On Mon, Feb 09, 2026 at 11:13:40AM -0500, Frank Li wrote: > On Mon, Feb 09, 2026 at 09:53:10PM +0900, Koichiro Den wrote: > > Some DesignWare PCIe endpoint controllers integrate a DesignWare > > eDMA/HDMA instance. In remote eDMA use cases (e.g. exposing the eDMA > > MMIO window and per-channel linked-list regions to a peer via BARs), > > consumers need a stable way to discover: > > - the Linux IRQ number associated with a given channel's interrupt > > vector, > > - an offset within the eDMA register window that can be used as an > > interrupt-emulation doorbell for that channel. > > > > Store the requested Linux IRQ number in struct dw_edma_irq at IRQ > > request time and cache per-channel metadata in struct dw_edma_chip > > (ch_info_wr/rd) during channel setup. Add a core callback, .ch_info(), > > to fill core-specific metadata such as the doorbell register offset; > > implement it for the v0 eDMA core (use rd_int_status as a suitable > > doorbell target) and provide a placeholder for HDMA until the correct > > offset is known. > > > > No functional change for normal DMA operation. This only makes the > > metadata available to controller/platform drivers that need to expose or > > consume eDMA-related resources. > > > > Signed-off-by: Koichiro Den <[email protected]> > > --- > > drivers/dma/dw-edma/dw-edma-core.c | 9 +++++++++ > > drivers/dma/dw-edma/dw-edma-core.h | 9 +++++++++ > > drivers/dma/dw-edma/dw-edma-v0-core.c | 11 +++++++++++ > > drivers/dma/dw-edma/dw-hdma-v0-core.c | 8 ++++++++ > > include/linux/dma/edma.h | 17 +++++++++++++++++ > > 5 files changed, 54 insertions(+) > > > > diff --git a/drivers/dma/dw-edma/dw-edma-core.c > > b/drivers/dma/dw-edma/dw-edma-core.c > > index fe131abf1ca3..bd5ff4a4431a 100644 > > --- a/drivers/dma/dw-edma/dw-edma-core.c > > +++ b/drivers/dma/dw-edma/dw-edma-core.c > > @@ -760,6 +760,7 @@ static int dw_edma_channel_setup(struct dw_edma *dw, > > u32 wr_alloc, u32 rd_alloc) > > { > > struct dw_edma_chip *chip = dw->chip; > > struct device *dev = chip->dev; > > + struct dw_edma_ch_info *info; > > struct dw_edma_chan *chan; > > struct dw_edma_irq *irq; > > struct dma_device *dma; > > @@ -779,9 +780,11 @@ static int dw_edma_channel_setup(struct dw_edma *dw, > > u32 wr_alloc, u32 rd_alloc) > > if (i < dw->wr_ch_cnt) { > > chan->id = i; > > chan->dir = EDMA_DIR_WRITE; > > + info = &chip->ch_info_wr[chan->id]; > > } else { > > chan->id = i - dw->wr_ch_cnt; > > chan->dir = EDMA_DIR_READ; > > + info = &chip->ch_info_rd[chan->id]; > > } > > > > chan->configured = false; > > @@ -807,6 +810,10 @@ static int dw_edma_channel_setup(struct dw_edma *dw, > > u32 wr_alloc, u32 rd_alloc) > > > > irq = &dw->irq[pos]; > > > > + /* cache channel-specific info */ > > + dw_edma_core_ch_info(dw, chan, info); > > + info->irq = irq->irq; > > + > > if (chan->dir == EDMA_DIR_WRITE) > > irq->wr_mask |= BIT(chan->id); > > else > > @@ -910,6 +917,7 @@ 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 */ > > @@ -936,6 +944,7 @@ 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; > > diff --git a/drivers/dma/dw-edma/dw-edma-core.h > > b/drivers/dma/dw-edma/dw-edma-core.h > > index 50b87b63b581..82f8f3b38752 100644 > > --- a/drivers/dma/dw-edma/dw-edma-core.h > > +++ b/drivers/dma/dw-edma/dw-edma-core.h > > @@ -93,6 +93,7 @@ struct dw_edma_irq { > > u32 wr_mask; > > u32 rd_mask; > > struct dw_edma *dw; > > + int irq; > > }; > > > > struct dw_edma { > > @@ -127,6 +128,7 @@ struct dw_edma_core_ops { > > void (*ch_config)(struct dw_edma_chan *chan); > > void (*debugfs_on)(struct dw_edma *dw); > > void (*ack_emulated_irq)(struct dw_edma *dw); > > + void (*ch_info)(struct dw_edma_chan *chan, struct dw_edma_ch_info > > *info); > > }; > > > > struct