[PATCH v1 1/5] dma: Add QorIQ qDMA engine driver support

Russell King - ARM Linux linux at armlinux.org.uk
Thu Aug 18 02:16:03 PDT 2016

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."

RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
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