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Message-ID: <tpntwbsnraa4dcguhshrqmocnc3n4qik6ezr7hacrcwcq5emd3@ba2bsucpnxmo>
Date: Mon, 9 Feb 2026 13:14:12 +0900
From: Koichiro Den <den@...inux.co.jp>
To: Frank Li <Frank.li@....com>
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-kselftest@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/9] dmaengine: dw-edma: Export per-channel IRQ and
doorbell register offset
On Fri, Feb 06, 2026 at 12:56:24PM -0500, Frank Li wrote:
> On Sat, Feb 07, 2026 at 02:26:40AM +0900, Koichiro Den wrote:
> > Endpoint controller drivers may need to expose or consume eDMA-related
> > resources (e.g. for remote programming or doorbell/self-tests). For
> > that, consumers need a stable way to discover the Linux IRQ used by a
> > given eDMA channel/vector and a register offset suitable for interrupt
> > emulation.
> >
> > Record each channel's IRQ-vector index and store the requested Linux IRQ
> > number. Add a core callback .ch_info() to provide core-specific metadata
> > and implement it for v0.
> >
> > Export dw_edma_chan_info() so that platform drivers can retrieve:
> > - per-channel device name
> > - Linux IRQ number for the channel's interrupt vector
> > - offset of the register used as an emulated-interrupt doorbell within
> > the eDMA register window.
> >
> > Signed-off-by: Koichiro Den <den@...inux.co.jp>
> > ---
> > drivers/dma/dw-edma/dw-edma-core.c | 31 +++++++++++++++++++++++++++
> > drivers/dma/dw-edma/dw-edma-core.h | 14 ++++++++++++
> > drivers/dma/dw-edma/dw-edma-v0-core.c | 7 ++++++
> > include/linux/dma/edma.h | 20 +++++++++++++++++
> > 4 files changed, 72 insertions(+)
> >
> > diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
> > index dd01a9aa8ad8..147a5466e4e7 100644
> > --- a/drivers/dma/dw-edma/dw-edma-core.c
> > +++ b/drivers/dma/dw-edma/dw-edma-core.c
> > @@ -842,6 +842,7 @@ static int dw_edma_channel_setup(struct dw_edma *dw, u32 wr_alloc, u32 rd_alloc)
> > else
> > pos = wr_alloc + chan->id % rd_alloc;
> >
> > + chan->irq_idx = pos;
> > irq = &dw->irq[pos];
> >
> > if (chan->dir == EDMA_DIR_WRITE)
> > @@ -947,6 +948,7 @@ static int dw_edma_irq_request(struct dw_edma *dw,
> > if (irq_get_msi_desc(irq))
> > get_cached_msi_msg(irq, &dw->irq[0].msi);
> >
> > + dw->irq[0].irq = irq;
> > dw->nr_irqs = 1;
> > } else {
> > /* Distribute IRQs equally among all channels */
> > @@ -973,6 +975,7 @@ static int dw_edma_irq_request(struct dw_edma *dw,
> >
> > if (irq_get_msi_desc(irq))
> > get_cached_msi_msg(irq, &dw->irq[i].msi);
> > + dw->irq[i].irq = irq;
> > }
> >
> > dw->nr_irqs = i;
> > @@ -1098,6 +1101,34 @@ int dw_edma_remove(struct dw_edma_chip *chip)
> > }
> > EXPORT_SYMBOL_GPL(dw_edma_remove);
> >
> > +int dw_edma_chan_info(struct dw_edma_chip *chip, unsigned int ch_idx,
> > + struct dw_edma_chan_info *info)
> > +{
> > + struct dw_edma *dw = chip->dw;
> > + struct dw_edma_chan *chan;
> > + struct dma_chan *dchan;
> > + u32 ch_cnt;
> > + int ret;
> > +
> > + if (!chip || !info || !dw)
> > + return -EINVAL;
> > +
> > + ch_cnt = dw->wr_ch_cnt + dw->rd_ch_cnt;
> > + if (ch_idx >= ch_cnt)
> > + return -EINVAL;
> > +
> > + chan = &dw->chan[ch_idx];
> > + dchan = &chan->vc.chan;
> > +
> > + ret = dw_edma_core_ch_info(dw, chan, info);
> > + if (ret)
> > + return ret;
> > +
> > + info->irq = dw->irq[chan->irq_idx].irq;
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(dw_edma_chan_info);
> > +
> > 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 abc97e375484..e92891ed5536 100644
> > --- a/drivers/dma/dw-edma/dw-edma-core.h
> > +++ b/drivers/dma/dw-edma/dw-edma-core.h
> > @@ -82,6 +82,7 @@ struct dw_edma_chan {
> > struct msi_msg msi;
> >
> > enum dw_edma_ch_irq_mode irq_mode;
> > + u32 irq_idx;
>
> can we directly save irq_number?
