Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 28 Aug 2013 11:27:38 +0530 | From | Vinod Koul <> | Subject | Re: [PATCH resend] dma: pl330: Fix handling of TERMINATE_ALL while processing completed descriptors |
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On Tue, Aug 27, 2013 at 08:34:05PM +0200, Lars-Peter Clausen wrote: > The pl330 DMA driver is broken in regard to handling a terminate all request > while it is processing the list of completed descriptors. This is most visible > when calling dmaengine_terminate_all() from within the descriptors callback for > cyclic transfers. In this case the TERMINATE_ALL transfer will clear the > work_list and stop the transfer. But after all callbacks for all completed > descriptors have been handled the descriptors will be re-enqueued into the (now > empty) work_list. So the next time dma_async_issue_pending() is called for the > channel these descriptors will be transferred again which will cause data > corruption. Similar issues can occur if dmaengine_terminate_all() is not called > from within the descriptor callback but runs on a different CPU at the same time > as the completed descriptor list is processed. > > This patch introduces a new per channel list which will hold the completed > descriptors. While processing the list the channel's lock will be held to avoid > racing against dmaengine_terminate_all(). The lock will be released when calling > the descriptors callback though. Since the list of completed descriptors might > be modified (e.g. by calling dmaengine_terminate_all() from the callback) we can > not use the normal list iterator macros. Instead we'll need to check for each > loop iteration again if there are still items in the list. The drivers > TERMINATE_ALL implementation is updated to move descriptors from both the > work_list as well the new completed_list back to the descriptor pool. This makes > sure that none of the descripts finds its way back into the work list and also > that we do not call any futher complete callbacks after > dmaengine_terminate_all() has been called.
Applied, thanks
~Vinod
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