linux-kernel - Re: [PATCH 3/3] dmaengine: ioat: adding missed issue

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Date:   Wed, 22 Apr 2020 07:21:10 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     leonid.ravich@...l.com, dmaengine@...r.kernel.org
Cc:     lravich@...il.com, Dan Williams <dan.j.williams@...el.com>,
        Vinod Koul <vkoul@...nel.org>,
        Allison Randal <allison@...utok.net>,
        Alexios Zavras <alexios.zavras@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Alexander.Barabash@...l.com" <Alexander.Barabash@...l.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] dmaengine: ioat: adding missed issue_pending to
 timeout handler



On 4/22/2020 4:22 AM, leonid.ravich@...l.com wrote:
> From: Leonid Ravich <Leonid.Ravich@....com>
> 
> completion timeout might trigger unnesesery DMA engine hw reboot
> in case of missed issue_pending() .

Just curious, are you hitting a use case where this is happening? And 
what's causing the completion timeout?

> 
> Signed-off-by: Leonid Ravich <Leonid.Ravich@....com>
> ---
>   drivers/dma/ioat/dma.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/dma/ioat/dma.c b/drivers/dma/ioat/dma.c
> index 55a8cf1..2ab07a3 100644
> --- a/drivers/dma/ioat/dma.c
> +++ b/drivers/dma/ioat/dma.c
> @@ -955,6 +955,13 @@ void ioat_timer_event(struct timer_list *t)
>   		goto unlock_out;
>   	}
>   
> +	/* handle missed issue pending case */
> +	if (ioat_ring_pending(ioat_chan)) {
> +		spin_lock_bh(&ioat_chan->prep_lock);
> +		__ioat_issue_pending(ioat_chan);
> +		spin_unlock_bh(&ioat_chan->prep_lock);
> +	}
> +
>   	set_bit(IOAT_COMPLETION_ACK, &ioat_chan->state);
>   	mod_timer(&ioat_chan->timer, jiffies + COMPLETION_TIMEOUT);
>   unlock_out:
>