Re: [PATCH v2 04/19] dmaengine: dw-edma: Make DMA link list work as a circular buffer

On Thu, Jul 23, 2026 at 09:07:05AM +0000, [email protected] wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [High] Ring buffer capacity is permanently leaked on error and termination paths because `ll_end` is not advanced.
> --
>
> --- Patch [4]: [PATCH v2 04/19] dmaengine: dw-edma: Make DMA link list work as a circular buffer ---
> commit 2d5b6554b58830487f70a13eab5e1ac3de304658
> Author: Frank Li <[email protected]>
>
> dmaengine: dw-edma: Make DMA link list work as a circular buffer
>
> This commit updates the driver to use the DMA linked list as a circular
> ring buffer. It appends entries at ll_head with the current cycle bit and
> reserves the final entry to link back to the start.
>
> > diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
> > --- a/drivers/dma/dw-edma/dw-edma-core.c
> > +++ b/drivers/dma/dw-edma/dw-edma-core.c
>
> [ ... ]
>
> > @@ -645,6 +687,8 @@ static void dw_edma_done_interrupt(struct dw_edma_chan *chan)
> >  							    DMA_TRANS_NOERROR);
> >  				list_del(&vd->node);
> >  				vchan_cookie_complete(vd);
> > +				if (!chan->non_ll)
> > +					chan->ll_end = chan->ll_head;
> >  			}
> >
> >  			if (chan->request == EDMA_REQ_PAUSE) {
>
> [Severity: High]
> Does this leak ring capacity when descriptors are aborted or terminated?
>
> This block successfully reclaims ring capacity on successful completion by
> advancing chan->ll_end. However, if a client driver queues transfers and
> then aborts them (for example, via dmaengine_terminate_all() or during an
> abort interrupt), the descriptors are removed from the list but chan->ll_end
> does not appear to be updated to reflect the aborted descriptors.
>
> Since chan->ll_valid remains true after a termination, subsequent transfers
> will bypass the dw_edma_core_reset_ll() ring reset logic and continue
> appending to the un-reclaimed ring.

Make sense. Need change at these abnormal case.

Frank
>
> Will this eventually cause dw_edma_core_get_free_num() to permanently return
> 0 and deadlock the channel once the un-reclaimed slots exhaust the ring?
>
> --
> Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=4