Re: [PATCH v2 2/3] dmaengine: dw-edma: Configure remote interrupt routing

[Frank Li]

On Sat, Aug 29, 2026 at 01:36:10AM +0900, Koichiro Den wrote:
> An endpoint function can reserve an endpoint-local channel while the RC
> programs it through an exposed register window. Such a channel must route
> interrupts remotely and ignore them on the endpoint.
>
> Use dma_slave_config to set enum dw_edma_ch_irq_mode on idle channels of a
> local eDMA-compatible instance. Synchronizing a remote-routed channel
> quiesces the hardware, after which the caller can restore its routing and
> release it.
>
> The eDMA quiesce may stop a complete direction. The caller must own every
> channel in that direction and stop remote programming first.
>
> Suggested-by: Frank Li <Frank.Li@xxxxxxx>
> Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>
> ---
> Changes in v2:
>   - Rework the channel routing from PCI DMA EPF v7 patches 5 and 6.
>     https://lore.kernel.org/r/20260813063757.3131865-6-den@xxxxxxxxxxxxx/
>     https://lore.kernel.org/r/20260813063757.3131865-7-den@xxxxxxxxxxxxx/
>   - Use dma_slave_config instead of private delegation helpers. (Frank)
>     https://lore.kernel.org/r/ao2nHoCwfTEEiFSr@SMW015318/
>
>  drivers/dma/dw-edma/dw-edma-core.c | 51 +++++++++++++++++++++++++++---
>  include/linux/dma/edma.h           |  6 ++++
>  2 files changed, 52 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
> index a678c70a78fe..a8c6bd508fcd 100644
> --- a/drivers/dma/dw-edma/dw-edma-core.c
> +++ b/drivers/dma/dw-edma/dw-edma-core.c
> @@ -177,6 +177,30 @@ dw_edma_get_default_irq_mode(struct dw_edma_chan *chan)
>  						  DW_EDMA_CH_IRQ_REMOTE;
>  }
>
> +static int dw_edma_device_config_irq_mode(struct dw_edma_chan *chan,
> +					  struct dma_slave_config *config)
> +{
> +	enum dw_edma_ch_irq_mode mode;
> +
> +	if (!(chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL) ||
> +	    config->peripheral_size != sizeof(mode))
> +		return -EINVAL;
> +
> +	mode = *(enum dw_edma_ch_irq_mode *)config->peripheral_config;

existing code use peripheral_config indicate non_ll mode, is it compatible
with irq mode?

Frank

> +	if (mode != DW_EDMA_CH_IRQ_LOCAL && mode != DW_EDMA_CH_IRQ_REMOTE)
> +		return -EINVAL;
> +
> +	guard(spinlock_irqsave)(&chan->vc.lock);
> +
> +	if (chan->configured || chan->status != EDMA_ST_IDLE ||
> +	    chan->request != EDMA_REQ_NONE)
> +		return -EBUSY;
> +
> +	chan->irq_mode = mode;
> +
> +	return 0;
> +}
> +
>  static int dw_edma_device_config(struct dma_chan *dchan,
>  				 struct dma_slave_config *config)
>  {
> @@ -184,6 +208,10 @@ static int dw_edma_device_config(struct dma_chan *dchan,
>  	bool cfg_non_ll;
>  	int non_ll = 0;
>
> +	if (chan->dw->chip->mf != EDMA_MF_HDMA_NATIVE &&
> +	    config->peripheral_config)
> +		return dw_edma_device_config_irq_mode(chan, config);
> +
>  	chan->non_ll = false;
>  	if (chan->dw->chip->mf == EDMA_MF_HDMA_NATIVE) {
>  		if (config->peripheral_config &&
> @@ -213,10 +241,6 @@ static int dw_edma_device_config(struct dma_chan *dchan,
>
>  		if (cfg_non_ll || non_ll)
>  			chan->non_ll = true;
> -	} else if (config->peripheral_config) {
> -		dev_err(dchan->device->dev,
> -			"peripheral config param applicable only for HDMA\n");
> -		return -EINVAL;
>  	}
>
>  	memcpy(&chan->config, config, sizeof(*config));
> @@ -893,6 +917,17 @@ static void dw_edma_wait_termination(struct dma_chan *dchan)
>  static void dw_edma_device_synchronize(struct dma_chan *dchan)
>  {
>  	struct dw_edma_chan *chan = dchan2dw_edma_chan(dchan);
> +	bool remote;
> +
> +	scoped_guard(spinlock_irqsave, &chan->vc.lock)
> +		remote = chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL &&
> +			 chan->irq_mode == DW_EDMA_CH_IRQ_REMOTE;
> +
> +	if (remote && dw_edma_core_ch_quiesce(chan))
> +		dev_warn(chan->dw->chip->dev,
> +			 "failed to quiesce remote-routed %s channel %u\n",
> +			 chan->dir == EDMA_DIR_WRITE ? "write" : "read",
> +			 chan->id);
>
>  	dw_edma_wait_termination(dchan);
>  	cancel_work_sync(&chan->irq_work);
> @@ -903,12 +938,18 @@ static void dw_edma_device_synchronize(struct dma_chan *dchan)
>  static void dw_edma_free_chan_resources(struct dma_chan *dchan)
>  {
>  	struct dw_edma_chan *chan = dchan2dw_edma_chan(dchan);
> +	enum dw_edma_ch_irq_mode default_mode =
> +			dw_edma_get_default_irq_mode(chan);
>
>  	dw_edma_device_terminate_all(dchan);
>  	dw_edma_device_synchronize(dchan);
>
> -	scoped_guard(spinlock_irqsave, &chan->vc.lock)
> +	scoped_guard(spinlock_irqsave, &chan->vc.lock) {
>  		chan->configured = false;
> +		/* Avoid a redundant write racing with shared-IRQ readers. */
> +		if (chan->irq_mode != default_mode)
> +			chan->irq_mode = default_mode;
> +	}
>
>  	vchan_free_chan_resources(&chan->vc);
>  }
> diff --git a/include/linux/dma/edma.h b/include/linux/dma/edma.h
> index 3c8e2ef9dee0..54491c9e4b5e 100644
> --- a/include/linux/dma/edma.h
> +++ b/include/linux/dma/edma.h
> @@ -92,6 +92,12 @@ enum dw_edma_chip_flags {
>   * handed over to and driven by the remote side, and the recipe above is
>   * applied by the driving instance.
>   *
> + * On a local eDMA-compatible instance, clients may pass this enum through
> + * dma_slave_config.peripheral_config to switch an idle, unconfigured channel
> + * between LOCAL and REMOTE routing. Before synchronizing a REMOTE channel,
> + * the client must stop remote programming and own every channel affected by
> + * the hardware quiesce.
> + *
>   * HDMA linked-list watermark interrupts have the same LWIE/RWIE guidance. HDMA
>   * non-linked-list mode has dedicated local and remote stop/abort interrupt
>   * enables.
> --
> 2.51.0
>