linux-kernel - RE: [PATCH v1 1/5] dma: Add QorIQ qDMA engine driver support

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Message-ID: <DB6PR0401MB240759E8AC4DEB23EBC1159389EA0@DB6PR0401MB2407.eurprd04.prod.outlook.com>
Date:   Wed, 24 Aug 2016 03:39:11 +0000
From:   Yao Yuan <yao.yuan@....com>
To:     Russell King - ARM Linux <linux@...linux.org.uk>,
        Yuan Yao <yao.yuan@...escale.com>
CC:     "vinod.koul@...el.com" <vinod.koul@...el.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        Yang-Leo Li <leoyang.li@....com>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH v1 1/5] dma: Add QorIQ qDMA engine driver support

On Thu, Aug 18, 2016 at 05:16 PM +0800, Russell King wrote:
> On Thu, Aug 18, 2016 at 02:38:44PM +0800, Yuan Yao wrote:
> > +			spin_lock(&fsl_comp->qchan->vchan.lock);
> > +			if (status == DMA_COMPLETE)
> > +				vchan_cookie_complete(&fsl_comp->vdesc);
> > +			fsl_comp->qchan->status = status;
> 
> This is buggy - if the DMA has finished processing it, even if it finished in error, it
> must _complete_ the transaction.  Completion is not the same as being
> successful - it means that the DMA is no longer processing the cookie.
> 
> The issue here is that when the _following_ transaction completes successfully,
> _this_ transaction will effectively be marked as complete due to the way the
> cookie system works.
> 
> So... to get this straight - "completion" means "I have finished processing this
> transaction".  It does not mean "I successfully processed this transaction
> without any errors."
> 

Thanks for your review.
So you mean that I should call vchan_cookie_complete no matter whether the error issue in QDMA?
I have some random DMA error test case, it seems work will.