[RFC PATCH v4 05/38] dmaengine: dw-edma: Add a helper to query linked-list region

Koichiro Den
2026-01-18T13:55:05Z

A remote eDMA provider may need to expose the linked-list (LL) memory
region that was configured by platform glue (typically at boot), so the
peer (host) can map it and operate the remote view of the controller.

Export dw_edma_chan_get_ll_region() to return the LL region associated
with a given dma_chan.

Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
drivers/dma/dw-edma/dw-edma-core.c | 26 ++++++++++++++++++++++++++
include/linux/dma/edma.h | 14 ++++++++++++++
2 files changed, 40 insertions(+)

diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
index 0eb8fc1dcc34..c4fb66a9b5f5 100644
--- a/drivers/dma/dw-edma/dw-edma-core.c
+++ b/drivers/dma/dw-edma/dw-edma-core.c
@@ -1209,6 +1209,32 @@ int dw_edma_chan_register_notify(struct dma_chan *dchan,
}
EXPORT_SYMBOL_GPL(dw_edma_chan_register_notify);

+int dw_edma_chan_get_ll_region(struct dma_chan *dchan,
+ struct dw_edma_region *region)
+{
+ struct dw_edma_chip *chip;
+ struct dw_edma_chan *chan;
+
+ if (!dchan || !region || !dchan->device)
+ return -ENODEV;
+
+ chan = dchan2dw_edma_chan(dchan);
+ if (!chan)
+ return -ENODEV;
+
+ chip = chan->dw->chip;
+ if (!(chip->flags & DW_EDMA_CHIP_LOCAL))
+ return -EINVAL;
+
+ if (chan->dir == EDMA_DIR_WRITE)
+ *region = chip->ll_region_wr[chan->id];
+ else
+ *region = chip->ll_region_rd[chan->id];
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(dw_edma_chan_get_ll_region);
+
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("Synopsys DesignWare eDMA controller core driver");
MODULE_AUTHOR("Gustavo Pimentel <gustavo.pimentel@synopsys.com>");
diff --git a/include/linux/dma/edma.h b/include/linux/dma/edma.h
index 3c538246de07..c9ec426e27ec 100644
--- a/include/linux/dma/edma.h
+++ b/include/linux/dma/edma.h
@@ -153,6 +153,14 @@ bool dw_edma_chan_ignore_irq(struct dma_chan *chan);
int dw_edma_chan_register_notify(struct dma_chan *chan,
void (*cb)(struct dma_chan *chan, void *user),
void *user);
+
+/**
+ * dw_edma_chan_get_ll_region - get linked list (LL) memory for a dma_chan
+ * @chan: the target DMA channel
+ * @region: output parameter returning the corresponding LL region
+ */
+int dw_edma_chan_get_ll_region(struct dma_chan *chan,
+ struct dw_edma_region *region);
#else
static inline int dw_edma_probe(struct dw_edma_chip *chip)
{
@@ -182,6 +190,12 @@ static inline int dw_edma_chan_register_notify(struct dma_chan *chan,
{
return -ENODEV;
}
+
+static inline int dw_edma_chan_get_ll_region(struct dma_chan *chan,
+ struct dw_edma_region *region)
+{
+ return -EINVAL;
+}
#endif /* CONFIG_DW_EDMA */

struct pci_epc;
--
2.51.0