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Re: [PATCH 2/7] dmaengine: omap-dma: Complete the cookie first on transfer completion

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On 07/18/16 13:34, Russell King - ARM Linux wrote:
> On Thu, Jul 14, 2016 at 03:42:37PM +0300, Peter Ujfalusi wrote:
>> Before looking for the next descriptor to start, complete the just finished
>> cookie.
> 
> This change will reduce performance as we no longer have an overlap
> between the next request starting to be dealt with in the hardware
> vs the previous request being completed.

vchan_cookie_complete() will only mark the cookie completed, adds the vd to
the desc_completed list (it was deleted from desc_issued list when it was
started by omap_dma_start_desc) and schedule the tasklet to deal with the real
completion later.
Marking the just finished descriptor/cookie done first then looking for
possible descriptors in the queue to start feels like a better sequence.

After a quick grep in the kernel source: only omap-dma.c was starting the next
transfer before marking the current completed descriptor/cookie done.

> Your commit log doesn't
> say _why_ the change is being made, it merely tells us what the
> patch is doing, which we can see already.
> 
> Please describe changes a little better.
> 


-- 
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[PATCH 0/7] dmaengine:omap-dma: Linked List transfer for slave_sg Peter Ujfalusi <peter.ujfalusi@ti.com> - 2016-07-14 14:50 +0200
  [PATCH 1/7] dmaengine: omap-dma: Simplify omap_dma_start_sg parameter list Peter Ujfalusi <peter.ujfalusi@ti.com> - 2016-07-14 14:50 +0200
  [PATCH 7/7] dmaengine: omap-dma: Support for LinkedList transfer of slave_sg Peter Ujfalusi <peter.ujfalusi@ti.com> - 2016-07-14 14:50 +0200
    Re: [PATCH 7/7] dmaengine: omap-dma: Support for LinkedList transfer  of slave_sg Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-07-18 12:50 +0200
      Re: [PATCH 7/7] dmaengine: omap-dma: Support for LinkedList transfer  of slave_sg Peter Ujfalusi <peter.ujfalusi@ti.com> - 2016-07-18 13:20 +0200
  [PATCH 2/7] dmaengine: omap-dma: Complete the cookie first on transfer completion Peter Ujfalusi <peter.ujfalusi@ti.com> - 2016-07-14 14:50 +0200
    Re: [PATCH 2/7] dmaengine: omap-dma: Complete the cookie first on  transfer completion Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-07-18 12:40 +0200
      Re: [PATCH 2/7] dmaengine: omap-dma: Complete the cookie first on  transfer completion Peter Ujfalusi <peter.ujfalusi@ti.com> - 2016-07-19 14:40 +0200
        Re: [PATCH 2/7] dmaengine: omap-dma: Complete the cookie first on  transfer completion Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-07-19 18:30 +0200
          Re: [PATCH 2/7] dmaengine: omap-dma: Complete the cookie first on  transfer completion Peter Ujfalusi <peter.ujfalusi@ti.com> - 2016-07-19 21:30 +0200
          Re: [PATCH 2/7] dmaengine: omap-dma: Complete the cookie first on  transfer completion Vinod Koul <vinod.koul@intel.com> - 2016-07-24 09:40 +0200
        Re: [PATCH 2/7] dmaengine: omap-dma: Complete the cookie first on transfer completion Robert Jarzmik <robert.jarzmik@free.fr> - 2016-07-20 08:30 +0200
          Re: [PATCH 2/7] dmaengine: omap-dma: Complete the cookie first on  transfer completion Peter Ujfalusi <peter.ujfalusi@ti.com> - 2016-07-21 11:40 +0200
          Re: [PATCH 2/7] dmaengine: omap-dma: Complete the cookie first on  transfer completion Peter Ujfalusi <peter.ujfalusi@ti.com> - 2016-07-21 11:40 +0200
            Re: [PATCH 2/7] dmaengine: omap-dma: Complete the cookie first on  transfer completion Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-07-21 11:50 +0200
              Re: [PATCH 2/7] dmaengine: omap-dma: Complete the cookie first on  transfer completion Peter Ujfalusi <peter.ujfalusi@ti.com> - 2016-07-22 13:10 +0200
  [PATCH 4/7] dmaengine: omap-dma: Dynamically allocate memory for lch_map Peter Ujfalusi <peter.ujfalusi@ti.com> - 2016-07-14 14:50 +0200
  [PATCH 6/7] dmaengine: omap-dma: Use pointer to omap_sg in slave_sg setup's loop Peter Ujfalusi <peter.ujfalusi@ti.com> - 2016-07-14 14:50 +0200
  Re: [PATCH 0/7] dmaengine:omap-dma: Linked List transfer for slave_sg Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-07-18 12:40 +0200
    Re: [PATCH 0/7] dmaengine:omap-dma: Linked List transfer for slave_sg Peter Ujfalusi <peter.ujfalusi@ti.com> - 2016-07-18 14:10 +0200
      Re: [PATCH 0/7] dmaengine:omap-dma: Linked List transfer for slave_sg Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-07-18 14:30 +0200
        Re: [PATCH 0/7] dmaengine:omap-dma: Linked List transfer for slave_sg Peter Ujfalusi <peter.ujfalusi@ti.com> - 2016-07-18 14:40 +0200

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