Re: [PATCH v3 4/4] 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: stale chan->cyclic across alloc,
  error, and prep failure
--

commit 9842b102714b426daae54ae8ebc997ef84ba1d86
Author: James Hilliard <james.hilliard1@gmail.com>

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

This commit tracks pending channel suspend requests, active descriptors, and
deferred cyclic restarts so pause and resume operations do not lose
hardware suspend acknowledgments or race with transfer completion.

> 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 bb305ab94d02b..6f15fcb790a80 100644
> --- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> +++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c

[ ... ]

> @@ -543,6 +548,10 @@ static int dma_chan_alloc_chan_resources(struct dma_chan *dchan)
>  		pm_runtime_put(chan->chip->dev);
>  		return -ENOMEM;
>  	}
> +	chan->desc = NULL;
> +	chan->pause_requested = false;
> +	chan->is_paused = false;
> +	chan->cyclic_restart = false;
>  	dev_vdbg(dmaengine_chan_dev(dchan), "%s: allocating\n", axi_chan_name(chan));
>  
>  	return 0;
> @@ -1087,6 +1096,8 @@ static noinline void axi_chan_handle_err(struct axi_dma_chan *chan, u32 status)
>  	vchan_cookie_complete(vd);
>  
>  	/* Try to restart the controller */
> +	chan->desc = NULL;
> +	chan->cyclic_restart = false;
>  	axi_chan_start_first_queued(chan);
>  
>  out:

[Severity: Medium]
Should dma_chan_alloc_chan_resources() and axi_chan_handle_err() also reset
chan->cyclic to false?

chan->cyclic is only cleared on a successful dma_chan_terminate_all(), and
neither dw_axi_dma_chan_prep_slave_sg() nor dma_chan_prep_dma_memcpy()
resets it.  If a prior dma_chan_terminate_all() timed out or was skipped
before channel release, or if a cyclic transfer fails in
axi_chan_handle_err(), chan->cyclic stays true.  Any subsequent non-cyclic
transfer then takes the cyclic branch in axi_chan_block_xfer_complete(),
which skips vchan_cookie_complete() and clearing chan->desc, leaving the
completed descriptor on vc.desc_issued, blocking further queued descriptors,
and re-enabling the hardware channel.

Similarly, dw_axi_dma_chan_prep_cyclic() sets chan->cyclic = true before the
dw_axi_dma_set_hw_desc() loop and leaves it set if the err_desc_get error
path is taken.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261110-submit-dw-axi-dma-stop-pause-v1-v3-0-35fdfba8b61d@gmail.com?part=4