On Wed, Feb 04, 2026 at 01:06:27PM -0500, Frank Li wrote:

On Wed, Feb 04, 2026 at 11:54:36PM +0900, Koichiro Den wrote:

quoted

Implement pci_epc_ops.get_remote_resources() for the DesignWare PCIe
endpoint controller. Report:
- the integrated eDMA control MMIO window
- the per-channel linked-list regions for read/write engines

This allows endpoint function drivers to discover and map or inform
these resources to a remote peer using the generic EPC API.

Signed-off-by: Koichiro Den <redacted>
---
 .../pci/controller/dwc/pcie-designware-ep.c   | 74 +++++++++++++++++++
 1 file changed, 74 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
index 7e7844ff0f7e..5c0dcbf18d07 100644
--- a/drivers/pci/controller/dwc/pcie-designware-ep.c
+++ b/drivers/pci/controller/dwc/pcie-designware-ep.c

@@ -808,6 +808,79 @@ dw_pcie_ep_get_features(struct pci_epc *epc, u8 func_no, u8 vfunc_no)
 	return ep->ops->get_features(ep);
 }

+static int
+dw_pcie_ep_get_remote_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+				struct pci_epc_remote_resource *resources,
+				int num_resources)
+{
+	struct dw_pcie_ep *ep = epc_get_drvdata(epc);
+	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
+	struct dw_edma_chip *edma = &pci->edma;
+	int ll_cnt = 0, needed, idx = 0;
+	resource_size_t dma_size;
+	phys_addr_t dma_phys;
+	unsigned int i;
+
+	if (!pci->edma_reg_size)
+		return 0;
+
+	dma_phys = pci->edma_reg_phys;
+	dma_size = pci->edma_reg_size;
+
+	for (i = 0; i < edma->ll_wr_cnt; i++)
+		if (edma->ll_region_wr[i].sz)
+			ll_cnt++;
+
+	for (i = 0; i < edma->ll_rd_cnt; i++)
+		if (edma->ll_region_rd[i].sz)
+			ll_cnt++;
+
+	needed = 1 + ll_cnt;
+
+	/* Count query mode */
+	if (!resources || !num_resources)
+		return needed;

^[1] count-query implementation

quoted

+
+	if (num_resources < needed)
+		return -ENOSPC;

How to predict how many 'num_resources' needs?  provide
dw_pcie_ep_get_resource_number()?

Or dw_pcie_ep_get_remote_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
                             struct pci_epc_remote_resource *resources,
                             int *num_resources)

return number_resource validate.  if resources is NULL, just return how
many resource needed.

This is already supported by the current implementation: in
dw_pcie_ep_get_remote_resources(), if resources is NULL (or num_resources
is 0), it returns the number of entries required (see [1] above). Callers
can therefore first query the count and then call again with a properly
sized array.

This behavior is also documented in the core API added in [PATCH v3 06/11]
(pci_epc_get_remote_resources()).

    + * Return:
  > + *   * >= 0: number of resources returned (or required, if @resources is NULL)
    + *   * -EOPNOTSUPP: backend does not support remote resource queries
    + *   * other -errno on failure
    + */
    +int pci_epc_get_remote_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
    +                            struct pci_epc_remote_resource *resources,
    +                            int num_resources)

Thanks,
Koichiro

Frank

quoted

+
+	resources[idx++] = (struct pci_epc_remote_resource) {
+		.type = PCI_EPC_RR_DMA_CTRL_MMIO,
+		.phys_addr = dma_phys,
+		.size = dma_size,
+	};
+
+	/* One LL region per write channel */
+	for (i = 0; i < edma->ll_wr_cnt; i++) {
+		if (!edma->ll_region_wr[i].sz)
+			continue;
+
+		resources[idx++] = (struct pci_epc_remote_resource) {
+			.type = PCI_EPC_RR_DMA_CHAN_DESC,
+			.phys_addr = edma->ll_region_wr[i].paddr,
+			.size = edma->ll_region_wr[i].sz,
+			.u.dma_chan_desc.hw_chan_id = i,
+			.u.dma_chan_desc.ep2rc = true,
+		};
+	}
+
+	/* One LL region per read channel */
+	for (i = 0; i < edma->ll_rd_cnt; i++) {
+		if (!edma->ll_region_rd[i].sz)
+			continue;
+
+		resources[idx++] = (struct pci_epc_remote_resource) {
+			.type = PCI_EPC_RR_DMA_CHAN_DESC,
+			.phys_addr = edma->ll_region_rd[i].paddr,
+			.size = edma->ll_region_rd[i].sz,
+			.u.dma_chan_desc.hw_chan_id = i,
+			.u.dma_chan_desc.ep2rc = false,
+		};
+	}
+
+	return idx;
+}
+
 static const struct pci_epc_ops epc_ops = {
 	.write_header		= dw_pcie_ep_write_header,
 	.set_bar		= dw_pcie_ep_set_bar,

@@ -823,6 +896,7 @@ static const struct pci_epc_ops epc_ops = {
 	.start			= dw_pcie_ep_start,
 	.stop			= dw_pcie_ep_stop,
 	.get_features		= dw_pcie_ep_get_features,
+	.get_remote_resources	= dw_pcie_ep_get_remote_resources,
 };

 /**
--

2.51.0