Re: [PATCH v4 21/25] dmaengine: sdxi: Provide context start and stop APIs

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

On Tue, Nov 03, 2026 at 08:50:02PM -0600, Nathan Lynch wrote:
> Implement client context start and stop by submitting administrative
> descriptors. Starting waits for the start descriptor to finish; stopping
> submits stop followed by synchronization and waits for the latter.
>
> Use the administrative reservation and polling helpers to claim status
> blocks before reserving descriptors, release consumed results, and retain
> timed-out blocks until context teardown. Expose these operations through
> struct sdxi_cxt for clients such as the DMAengine provider.
>
> Co-developed-by: Wei Huang <wei.huang2@amd.com>
> Signed-off-by: Wei Huang <wei.huang2@amd.com>
> Signed-off-by: Nathan Lynch <nathan.lynch@amd.com>
> ---

Reviewed-by: Frank Li <Frank.Li@nxp.com>

>  drivers/dma/sdxi/context.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++
>  drivers/dma/sdxi/context.h |  3 +++
>  2 files changed, 64 insertions(+)
>
> diff --git a/drivers/dma/sdxi/context.c b/drivers/dma/sdxi/context.c
> index 5ca99ac8080c..0979fa35346b 100644
> --- a/drivers/dma/sdxi/context.c
> +++ b/drivers/dma/sdxi/context.c
> @@ -364,6 +364,67 @@ int sdxi_admin_cxt_init(struct sdxi_dev *sdxi)
>  	return devm_add_action_or_reset(sdxi->dev, free_admin_cxt, sdxi);
>  }
>
> +int sdxi_start_cxt(struct sdxi_cxt *cxt)
> +{
> +	struct sdxi_cxt *adm = to_admin_cxt(cxt);
> +	struct sdxi_ring_resv resv;
> +	struct sdxi_completion comp;
> +	struct sdxi_slot start;
> +	int err;
> +
> +	might_sleep();
> +
> +	/* Administrative context activation is controlled by the function state. */
> +	if (WARN_ON(adm == cxt))
> +		return -EINVAL;
> +
> +	err = sdxi_cxt_reserve(adm, 1, &resv, &comp);
> +	if (err)
> +		return err;
> +
> +	start = sdxi_ring_resv_slot(&resv, 0);
> +	sdxi_encode_cxt_start(sdxi_slot_desc(start), &(const struct sdxi_cxt_start) {
> +			.range = sdxi_cxt_range_single(cxt->id),
> +		});
> +	sdxi_cxt_submit(adm, start, &comp, SDXI_CXT_SUBMIT_KICK);
> +
> +	return sdxi_cxt_poll_completion(adm, &comp);
> +}
> +
> +void sdxi_stop_cxt(struct sdxi_cxt *cxt)
> +{
> +	struct sdxi_cxt *adm = to_admin_cxt(cxt);
> +	struct sdxi_slot stop, sync;
> +	struct sdxi_ring_resv resv;
> +	struct sdxi_completion comp;
> +	int err;
> +
> +	might_sleep();
> +
> +	/* Administrative context stopping is controlled by the function state. */
> +	if (WARN_ON(adm == cxt))
> +		return;
> +
> +	err = sdxi_cxt_reserve(adm, 2, &resv, &comp);
> +	if (WARN_ON_ONCE(err))
> +		return;
> +
> +	stop = sdxi_ring_resv_slot(&resv, 0);
> +	sync = sdxi_ring_resv_slot(&resv, 1);
> +
> +	sdxi_encode_cxt_stop(sdxi_slot_desc(stop), &(const struct sdxi_cxt_stop) {
> +			.range = sdxi_cxt_range_single(cxt->id),
> +		});
> +	sdxi_encode_sync(sdxi_slot_desc(sync), &(const struct sdxi_sync) {
> +			.filter = SDXI_SYNC_FLT_STOP,
> +			.range = sdxi_cxt_range_single(cxt->id),
> +		});
> +	sdxi_cxt_submit(adm, stop, NULL, 0);
> +	sdxi_cxt_submit(adm, sync, &comp, SDXI_CXT_SUBMIT_KICK);
> +
> +	WARN_ON(sdxi_cxt_poll_completion(adm, &comp));
> +}
> +
>  /*
>   * Temporary owner for context id until it can be assigned to a
>   * context object; enables scope-based cleanup.
> diff --git a/drivers/dma/sdxi/context.h b/drivers/dma/sdxi/context.h
> index 71eef2c6243b..acf41709c4de 100644
> --- a/drivers/dma/sdxi/context.h
> +++ b/drivers/dma/sdxi/context.h
> @@ -60,6 +60,9 @@ struct sdxi_cxt *sdxi_cxt_new(struct sdxi_dev *sdxi);
>  int sdxi_cxt_exit(struct sdxi_cxt *cxt);
>  void sdxi_client_cxts_exit(struct sdxi_dev *sdxi);
>
> +int sdxi_start_cxt(struct sdxi_cxt *cxt);
> +void sdxi_stop_cxt(struct sdxi_cxt *cxt);
> +
>  enum sdxi_submit_flags {
>  	SDXI_CXT_SUBMIT_KICK  = BIT(0),
>  	SDXI_CXT_SUBMIT_FENCE = BIT(1),
>
> --
> 2.56.0
>