linux-kernel - Re: [PATCH 2/3] dmaengine: at_xdmac: enhance channel errors handling in tasklet

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Message-ID: <20190211115834.GS4296@vkoul-mobl>
Date:   Mon, 11 Feb 2019 17:28:34 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Nicolas Ferre <nicolas.ferre@...rochip.com>
Cc:     Ludovic Desroches <ludovic.desroches@...rochip.com>,
        linux-arm-kernel@...ts.infradead.org, dmaengine@...r.kernel.org,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] dmaengine: at_xdmac: enhance channel errors handling
 in tasklet

On 05-02-19, 12:03, Nicolas Ferre wrote:
> Complement the identification of errors with stoping the channel and
> dumping the descriptor that led to the error case.
> 
> Signed-off-by: Nicolas Ferre <nicolas.ferre@...rochip.com>
> ---
>  drivers/dma/at_xdmac.c | 43 ++++++++++++++++++++++++++++++++++++------
>  1 file changed, 37 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
> index 37a269420435..ec7a29d8e448 100644
> --- a/drivers/dma/at_xdmac.c
> +++ b/drivers/dma/at_xdmac.c
> @@ -1575,6 +1575,41 @@ static void at_xdmac_handle_cyclic(struct at_xdmac_chan *atchan)
>  		dmaengine_desc_get_callback_invoke(txd, NULL);
>  }
>  
> +static void at_xdmac_handle_error(struct at_xdmac_chan *atchan)
> +{
> +	struct at_xdmac		*atxdmac = to_at_xdmac(atchan->chan.device);
> +	struct at_xdmac_desc	*bad_desc;
> +
> +	/*
> +	 * The descriptor currently at the head of the active list is
> +	 * broked. Since we don't have any way to report errors, we'll

You meant borked or broken... 

> +	 * just have to scream loudly and try to carry on.

should we carry on or abort..?

> +	 */
> +	if (atchan->irq_status & AT_XDMAC_CIS_RBEIS)
> +		dev_err(chan2dev(&atchan->chan), "read bus error!!!");
> +	if (atchan->irq_status & AT_XDMAC_CIS_WBEIS)
> +		dev_err(chan2dev(&atchan->chan), "write bus error!!!");
> +	if (atchan->irq_status & AT_XDMAC_CIS_ROIS)
> +		dev_err(chan2dev(&atchan->chan), "request overflow error!!!");
> +
> +	spin_lock_bh(&atchan->lock);
> +	/* Channel must be disabled first as it's not done automatically */
> +	at_xdmac_write(atxdmac, AT_XDMAC_GD, atchan->mask);
> +	while (at_xdmac_read(atxdmac, AT_XDMAC_GS) & atchan->mask)
> +		cpu_relax();
> +	bad_desc = list_first_entry(&atchan->xfers_list,
> +				    struct at_xdmac_desc,
> +				    xfer_node);
> +	spin_unlock_bh(&atchan->lock);
> +	/* Print bad descriptor's details if needed */

Well this is not great to look and read at, please do consider adding
empty line before comments or logical blocks..

> +	dev_dbg(chan2dev(&atchan->chan),
> +		 "%s: lld: mbr_sa=%pad, mbr_da=%pad, mbr_ubc=0x%08x\n",
> +		 __func__, &bad_desc->lld.mbr_sa, &bad_desc->lld.mbr_da,
> +		 bad_desc->lld.mbr_ubc);

not dev_err?

> +
> +	/* Then continue with usual descriptor management */
> +}
> +
>  static void at_xdmac_tasklet(unsigned long data)
>  {
>  	struct at_xdmac_chan	*atchan = (struct at_xdmac_chan *)data;
> @@ -1594,12 +1629,8 @@ static void at_xdmac_tasklet(unsigned long data)
>  		   || (atchan->irq_status & error_mask)) {
>  		struct dma_async_tx_descriptor  *txd;
>  
> -		if (atchan->irq_status & AT_XDMAC_CIS_RBEIS)
> -			dev_err(chan2dev(&atchan->chan), "read bus error!!!");
> -		if (atchan->irq_status & AT_XDMAC_CIS_WBEIS)
> -			dev_err(chan2dev(&atchan->chan), "write bus error!!!");
> -		if (atchan->irq_status & AT_XDMAC_CIS_ROIS)
> -			dev_err(chan2dev(&atchan->chan), "request overflow error!!!");
> +		if (atchan->irq_status & error_mask)
> +			at_xdmac_handle_error(atchan);
>  
>  		spin_lock(&atchan->lock);
>  		desc = list_first_entry(&atchan->xfers_list,
> -- 
> 2.17.1

-- 
~Vinod