Re: [PATCH v13 3/7] PCI: dwc: ep: Expose integrated eDMA resources via EPC aux-resource API

[Frank Li]

On Tue, Apr 07, 2026 at 12:57:13AM +0900, Koichiro Den wrote:
> Implement the EPC aux-resource API for DesignWare endpoint controllers
> with integrated eDMA.
>
> Currently, only report an interrupt-emulation doorbell register
> (PCI_EPC_AUX_DOORBELL_MMIO), including its Linux IRQ and the write data
> needed to trigger the interrupt.
>
> If the DMA controller MMIO window is already exposed via a
> platform-owned fixed BAR subregion, also provide the BAR number and
> offset so EPF drivers can reuse it without reprogramming the BAR.
>
> Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>
> ---
Reviewed-by: Frank Li <Frank.Li@xxxxxxx>
> Changes in v13:
>   - Updated to use the revised direct-count aux-resource API.
>
>  .../pci/controller/dwc/pcie-designware-ep.c   | 119 ++++++++++++++++++
>  1 file changed, 119 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> index 386bfb7b2bf6..c3c354265307 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> @@ -9,6 +9,7 @@
>  #include <linux/align.h>
>  #include <linux/bitfield.h>
>  #include <linux/of.h>
> +#include <linux/overflow.h>
>  #include <linux/platform_device.h>
>
>  #include "pcie-designware.h"
> @@ -817,6 +818,122 @@ dw_pcie_ep_get_features(struct pci_epc *epc, u8 func_no, u8 vfunc_no)
>  	return ep->ops->get_features(ep);
>  }
>
> +static const struct pci_epc_bar_rsvd_region *
> +dw_pcie_ep_find_bar_rsvd_region(struct dw_pcie_ep *ep,
> +				enum pci_epc_bar_rsvd_region_type type,
> +				enum pci_barno *bar,
> +				resource_size_t *bar_offset)
> +{
> +	const struct pci_epc_features *features;
> +	const struct pci_epc_bar_desc *bar_desc;
> +	const struct pci_epc_bar_rsvd_region *r;
> +	int i, j;
> +
> +	if (!ep->ops->get_features)
> +		return NULL;
> +
> +	features = ep->ops->get_features(ep);
> +	if (!features)
> +		return NULL;
> +
> +	for (i = BAR_0; i <= BAR_5; i++) {
> +		bar_desc = &features->bar[i];
> +
> +		if (!bar_desc->nr_rsvd_regions || !bar_desc->rsvd_regions)
> +			continue;
> +
> +		for (j = 0; j < bar_desc->nr_rsvd_regions; j++) {
> +			r = &bar_desc->rsvd_regions[j];
> +
> +			if (r->type != type)
> +				continue;
> +
> +			if (bar)
> +				*bar = i;
> +			if (bar_offset)
> +				*bar_offset = r->offset;
> +			return r;
> +		}
> +	}
> +
> +	return NULL;
> +}
> +
> +static int
> +dw_pcie_ep_get_aux_resources_count(struct pci_epc *epc, u8 func_no,
> +				   u8 vfunc_no)
> +{
> +	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;
> +
> +	if (!pci->edma_reg_size)
> +		return 0;
> +
> +	if (edma->db_offset == ~0)
> +		return 0;
> +
> +	return 1;
> +}
> +
> +static int
> +dw_pcie_ep_get_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> +			     struct pci_epc_aux_resource *resources,
> +			     int num_resources)
> +{
> +	struct dw_pcie_ep *ep = epc_get_drvdata(epc);
> +	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> +	const struct pci_epc_bar_rsvd_region *rsvd;
> +	struct dw_edma_chip *edma = &pci->edma;
> +	enum pci_barno dma_ctrl_bar = NO_BAR;
> +	resource_size_t db_offset = edma->db_offset;
> +	resource_size_t dma_ctrl_bar_offset = 0;
> +	resource_size_t dma_reg_size;
> +	int count;
> +
> +	count = dw_pcie_ep_get_aux_resources_count(epc, func_no, vfunc_no);
> +	if (count < 0)
> +		return count;
> +
> +	if (num_resources < count)
> +		return -ENOSPC;
> +
> +	if (!count)
> +		return 0;
> +
> +	dma_reg_size = pci->edma_reg_size;
> +
> +	rsvd = dw_pcie_ep_find_bar_rsvd_region(ep,
> +					       PCI_EPC_BAR_RSVD_DMA_CTRL_MMIO,
> +					       &dma_ctrl_bar,
> +					       &dma_ctrl_bar_offset);
> +	if (rsvd && rsvd->size < dma_reg_size)
> +		dma_reg_size = rsvd->size;
> +
> +	/*
> +	 * For interrupt-emulation doorbells, report a standalone resource
> +	 * instead of bundling it into the DMA controller MMIO resource.
> +	 */
> +	if (range_end_overflows_t(resource_size_t, db_offset,
> +				  sizeof(u32), dma_reg_size))
> +		return -EINVAL;
> +
> +	resources[0] = (struct pci_epc_aux_resource) {
> +		.type = PCI_EPC_AUX_DOORBELL_MMIO,
> +		.phys_addr = pci->edma_reg_phys + db_offset,
> +		.size = sizeof(u32),
> +		.bar = dma_ctrl_bar,
> +		.bar_offset = dma_ctrl_bar != NO_BAR ?
> +				dma_ctrl_bar_offset + db_offset : 0,
> +		.u.db_mmio = {
> +			.irq = edma->db_irq,
> +			.data = 0, /* write 0 to assert */
> +		},
> +	};
> +
> +	return 0;
> +}
> +
>  static const struct pci_epc_ops epc_ops = {
>  	.write_header		= dw_pcie_ep_write_header,
>  	.set_bar		= dw_pcie_ep_set_bar,
> @@ -832,6 +949,8 @@ 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_aux_resources_count	= dw_pcie_ep_get_aux_resources_count,
> +	.get_aux_resources	= dw_pcie_ep_get_aux_resources,
>  };
>
>  /**
> --
> 2.51.0
>