linux-kernel - Re: [PATCH v3 03/11] dmaengine: dw-edma: Add per-channel interrupt routing control

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Message-ID: <aYS_4Axy9Ts7WDDb@lizhi-Precision-Tower-5810>
Date: Thu, 5 Feb 2026 11:05:52 -0500
From: Frank Li <Frank.li@....com>
To: Koichiro Den <den@...inux.co.jp>
Cc: vkoul@...nel.org, mani@...nel.org, jingoohan1@...il.com,
	lpieralisi@...nel.org, kwilczynski@...nel.org, robh@...nel.org,
	bhelgaas@...gle.com, dmaengine@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 03/11] dmaengine: dw-edma: Add per-channel interrupt
 routing control

On Thu, Feb 05, 2026 at 03:48:30PM +0900, Koichiro Den wrote:
> On Wed, Feb 04, 2026 at 12:42:41PM -0500, Frank Li wrote:
> > On Wed, Feb 04, 2026 at 11:54:31PM +0900, Koichiro Den wrote:
> > > DesignWare EP eDMA can generate interrupts both locally and remotely
> > > (LIE/RIE). Remote eDMA users need to decide, per channel, whether
> > > completions should be handled locally, remotely, or both. Unless
> > > carefully configured, the endpoint and host would race to ack the
> > > interrupt.
> > >
> > > Introduce a dw_edma_peripheral_config that holds per-channel interrupt
> > > routing mode. Update v0 programming so that RIE and local done/abort
> > > interrupt masking follow the selected mode. The default mode keeps the
> > > original behavior, so unless the new peripheral_config is explicitly
> > > used and set, no functional changes.
> > >
> > > For now, HDMA is not supported for the peripheral_config. Until the
> > > support is implemented and validated, explicitly reject it for HDMA to
> > > avoid silently misconfiguring interrupt routing.
> > >
> > > Signed-off-by: Koichiro Den <den@...inux.co.jp>
> > > ---
> > >  drivers/dma/dw-edma/dw-edma-core.c    | 24 +++++++++++++++++++++++
> > >  drivers/dma/dw-edma/dw-edma-core.h    | 13 +++++++++++++
> > >  drivers/dma/dw-edma/dw-edma-v0-core.c | 26 +++++++++++++++++--------
> > >  include/linux/dma/edma.h              | 28 +++++++++++++++++++++++++++
> > >  4 files changed, 83 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
> > > index 38832d9447fd..b4cb02d545bd 100644
> > > --- a/drivers/dma/dw-edma/dw-edma-core.c
> > > +++ b/drivers/dma/dw-edma/dw-edma-core.c
> > > @@ -224,6 +224,29 @@ static int dw_edma_device_config(struct dma_chan *dchan,
> > >  				 struct dma_slave_config *config)
> > >  {
> > >  	struct dw_edma_chan *chan = dchan2dw_edma_chan(dchan);
> > > +	const struct dw_edma_peripheral_config *pcfg;
> > > +
> > > +	/* peripheral_config is optional, default keeps legacy behaviour. */
> > > +	chan->irq_mode = DW_EDMA_CH_IRQ_DEFAULT;
> > > +
> > > +	if (config->peripheral_config) {
> > > +		if (chan->dw->chip->mf == EDMA_MF_HDMA_NATIVE)
> > > +			return -EOPNOTSUPP;
> > > +
> > > +		if (config->peripheral_size < sizeof(*pcfg))
> > > +			return -EINVAL;
> >
> > It is good to check here.
> >
> > > +
> > > +		pcfg = config->peripheral_config;
> >
> > save whole peripheral_config in case need more special peripheral
> > configuration in future.
>
> Ok, while I initially thought a deep copy (snapshot) was unnecessary for
> now, I agree it makes future extensions easier. I'll do so.


>
> >
> > > +		switch (pcfg->irq_mode) {
> > > +		case DW_EDMA_CH_IRQ_DEFAULT:
> > > +		case DW_EDMA_CH_IRQ_LOCAL:
> > > +		case DW_EDMA_CH_IRQ_REMOTE:
> > > +			chan->irq_mode = pcfg->irq_mode;
> > > +			break;
> > > +		default:
> > > +			return -EINVAL;
> > > +		}
> > > +	}
> >
> > use helper function to get irq_mode. [...]
>
> Ok, my current plan is to keep chan->irq_mode as sticky per-channel state,
> and factor out the parsing/validation of irq_mode (from
> config->peripheral_config) into a small helper used by
> dw_edma_device_config() and the new prep_config path.
>
> Does this match what you meant by "helper function"?

yes.

Frank
>
> > [...] I posted combine config and prep by
> > one call.
> >
> > https://lore.kernel.org/dmaengine/20260105-dma_prep_config-v3-0-a8480362fd42@nxp.com/
> >
> > So we use such helper to get irq node after above patch merge. It is not
> > big deal, I can change it later. If provide helper funtions, it will be
> > slice better.
> >
> > >
> > >  	memcpy(&chan->config, config, sizeof(*config));
> > >  	chan->configured = true;
> > > @@ -750,6 +773,7 @@ static int dw_edma_channel_setup(struct dw_edma *dw, u32 wr_alloc, u32 rd_alloc)
> > >  		chan->configured = false;
> > >  		chan->request = EDMA_REQ_NONE;
> > >  		chan->status = EDMA_ST_IDLE;
> > > +		chan->irq_mode = DW_EDMA_CH_IRQ_DEFAULT;
> > >
> > >  		if (chan->dir == EDMA_DIR_WRITE)
> > >  			chan->ll_max = (chip->ll_region_wr[chan->id].sz / EDMA_LL_SZ);
> > ...
> > >
> > > +/*
> > > + * enum dw_edma_ch_irq_mode - per-channel interrupt routing control
> > > + * @DW_EDMA_CH_IRQ_DEFAULT:   LIE=1/RIE=1, local interrupt unmasked
> > > + * @DW_EDMA_CH_IRQ_LOCAL:     LIE=1/RIE=0
> >
> > keep consistent after "," for each enum
>
> Ok, will add ", local interrupt unmasked" for it.
>
> Thanks for the review,
> Koichiro
>
> >
> > Frank
> >
> > > + * @DW_EDMA_CH_IRQ_REMOTE:    LIE=1/RIE=1, local interrupt masked
> > > + *
> > > + * Some implementations require using LIE=1/RIE=1 with the local interrupt
> > > + * masked to generate a remote-only interrupt (rather than LIE=0/RIE=1).
> > > + * See the DesignWare endpoint databook 5.40, "Hint" below "Figure 8-22
> > > + * Write Interrupt Generation".
> > > + */
> > > +enum dw_edma_ch_irq_mode {
> > > +	DW_EDMA_CH_IRQ_DEFAULT	= 0,
> > > +	DW_EDMA_CH_IRQ_LOCAL,
> > > +	DW_EDMA_CH_IRQ_REMOTE,
> > > +};
> > > +
> > > +/**
> > > + * struct dw_edma_peripheral_config - dw-edma specific slave configuration
> > > + * @irq_mode: per-channel interrupt routing control.
> > > + *
> > > + * Pass this structure via dma_slave_config.peripheral_config and
> > > + * dma_slave_config.peripheral_size.
> > > + */
> > > +struct dw_edma_peripheral_config {
> > > +	enum dw_edma_ch_irq_mode irq_mode;
> > > +};
> > > +
> > >  /**
> > >   * struct dw_edma_chip - representation of DesignWare eDMA controller hardware
> > >   * @dev:		 struct device of the eDMA controller
> > > --
> > > 2.51.0
> > >