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Date:   Wed, 7 Apr 2021 12:53:42 +0200
From:   Lorenzo Bianconi <lorenzo@kernel.org>
To:     Felix Fietkau <nbd@nbd.name>
Cc:     linux-wireless@vger.kernel.org
Subject: Re: [PATCH] mt76: fix rx amsdu subframe processing
Message-ID: <YG2PNuope0XR1RPK@lore-desk>
References: <20210406182235.14377-1-nbd@nbd.name>
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> When receiving an A-MSDU containing only a single subframe, status->last_=
amsdu
> is set, but no previous head is present in the rx A-MSDU queue.
> In this case, the A-MSDU subframe will be held until the next one is rece=
ived,
> potentially causing significant extra latency.
> Fix this by releasing the frame instead of creating a new queue head if
> last_amsdu is set.

Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>

>=20
> Fixes: c7fd4a5d3f75 ("mt76: mt7915: enable hw rx-amsdu de-aggregation")
> Signed-off-by: Felix Fietkau <nbd@nbd.name>
> ---
>  drivers/net/wireless/mediatek/mt76/mac80211.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>=20
> diff --git a/drivers/net/wireless/mediatek/mt76/mac80211.c b/drivers/net/=
wireless/mediatek/mt76/mac80211.c
> index 7684a8cf00fb..0d92b658b6a6 100644
> --- a/drivers/net/wireless/mediatek/mt76/mac80211.c
> +++ b/drivers/net/wireless/mediatek/mt76/mac80211.c
> @@ -517,10 +517,14 @@ static void mt76_rx_release_burst(struct mt76_phy *=
phy, enum mt76_rxq_id q,
> =20
>  	/* first amsdu subframe */
>  	if (status->amsdu && !phy->rx_amsdu[q].head) {
> +		if (status->last_amsdu) {
> +			nskb =3D skb;
> +			goto reset_burst;
> +		}
>  		phy->rx_amsdu[q].tail =3D &skb_shinfo(skb)->frag_list;
>  		phy->rx_amsdu[q].seqno =3D status->seqno;
>  		phy->rx_amsdu[q].head =3D skb;
> -		goto enqueue;
> +		return;
>  	}
> =20
>  	/* ampdu or out-of-order amsdu subframes */
> @@ -543,7 +547,6 @@ static void mt76_rx_release_burst(struct mt76_phy *ph=
y, enum mt76_rxq_id q,
>  reset_burst:
>  	phy->rx_amsdu[q].head =3D NULL;
>  	phy->rx_amsdu[q].tail =3D NULL;
> -enqueue:
>  	if (nskb)
>  		__skb_queue_tail(&dev->rx_skb[q], nskb);
>  }
> --=20
> 2.30.1
>=20

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