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

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Message-ID: <1cdc51b6-3b0b-ee17-855a-ebd3896059ba@microchip.com>
Date:   Wed, 3 Apr 2019 10:05:00 +0000
From:   <Nicolas.Ferre@...rochip.com>
To:     <vkoul@...nel.org>
CC:     <Ludovic.Desroches@...rochip.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <dmaengine@...r.kernel.org>, <alexandre.belloni@...tlin.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] dmaengine: at_xdmac: enhance channel errors handling
 in tasklet

Vinod,

Thanks for your review, I'm preparing v2.

On 11/02/2019 at 12:58, Vinod Koul wrote:
> 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...

Broken

> 
>> +	 * just have to scream loudly and try to carry on.
> 
> should we carry on or abort..?

Changed in:

  * just have to scream loudly and try to continue with other
  * descriptors queued (if any).

>> +	 */
>> +	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..

True, indeed.

>> +	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?

Well, we have the dev_err at the beginning of the function, I think it's 
enough: this is really debugging information that needs to be activated 
to track the DMA configuration bug: it's not meant for production.

>> +
>> +	/* 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
> 


-- 
Nicolas Ferre