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Message-ID: <32egn4uhx3dll5es4nzpivg5rdv3hvvrceyznsnnnbbyze7qxu@5z6w45v3jwyf>
Date: Mon, 19 Jan 2026 23:26:06 +0900
From: Koichiro Den <den@...inux.co.jp>
To: Frank Li <Frank.li@....com>
Cc: dave.jiang@...el.com, cassel@...nel.org, mani@...nel.org,
kwilczynski@...nel.org, kishon@...nel.org, bhelgaas@...gle.com, geert+renesas@...der.be,
robh@...nel.org, vkoul@...nel.org, jdmason@...zu.us, allenbh@...il.com,
jingoohan1@...il.com, lpieralisi@...nel.org, linux-pci@...r.kernel.org,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
devicetree@...r.kernel.org, dmaengine@...r.kernel.org, iommu@...ts.linux.dev,
ntb@...ts.linux.dev, netdev@...r.kernel.org, linux-kselftest@...r.kernel.org,
arnd@...db.de, gregkh@...uxfoundation.org, joro@...tes.org, will@...nel.org,
robin.murphy@....com, magnus.damm@...il.com, krzk+dt@...nel.org, conor+dt@...nel.org,
corbet@....net, skhan@...uxfoundation.org, andriy.shevchenko@...ux.intel.com,
jbrunet@...libre.com, utkarsh02t@...il.com
Subject: Re: [RFC PATCH v4 02/38] dmaengine: dw-edma: Add per-channel
interrupt routing control
On Sun, Jan 18, 2026 at 12:03:19PM -0500, Frank Li wrote:
> On Sun, Jan 18, 2026 at 10:54:04PM +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 per-channel interrupt routing mode and export small APIs to
> > configure and query it. 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 APIs are explicitly used,
> > no functional changes.
> >
> > Signed-off-by: Koichiro Den <den@...inux.co.jp>
> > ---
> > drivers/dma/dw-edma/dw-edma-core.c | 52 +++++++++++++++++++++++++++
> > drivers/dma/dw-edma/dw-edma-core.h | 2 ++
> > drivers/dma/dw-edma/dw-edma-v0-core.c | 26 +++++++++-----
> > include/linux/dma/edma.h | 44 +++++++++++++++++++++++
> > 4 files changed, 116 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
> > index b9d59c3c0cb4..059b3996d383 100644
> > --- a/drivers/dma/dw-edma/dw-edma-core.c
> > +++ b/drivers/dma/dw-edma/dw-edma-core.c
> > @@ -768,6 +768,7 @@ 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);
> > @@ -1062,6 +1063,57 @@ int dw_edma_remove(struct dw_edma_chip *chip)
> > }
> > EXPORT_SYMBOL_GPL(dw_edma_remove);
> >
> > +int dw_edma_chan_irq_config(struct dma_chan *dchan,
> > + enum dw_edma_ch_irq_mode mode)
> > +{
> > + struct dw_edma_chan *chan;
> > +
> > + switch (mode) {
> > + case DW_EDMA_CH_IRQ_DEFAULT:
> > + case DW_EDMA_CH_IRQ_LOCAL:
> > + case DW_EDMA_CH_IRQ_REMOTE:
> > + break;
> > + default:
> > + return -EINVAL;
> > + }
> > +
> > + if (!dchan || !dchan->device)
> > + return -ENODEV;
> > +
> > + chan = dchan2dw_edma_chan(dchan);
> > + if (!chan)
> > + return -ENODEV;
> > +
> > + chan->irq_mode = mode;
> > +
> > + dev_vdbg(chan->dw->chip->dev, "Channel: %s[%u] set irq_mode=%u\n",
> > + str_write_read(chan->dir == EDMA_DIR_WRITE),
> > + chan->id, mode);
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(dw_edma_chan_irq_config);
> > +
> > +bool dw_edma_chan_ignore_irq(struct dma_chan *dchan)
