Re: [PATCH v7 05/10] dmaengine: dw-edma: Add channel delegation helpers

[Frank Li]

On Thu, Aug 13, 2026 at 03:37:52PM +0900, Koichiro Den wrote:
> Endpoint functions that expose endpoint-local DesignWare eDMA channels
> to a remote host need to reserve exact hardware channels and hand
> interrupt ownership to the remote side before publishing the channels.
>
> Add DW eDMA-specific helpers that validate an idle, already reserved
> channel and switch it to remote interrupt routing. The matching reclaim
> helper can quiesce the channel while it is still remote-routed, then
> restores the channel's default routing. The dmaengine channel reservation
> remains with the caller.
>
> Reclaim is best-effort because its callers cannot abort teardown. Report
> a quiesce failure locally, but always restore the default routing.
>
> Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>
> ---
> Changes in v7:
>   - Leave dmaengine channel selection and lifetime management to the
>     endpoint function, per discussion with Frank on v6 patch 4.
>
>  drivers/dma/dw-edma/dw-edma-core.c | 39 ++++++++++++++++++++++++++++++
>  include/linux/dma/edma.h           | 11 +++++++++
>  2 files changed, 50 insertions(+)

After change to static id, needn't these private API. You can get expected
channel and use dma_slave_config to config use DW_EDMA_CH_IRQ_REMOTE

Frank

> diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
> index d214df55da3c..1582ecfc2965 100644
> --- a/drivers/dma/dw-edma/dw-edma-core.c
> +++ b/drivers/dma/dw-edma/dw-edma-core.c
> @@ -1303,6 +1303,45 @@ int dw_edma_remove(struct dw_edma_chip *chip)
>  }
>  EXPORT_SYMBOL_GPL(dw_edma_remove);
>
> +int dw_edma_delegate_chan(struct dma_chan *dchan)
> +{
> +	struct dw_edma_chan *chan = dchan2dw_edma_chan(dchan);
> +	int ret = 0;
> +
> +	if (!(chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL))
> +		return -EINVAL;
> +
> +	guard(spinlock_irqsave)(&chan->vc.lock);
> +
> +	if (chan->configured || chan->status != EDMA_ST_IDLE ||
> +	    chan->request != EDMA_REQ_NONE)
> +		ret = -EBUSY;
> +	else
> +		chan->irq_mode = DW_EDMA_CH_IRQ_REMOTE;
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(dw_edma_delegate_chan);
> +
> +void dw_edma_reclaim_chan(struct dma_chan *dchan, bool quiesce)
> +{
> +	struct dw_edma_chan *chan;
> +
> +	if (!dchan)
> +		return;
> +
> +	chan = dchan2dw_edma_chan(dchan);
> +	if (quiesce && dw_edma_core_ch_quiesce(chan))
> +		dev_warn(chan->dw->chip->dev,
> +			 "failed to quiesce delegated %s channel %u\n",
> +			 chan->dir == EDMA_DIR_WRITE ? "write" : "read",
> +			 chan->id);
> +
> +	scoped_guard(spinlock_irqsave, &chan->vc.lock)
> +		chan->irq_mode = dw_edma_get_default_irq_mode(chan);
> +}
> +EXPORT_SYMBOL_GPL(dw_edma_reclaim_chan);
> +
>  MODULE_LICENSE("GPL v2");
>  MODULE_DESCRIPTION("Synopsys DesignWare eDMA controller core driver");
>  MODULE_AUTHOR("Gustavo Pimentel <gustavo.pimentel@xxxxxxxxxxxx>");
> diff --git a/include/linux/dma/edma.h b/include/linux/dma/edma.h
> index 3c8e2ef9dee0..61ebb808981e 100644
> --- a/include/linux/dma/edma.h
> +++ b/include/linux/dma/edma.h
> @@ -153,6 +153,8 @@ struct dw_edma_chip {
>  #if IS_REACHABLE(CONFIG_DW_EDMA)
>  int dw_edma_probe(struct dw_edma_chip *chip);
>  int dw_edma_remove(struct dw_edma_chip *chip);
> +int dw_edma_delegate_chan(struct dma_chan *chan);
> +void dw_edma_reclaim_chan(struct dma_chan *chan, bool quiesce);
>  #else
>  static inline int dw_edma_probe(struct dw_edma_chip *chip)
>  {
> @@ -163,6 +165,15 @@ static inline int dw_edma_remove(struct dw_edma_chip *chip)
>  {
>  	return 0;
>  }
> +
> +static inline int dw_edma_delegate_chan(struct dma_chan *chan)
> +{
> +	return -ENODEV;
> +}
> +
> +static inline void dw_edma_reclaim_chan(struct dma_chan *chan, bool quiesce)
> +{
> +}
>  #endif /* CONFIG_DW_EDMA */
>
>  #endif /* _DW_EDMA_H */
> --
> 2.51.0
>