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Date:   Thu, 4 Mar 2021 14:38:33 +0100
From:   Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
To:     sean.wang@mediatek.com
Cc:     nbd@nbd.name, linux-wireless@vger.kernel.org,
        linux-mediatek@lists.infradead.org
Subject: Re: [PATCH 2/3] mt76: mt7663s: make all of packets 4-bytes aligned
 in sdio tx aggregation
Message-ID: <YEDi2VvIBEe7DRuY@lore-desk>
References: <801a2aa986f5486a0e789065feef7b77c612ea7b.1614863741.git.objelf@gmail.com>
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> From: Sean Wang <sean.wang@mediatek.com>
>=20
> Each packet should be padded with the additional zero to become 4-bytes
> alignment in sdio tx aggregation.
>=20
> Fixes: 1522ff731f84 ("mt76: mt7663s: introduce sdio tx aggregation")
> Signed-off-by: Sean Wang <sean.wang@mediatek.com>
> ---
>  drivers/net/wireless/mediatek/mt76/mt7615/sdio_txrx.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>=20
> diff --git a/drivers/net/wireless/mediatek/mt76/mt7615/sdio_txrx.c b/driv=
ers/net/wireless/mediatek/mt76/mt7615/sdio_txrx.c
> index 9fb506f2ace6..2d3b7d1e2c92 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt7615/sdio_txrx.c
> +++ b/drivers/net/wireless/mediatek/mt76/mt7615/sdio_txrx.c
> @@ -218,6 +218,7 @@ static int mt7663s_tx_run_queue(struct mt76_dev *dev,=
 struct mt76_queue *q)
>  	int qid, err, nframes =3D 0, len =3D 0, pse_sz =3D 0, ple_sz =3D 0;
>  	bool mcu =3D q =3D=3D dev->q_mcu[MT_MCUQ_WM];
>  	struct mt76_sdio *sdio =3D &dev->sdio;
> +	u8 pad;
> =20
>  	qid =3D mcu ? ARRAY_SIZE(sdio->xmit_buf) - 1 : q->qid;
>  	while (q->first !=3D q->head) {
> @@ -234,7 +235,8 @@ static int mt7663s_tx_run_queue(struct mt76_dev *dev,=
 struct mt76_queue *q)
>  			goto next;
>  		}
> =20
> -		if (len + e->skb->len + 4 > MT76S_XMIT_BUF_SZ)
> +		pad =3D roundup(e->skb->len, 4) - e->skb->len;
> +		if (len + e->skb->len + pad + 4 > MT76S_XMIT_BUF_SZ)
>  			break;
> =20
>  		if (mt7663s_tx_pick_quota(sdio, mcu, e->buf_sz, &pse_sz,
> @@ -252,6 +254,9 @@ static int mt7663s_tx_run_queue(struct mt76_dev *dev,=
 struct mt76_queue *q)
>  			len +=3D iter->len;
>  			nframes++;
>  		}
> +
> +		memset(sdio->xmit_buf[qid] + len, 0, pad);
> +		len +=3D pad;

maybe it is better to do something like:

		if (unlikely(pad)) {
			memset(sdio->xmit_buf[qid] + len, 0, pad);
			len +=3D pad;
		}

Regards,
Lorenzo

>  next:
>  		q->first =3D (q->first + 1) % q->ndesc;
>  		e->done =3D true;
> --=20
> 2.25.1

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