dw_edma_sg { > > @@ -216,4 +218,11 @@ static inline int dw_edma_core_ack_emulated_irq(struct > > dw_edma *dw) > > return 0; > > } > > > > +static inline void > > +dw_edma_core_ch_info(struct dw_edma *dw, struct dw_edma_chan *chan, > > + struct dw_edma_ch_info *info) > > +{ > > + dw->core->ch_info(chan, info); > > +} > > + > > #endif /* _DW_EDMA_CORE_H */ > > diff --git a/drivers/dma/dw-edma/dw-edma-v0-core.c > > b/drivers/dma/dw-edma/dw-edma-v0-core.c > > index 82b9c063c10f..0b8d4b6a5e26 100644 > > --- a/drivers/dma/dw-edma/dw-edma-v0-core.c > > +++ b/drivers/dma/dw-edma/dw-edma-v0-core.c > > @@ -519,6 +519,16 @@ static void dw_edma_v0_core_ack_emulated_irq(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_ch_info *info) > > +{ > > + /* > > + * rd_int_status is chosen arbitrarily, but wr_int_status would be > > + * equally suitable. > > + */ > > + 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, > > @@ -528,6 +538,7 @@ 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_emulated_irq = dw_edma_v0_core_ack_emulated_irq, > > + .ch_info = dw_edma_v0_core_ch_info, > > }; > > > > void dw_edma_v0_core_register(struct dw_edma *dw) > > diff --git a/drivers/dma/dw-edma/dw-hdma-v0-core.c > > b/drivers/dma/dw-edma/dw-hdma-v0-core.c > > index e3f8db4fe909..1076b394c45f 100644 > > --- a/drivers/dma/dw-edma/dw-hdma-v0-core.c > > +++ b/drivers/dma/dw-edma/dw-hdma-v0-core.c > > @@ -283,6 +283,13 @@ static void dw_hdma_v0_core_debugfs_on(struct dw_edma > > *dw) > > dw_hdma_v0_debugfs_on(dw); > > } > > > > +static void dw_hdma_v0_core_ch_info(struct dw_edma_chan *chan, > > + struct dw_edma_ch_info *info) > > +{ > > + /* Implement once the correct offset is known. */ > > + info->db_offset = ~0; > > +} > > + > > static const struct dw_edma_core_ops dw_hdma_v0_core = { > > .off = dw_hdma_v0_core_off, > > .ch_count = dw_hdma_v0_core_ch_count, > > @@ -291,6 +298,7 @@ static const struct dw_edma_core_ops dw_hdma_v0_core = { > > .start = dw_hdma_v0_core_start, > > .ch_config = dw_hdma_v0_core_ch_config, > > .debugfs_on = dw_hdma_v0_core_debugfs_on, > > + .ch_info = dw_hdma_v0_core_ch_info, > > }; > > > > void dw_hdma_v0_core_register(struct dw_edma *dw) > > diff --git a/include/linux/dma/edma.h b/include/linux/dma/edma.h > > index 3080747689f6..921250204a08 100644 > > --- a/include/linux/dma/edma.h > > +++ b/include/linux/dma/edma.h > > @@ -60,6 +60,19 @@ enum dw_edma_chip_flags { > > DW_EDMA_CHIP_LOCAL = BIT(0), > > }; > > > > +/** > > + * struct dw_edma_ch_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_ch_info { > > + int irq; > > + > > + /* Fields below are filled in by dw_edma_core_ops->ch_info() */ > > + resource_size_t db_offset; > > +}; > > + > > /** > > * struct dw_edma_chip - representation of DesignWare eDMA controller > > hardware > > * @dev: struct device of the eDMA controller > > @@ -96,6 +109,10 @@ struct dw_edma_chip { > > struct dw_edma_region dt_region_wr[EDMA_MAX_WR_CH]; > > struct dw_edma_region dt_region_rd[EDMA_MAX_RD_CH]; > > > > + /* cached channel info */ > > + struct dw_edma_ch_info ch_info_wr[EDMA_MAX_WR_CH]; > > + struct dw_edma_ch_info ch_info_rd[EDMA_MAX_RD_CH]; > > + > > suppose this info only used in side dw edma driver, so it should be in > dw_edma. > > dw_edma_chip is useful to exchange informaiton between EPC/PCI controller > and dma engine when call dw_edma_probe().
These cached values are consumed on the EPC side, while struct dw_edma is opaque there. Putting them into struct dw_edma would require an exported accessor (again), which I was hoping to avoid. Does that sound reasonable to you? Thanks for the review, Koichiro > > Frand > > > enum dw_edma_map_format mf; > > > > struct dw_edma *dw; > > -- > > 2.51.0 > >