Yes, that makes sense. I'll address this in v5 together with the changes
based on the discussion here:
https://lore.kernel.org/dmaengine/cuihp4wo5bcku75myq7mfbfvyddwptitiyy6pz5ldq2l6robxk@kghlibxpr7wf/
>
> >
> > enum dw_edma_request request;
> > enum dw_edma_status status;
> > @@ -95,6 +96,7 @@ struct dw_edma_irq {
> > u32 wr_mask;
> > u32 rd_mask;
> > struct dw_edma *dw;
> > + int irq;
> > };
> >
> > struct dw_edma {
> > @@ -129,6 +131,7 @@ struct dw_edma_core_ops {
> > void (*ch_config)(struct dw_edma_chan *chan);
> > void (*debugfs_on)(struct dw_edma *dw);
> > void (*ack_selfirq)(struct dw_edma *dw);
> > + void (*ch_info)(struct dw_edma_chan *chan, struct dw_edma_chan_info *info);
> > };
> >
> > struct dw_edma_sg {
> > @@ -219,6 +222,17 @@ int dw_edma_core_ack_selfirq(struct dw_edma *dw)
> > return 0;
> > }
> >
> > +static inline
> > +int dw_edma_core_ch_info(struct dw_edma *dw, struct dw_edma_chan *chan,
> > + struct dw_edma_chan_info *info)
>
> wrap int to previous line, check others.
Thanks for pointing that out. I'll update it for the same reasons as
discussed here:
https://lore.kernel.org/dmaengine/qktad6ggosznbznej7n2luxwkhr34f3egtojzjnkry4v2balbh@sfxxoii5yxoa/
Thanks,
Koichiro
>
> Frank
> > +{
> > + if (!dw->core->ch_info)
> > + return -EOPNOTSUPP;
> > +
> > + dw->core->ch_info(chan, info);
> > + return 0;
> > +}
> > +
> > static inline
> > bool dw_edma_core_ch_ignore_irq(struct dw_edma_chan *chan)
> > {
> > diff --git a/drivers/dma/dw-edma/dw-edma-v0-core.c b/drivers/dma/dw-edma/dw-edma-v0-core.c
> > index 68e0d088570d..9c7908a76fff 100644
> > --- a/drivers/dma/dw-edma/dw-edma-v0-core.c
> > +++ b/drivers/dma/dw-edma/dw-edma-v0-core.c
> > @@ -529,6 +529,12 @@ static void dw_edma_v0_core_ack_selfirq(struct dw_edma *dw)
> > SET_BOTH_32(dw, int_clear, 0);
> > }
> >
> > +static void dw_edma_v0_core_ch_info(struct dw_edma_chan *chan,
> > + struct dw_edma_chan_info *info)
> > +{
> > + info->db_offset = offsetof(struct dw_edma_v0_regs, rd_int_status);
> > +}
> > +
> > static const struct dw_edma_core_ops dw_edma_v0_core = {
> > .off = dw_edma_v0_core_off,
> > .ch_count = dw_edma_v0_core_ch_count,
> > @@ -538,6 +544,7 @@ static const struct dw_edma_core_ops dw_edma_v0_core = {
> > .ch_config = dw_edma_v0_core_ch_config,
> > .debugfs_on = dw_edma_v0_core_debugfs_on,
> > .ack_selfirq = dw_edma_v0_core_ack_selfirq,
> > + .ch_info = dw_edma_v0_core_ch_info,
> > };
> >
> > void dw_edma_v0_core_register(struct dw_edma *dw)
> > diff --git a/include/linux/dma/edma.h b/include/linux/dma/edma.h
> > index 53b31a974331..9fd78dc313e5 100644
> > --- a/include/linux/dma/edma.h
> > +++ b/include/linux/dma/edma.h
> > @@ -129,10 +129,23 @@ struct dw_edma_chip {
> > struct dw_edma *dw;
> > };
> >
> > +/**
> > + * struct dw_edma_chan_info - DW eDMA channel metadata
> > + * @irq: Linux IRQ number used by this channel's interrupt vector
> > + * @db_offset: offset within the eDMA register window that can be used as
> > + * an interrupt-emulation doorbell for this channel
> > + */
> > +struct dw_edma_chan_info {
> > + int irq;
> > + resource_size_t db_offset;
> > +};
> > +
> > /* Export to the platform drivers */
> > #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_chan_info(struct dw_edma_chip *chip, unsigned int ch_idx,
> > + struct dw_edma_chan_info *info);
> > #else
> > static inline int dw_edma_probe(struct dw_edma_chip *chip)
> > {
> > @@ -143,6 +156,13 @@ static inline int dw_edma_remove(struct dw_edma_chip *chip)
> > {
> > return 0;
> > }
> > +
> > +static inline int dw_edma_chan_info(struct dw_edma_chip *chip,
> > + unsigned int ch_idx,
> > + struct dw_edma_chan_info *info)
> > +{
> > + return -ENODEV;
> > +}
> > #endif /* CONFIG_DW_EDMA */
> >
> > #endif /* _DW_EDMA_H */
> > --
> > 2.51.0
> >
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