> > +{
> > + struct dw_edma_chan *chan;
> > + struct dw_edma *dw;
> > +
> > + if (!dchan || !dchan->device)
> > + return false;
> > +
> > + chan = dchan2dw_edma_chan(dchan);
> > + if (!chan)
> > + return false;
> > +
> > + dw = chan->dw;
> > + if (dw->chip->flags & DW_EDMA_CHIP_LOCAL)
> > + return chan->irq_mode == DW_EDMA_CH_IRQ_REMOTE;
> > + else
> > + return chan->irq_mode == DW_EDMA_CH_IRQ_LOCAL;
> > +}
> > +EXPORT_SYMBOL_GPL(dw_edma_chan_ignore_irq);
> > +
> > MODULE_LICENSE("GPL v2");
> > MODULE_DESCRIPTION("Synopsys DesignWare eDMA controller core driver");
> > MODULE_AUTHOR("Gustavo Pimentel <gustavo.pimentel@...opsys.com>");
> > diff --git a/drivers/dma/dw-edma/dw-edma-core.h b/drivers/dma/dw-edma/dw-edma-core.h
> > index 71894b9e0b15..8458d676551a 100644
> > --- a/drivers/dma/dw-edma/dw-edma-core.h
> > +++ b/drivers/dma/dw-edma/dw-edma-core.h
> > @@ -81,6 +81,8 @@ struct dw_edma_chan {
> >
> > struct msi_msg msi;
> >
> > + enum dw_edma_ch_irq_mode irq_mode;
> > +
> > enum dw_edma_request request;
> > enum dw_edma_status status;
> > u8 configured;
> > diff --git a/drivers/dma/dw-edma/dw-edma-v0-core.c b/drivers/dma/dw-edma/dw-edma-v0-core.c
> > index 2850a9df80f5..80472148c335 100644
> > --- a/drivers/dma/dw-edma/dw-edma-v0-core.c
> > +++ b/drivers/dma/dw-edma/dw-edma-v0-core.c
> > @@ -256,8 +256,10 @@ dw_edma_v0_core_handle_int(struct dw_edma_irq *dw_irq, enum dw_edma_dir dir,
> > for_each_set_bit(pos, &val, total) {
> > chan = &dw->chan[pos + off];
> >
> > - dw_edma_v0_core_clear_done_int(chan);
> > - done(chan);
> > + if (!dw_edma_chan_ignore_irq(&chan->vc.chan)) {
> > + dw_edma_v0_core_clear_done_int(chan);
> > + done(chan);
> > + }
> >
> > ret = IRQ_HANDLED;
> > }
> > @@ -267,8 +269,10 @@ dw_edma_v0_core_handle_int(struct dw_edma_irq *dw_irq, enum dw_edma_dir dir,
> > for_each_set_bit(pos, &val, total) {
> > chan = &dw->chan[pos + off];
> >
> > - dw_edma_v0_core_clear_abort_int(chan);
> > - abort(chan);
> > + if (!dw_edma_chan_ignore_irq(&chan->vc.chan)) {
> > + dw_edma_v0_core_clear_abort_int(chan);
> > + abort(chan);
> > + }
> >
> > ret = IRQ_HANDLED;
> > }
> > @@ -331,7 +335,8 @@ static void dw_edma_v0_core_write_chunk(struct dw_edma_chunk *chunk)
> > j--;
> > if (!j) {
> > control |= DW_EDMA_V0_LIE;
> > - if (!(chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL))
> > + if (!(chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL) &&
> > + chan->irq_mode != DW_EDMA_CH_IRQ_LOCAL)
> > control |= DW_EDMA_V0_RIE;
> > }
> >
> > @@ -408,12 +413,17 @@ static void dw_edma_v0_core_start(struct dw_edma_chunk *chunk, bool first)
> > break;
> > }
> > }
> > - /* Interrupt unmask - done, abort */
> > + /* Interrupt mask/unmask - done, abort */
> > raw_spin_lock_irqsave(&dw->lock, flags);
> >
> > tmp = GET_RW_32(dw, chan->dir, int_mask);
> > - tmp &= ~FIELD_PREP(EDMA_V0_DONE_INT_MASK, BIT(chan->id));
> > - tmp &= ~FIELD_PREP(EDMA_V0_ABORT_INT_MASK, BIT(chan->id));
> > + if (chan->irq_mode == DW_EDMA_CH_IRQ_REMOTE) {
