linux-kernel - Re: [PATCH v2 2/7] dmaengine: hisilicon: Fix CQ head update

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Date:   Thu, 21 Jul 2022 18:57:09 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Jie Hai <haijie1@...wei.com>
Cc:     wangzhou1@...ilicon.com, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/7] dmaengine: hisilicon: Fix CQ head update

On 29-06-22, 11:55, Jie Hai wrote:
> After completion of data transfer of one or multiple descriptors,
> the completion status and the current head pointer to submission
> queue are written into the CQ and interrupt can be generated to
> inform the software. In interrupt process CQ is read and cq_head
> is updated.
> 
> hisi_dma_irq updates cq_head only when the completion status is
> success. When an abnormal interrupt reports, cq_head will not update
> which will cause subsequent interrupt processes read the error CQ
> and never report the correct status.
> 
> This patch updates cq_head whenever CQ is accessed.
> 
> Fixes: e9f08b65250d ("dmaengine: hisilicon: Add Kunpeng DMA engine support")
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Jie Hai <haijie1@...wei.com>
> ---
>  drivers/dma/hisi_dma.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/dma/hisi_dma.c b/drivers/dma/hisi_dma.c
> index 98bc488893cc..7609e6e7eb37 100644
> --- a/drivers/dma/hisi_dma.c
> +++ b/drivers/dma/hisi_dma.c
> @@ -436,12 +436,12 @@ static irqreturn_t hisi_dma_irq(int irq, void *data)
>  	desc = chan->desc;
>  	cqe = chan->cq + chan->cq_head;
>  	if (desc) {
> +		chan->cq_head = (chan->cq_head + 1) %
> +				hdma_dev->chan_depth;

This can look better with single line

> +		hisi_dma_chan_write(hdma_dev->base,
> +				    HISI_DMA_CQ_HEAD_PTR, chan->qp_num,
> +				    chan->cq_head);

maybe two lines?

>  		if (FIELD_GET(STATUS_MASK, cqe->w0) == STATUS_SUCC) {
> -			chan->cq_head = (chan->cq_head + 1) %
> -					hdma_dev->chan_depth;
> -			hisi_dma_chan_write(hdma_dev->base,
> -					    HISI_DMA_CQ_HEAD_PTR, chan->qp_num,
> -					    chan->cq_head);
>  			vchan_cookie_complete(&desc->vd);
>  		} else {
>  			dev_err(&hdma_dev->pdev->dev, "task error!\n");
> -- 
> 2.33.0

-- 
~Vinod