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From:   Oleksandr Natalenko <oleksandr@natalenko.name>
To:     Robin Murphy <robin.murphy@arm.com>,
        Christoph Hellwig <hch@lst.de>,
        Maxime Bizon <mbizon@freebox.fr>,
        Toke =?ISO-8859-1?Q?H=F8iland=2DJ=F8rgensen?= <toke@toke.dk>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Halil Pasic <pasic@linux.ibm.com>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Kalle Valo <kvalo@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Olha Cherevyk <olha.cherevyk@gmail.com>,
        iommu <iommu@lists.linux-foundation.org>,
        linux-wireless <linux-wireless@vger.kernel.org>,
        Netdev <netdev@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable <stable@vger.kernel.org>
Subject: Re: [REGRESSION] Recent swiotlb DMA_FROM_DEVICE fixes break ath9k-based AP
Date:   Fri, 25 Mar 2022 08:12:37 +0100
Message-ID: <4699073.GXAFRqVoOG@natalenko.name>
In-Reply-To: <871qyr9t4e.fsf@toke.dk>
References: <1812355.tdWV9SEqCh@natalenko.name> <d8a1cbf4-a521-78ec-1560-28d855e0913e@arm.com> <871qyr9t4e.fsf@toke.dk>
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Hello.

On =C4=8Dtvrtek 24. b=C5=99ezna 2022 18:07:29 CET Toke H=C3=B8iland-J=C3=B8=
rgensen wrote:
> Right, but is that sync_for_device call really needed? AFAICT, that
> ath9k_hw_process_rxdesc_edma() invocation doesn't actually modify any of
> the data when it returns EINPROGRESS, so could we just skip it? Like
> the patch below? Or am I misunderstanding the semantics here?
>=20
> -Toke
>=20
>=20
> diff --git a/drivers/net/wireless/ath/ath9k/recv.c b/drivers/net/wireless=
/ath/ath9k/recv.c
> index 0c0624a3b40d..19244d4c0ada 100644
> --- a/drivers/net/wireless/ath/ath9k/recv.c
> +++ b/drivers/net/wireless/ath/ath9k/recv.c
> @@ -647,12 +647,8 @@ static bool ath_edma_get_buffers(struct ath_softc *s=
c,
>                                 common->rx_bufsize, DMA_FROM_DEVICE);
> =20
>         ret =3D ath9k_hw_process_rxdesc_edma(ah, rs, skb->data);
> -       if (ret =3D=3D -EINPROGRESS) {
> -               /*let device gain the buffer again*/
> -               dma_sync_single_for_device(sc->dev, bf->bf_buf_addr,
> -                               common->rx_bufsize, DMA_FROM_DEVICE);
> +       if (ret =3D=3D -EINPROGRESS)
>                 return false;
> -       }
> =20
>         __skb_unlink(skb, &rx_edma->rx_fifo);
>         if (ret =3D=3D -EINVAL) {

With this patch and both ddbd89deb7d3+aa6f8dcbab47 in place the AP works fo=
r me.

Thanks.

=2D-=20
Oleksandr Natalenko (post-factum)