Re: [PATCH v4 04/12] dmaengine: switchtec-dma: halt channel on alloc_chan_resources error

[Frank Li <Frank.li@oss.nxp.com>]

On Tue, Jul 28, 2026 at 11:15:15AM -0600, Logan Gunthorpe wrote:
> The error-unwind path called disable_channel() before freeing the
> descriptor rings, but that only clears the enable bit with an
> unflushed write -- it doesn't halt the channel or clear its DMA base
> address registers. If unhalt_channel() timed out, the channel's actual
> state is unknown at that point, so nothing guarantees the hardware
> isn't still touching the rings when they're freed.
>
> Call switchtec_dma_chan_stop() first, matching what
> switchtec_dma_free_chan_resources() already does before freeing
> descriptors on the normal teardown path: it synchronously halts the
> channel and zeroes the DMA base registers. If the halt itself can't be
> confirmed, skip freeing the descriptor rings (leaking them instead).
>
> Fixes: 30eba9df76ad ("dmaengine: switchtec-dma: Implement hardware initialization and cleanup")
> Reported-by: Sashiko <sashiko-bot@kernel.org>
> Link: https://lore.kernel.org/dmaengine/20260717223647.F0A051F000E9@smtp.kernel.org
> Link: https://lore.kernel.org/dmaengine/20260727185101.D221C1F000E9@smtp.kernel.org
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> ---

Like patch4, leave it as it now utile we found go method.

You'd better post new patches, which just include my review-by tags, so
vnod can handle easily.

Then continue work on two sashiko report unlikely happen problem.

Frank

>  drivers/dma/switchtec_dma.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/dma/switchtec_dma.c b/drivers/dma/switchtec_dma.c
> index cbbc9ad08247..25b988e9b4af 100644
> --- a/drivers/dma/switchtec_dma.c
> +++ b/drivers/dma/switchtec_dma.c
> @@ -1047,6 +1047,10 @@ static int switchtec_dma_alloc_chan_resources(struct dma_chan *chan)
>  	swdma_chan->comp_ring_active = false;
>  	spin_unlock_bh(&swdma_chan->complete_lock);
>  err_disable_channel:
> +	if (switchtec_dma_chan_stop(swdma_chan)) {
> +		disable_channel(swdma_chan);
> +		return rc;
> +	}
>  	disable_channel(swdma_chan);
>  err_free_desc:
>  	switchtec_dma_free_desc(swdma_chan);
> --
> 2.47.3
>