Subject: Re: [REGRESSION] Recent swiotlb DMA_FROM_DEVICE fixes break ath9k-based AP

From: Oleksandr Natalenko <[email-masked]>
Date: Fri, 25 Mar 2022 08:12:37 +0100

Hello.

On čtvrtek 24. března 2022 18:07:29 CET Toke Høiland-Jørgensen 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?
> 
> -Toke
> 
> 
> 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 *sc,
>                                 common->rx_bufsize, DMA_FROM_DEVICE);
>  
>         ret = ath9k_hw_process_rxdesc_edma(ah, rs, skb->data);
> -       if (ret == -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 == -EINPROGRESS)
>                 return false;
> -       }
>  
>         __skb_unlink(skb, &rx_edma->rx_fifo);
>         if (ret == -EINVAL) {

With this patch and both ddbd89deb7d3+aa6f8dcbab47 in place the AP works for me.

Thanks.

-- 
Oleksandr Natalenko (post-factum)