> > + tmp |= FIELD_PREP(EDMA_V0_DONE_INT_MASK, BIT(chan->id));
> > + tmp |= FIELD_PREP(EDMA_V0_ABORT_INT_MASK, BIT(chan->id));
> > + } else {
> > + tmp &= ~FIELD_PREP(EDMA_V0_DONE_INT_MASK, BIT(chan->id));
> > + tmp &= ~FIELD_PREP(EDMA_V0_ABORT_INT_MASK, BIT(chan->id));
> > + }
> > SET_RW_32(dw, chan->dir, int_mask, tmp);
> > /* Linked list error */
> > tmp = GET_RW_32(dw, chan->dir, linked_list_err_en);
> > diff --git a/include/linux/dma/edma.h b/include/linux/dma/edma.h
> > index ffad10ff2cd6..6f50165ac084 100644
> > --- a/include/linux/dma/edma.h
> > +++ b/include/linux/dma/edma.h
> > @@ -60,6 +60,23 @@ enum dw_edma_chip_flags {
> > DW_EDMA_CHIP_LOCAL = BIT(0),
> > };
> >
> > +/*
> > + * 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
> > + * @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_chip - representation of DesignWare eDMA controller hardware
> > * @dev: struct device of the eDMA controller
> > @@ -105,6 +122,22 @@ 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);
> > +/**
> > + * dw_edma_chan_irq_config - configure per-channel interrupt routing
> > + * @chan: DMA channel obtained from dma_request_channel()
> > + * @mode: interrupt routing mode
> > + *
> > + * Returns 0 on success, -EINVAL for invalid @mode, or -ENODEV if @chan does
> > + * not belong to the DesignWare eDMA driver.
> > + */
> > +int dw_edma_chan_irq_config(struct dma_chan *chan,
> > + enum dw_edma_ch_irq_mode mode);
> > +
> > +/**
> > + * dw_edma_chan_ignore_irq - tell whether local IRQ handling should be ignored
> > + * @chan: DMA channel obtained from dma_request_channel()
> > + */
> > +bool dw_edma_chan_ignore_irq(struct dma_chan *chan);
> > #else
> > static inline int dw_edma_probe(struct dw_edma_chip *chip)
> > {
> > @@ -115,6 +148,17 @@ static inline int dw_edma_remove(struct dw_edma_chip *chip)
> > {
> > return 0;
> > }
> > +
> > +static inline int dw_edma_chan_irq_config(struct dma_chan *chan,
> > + enum dw_edma_ch_irq_mode mode)
> > +{
> > + return -ENODEV;
> > +}
> > +
> > +static inline bool dw_edma_chan_ignore_irq(struct dma_chan *chan)
> > +{
> > + return false;
> > +}
>
> I think it'd better go thought
>
> struct dma_slave_config {
> ...
> void *peripheral_config;
> size_t peripheral_size;
>
> };
>
> So DMA consumer can use standard DMAengine API, dmaengine_slave_config().
Using .peripheral_config wasn't something I had initially considered, but I
agree that this is preferable in the sense that it avoids introducing the
additional exported APIs. I'm not entirely sure whether it's clean to use
it for non-peripheral settings in the strict sense, but there seem to be
precedents such as stm32_mdma_dma_config, so I guess it seems acceptable.
If I'm missing something, please correct me.
I'll rework this part as you suggested. Thanks for the guidance.
Koichiro
>
> Frank
> > #endif /* CONFIG_DW_EDMA */
> >
> > struct pci_epc;
> > --
> > 2.51.0
> >
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