Re: [PATCH v4 5/5] dmaengine: dw-axi-dmac: preserve pending pause requests

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Medium] dmaengine: dw-axi-dmac: cyclic completion bypasses suspend
  cleanup
--

commit 42cf728bc72837bdd6aafccd6828bd4c191d4963
Author: James Hilliard <james.hilliard1@gmail.com>

dmaengine: dw-axi-dmac: preserve pending pause requests

This commit tracks pending pause requests separately from hardware suspend
acknowledgment and defers restarting cyclic or queued descriptors while a
pause is requested.

> diff --git a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> index 1a53fbc951a91..70ff0c5006231 100644
> --- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> +++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c

[ ... ]

> @@ -1134,11 +1145,18 @@ static void axi_chan_block_xfer_complete(struct axi_dma_chan *chan)
>  			}
>  		}
>  
> -		axi_chan_enable(chan);
> +		if (chan->pause_requested) {
> +			chan->is_paused = true;
> +			chan->cyclic_restart = true;
> +		} else {
> +			axi_chan_enable(chan);
> +		}
>  	} else {

[Severity: Medium]
Does setting chan->is_paused here skip cleaning up an unacknowledged
hardware suspend request when a cyclic block completes after
dma_chan_pause() times out?

If dma_chan_pause() writes the channel suspend request and times out in
axi_chan_wait_for_suspend(), chan->pause_requested remains true while the
hardware suspend request stays pending.  When the in-flight cyclic block
then finishes, axi_chan_block_xfer_complete() sets chan->is_paused = true
without calling axi_chan_disable() or clearing DWAXIDMAC_IRQ_SUSPENDED.  A
later dma_chan_pause() retry or dma_chan_resume() call sees chan->is_paused
and returns early from axi_chan_wait_for_suspend(), bypassing the
axi_chan_disable() call in axi_chan_is_suspended() that clears an
unacknowledged suspend request on a completed transfer.

Leaving chan->is_paused false here (or calling axi_chan_disable() and
clearing DWAXIDMAC_IRQ_SUSPENDED before setting chan->is_paused) would
ensure the pending hardware suspend state is cleaned up before the channel
is re-enabled on resume.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261112-submit-dw-axi-dma-stop-pause-v1-v4-0-3ebc24b243db@gmail.com?part=5