ b/drivers/net/wireless/mediatek/mt76/mt76.h
> @@ -30,6 +30,7 @@
> #define MT_TX_RING_SIZE 256
> #define MT_MCU_RING_SIZE 32
> #define MT_RX_BUF_SIZE 2048
> +#define MT_SKB_HEAD_LEN 128
>
> 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 bbaa1365bbda..2bfc8214c0d8 100644
> --- a/drivers/net/wireless/mediatek/mt76/usb.c
> +++ b/drivers/net/wireless/mediatek/mt76/usb.c
> @@ -429,6 +429,48 @@ static int mt76u_get_rx_entry_len(u8 *data, u32 data_len)
> return dma_len;
> }
>
> +static struct sk_buff *
> +mt76u_build_rx_skb(u8 *data, int len, int buf_size,
> + int *nsgs)
> +{
> + int data_len = min(len, MT_SKB_HEAD_LEN);
> + struct sk_buff *skb;
> +
> + if (SKB_WITH_OVERHEAD(buf_size) >= MT_DMA_HDR_LEN + len) {
> + /* fast path */
> + skb = build_skb(data, buf_size);
> + if (!skb)
> + return NULL;
> +
> + skb_reserve(skb, MT_DMA_HDR_LEN);
> + __skb_put(skb, len);
> +
> + return skb;
> + }
> +
> + /* slow path, not enough space for data and
> + * skb_shared_info
> + */
> + skb = alloc_skb(data_len, GFP_ATOMIC);
> + if (!skb)
> + return NULL;
> +
> + skb_put_data(skb, data + MT_DMA_HDR_LEN, data_len);
mt7601u and iwlmvm just copy hdrlen + 8 and put the rest
of the buffer in fragment, which supose to be more efficient,
see comment in iwl_mvm_pass_packet_to_mac80211().
> + data += (data_len + MT_DMA_HDR_LEN);
> + len -= data_len;
> + if (len > 0) {
> + struct page *page = virt_to_head_page(data);
> + int offset = data - (u8 *)page_address(page);
u8 cast not needed.
> + skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags,
> + page, offset, len, buf_size);
> + } else {
> + *nsgs = 0;
This seems to be not necessary or a bug (use first buffer 2 times).
Stanislaw
