Re: [PATCH v7 06/10] PCI: dwc: Implement endpoint DMA channel delegation

[Frank Li]

On Thu, Aug 13, 2026 at 03:37:53PM +0900, Koichiro Den wrote:
> Implement the EPC DMA channel delegation operations for DesignWare
> endpoint controllers. Verify that the DMA engine channel reserved by the
> endpoint function belongs to the integrated DesignWare eDMA instance,
> then hand its interrupt routing to the host.
>
> The DWC eDMA/HDMA engine generates DMA requests with a programmable
> requester function number. For delegated channels, the host-side
> dw-edma-pcie instance bound to the exposed DMA function programs its own
> PCI_FUNC() into the per-channel requester field; the endpoint-side chip
> func_no does
> not participate in that handoff.
>
> Reject VF requests because the RC-programmable DWC eDMA/HDMA register
> window is assigned to a PF BAR only.
>
> Reclaim returns interrupt routing to endpoint ownership. Propagate the
> EPC quiesce request so bind failure paths can reclaim unexposed channels
> without quiescing the DMA engine.
>
> Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>
> ---
> Changes in v7:
>   - Delegate the DMA engine channel already reserved by the endpoint
>     function, matching the API and helper changes in patches 4 and 5.
>
>  .../pci/controller/dwc/pcie-designware-ep.c   | 42 +++++++++++++++++++
>  1 file changed, 42 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> index 0b915824963a..a74d3896e436 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> @@ -858,6 +858,18 @@ dw_pcie_ep_find_bar_rsvd_region(struct dw_pcie_ep *ep,
>  	return NULL;
>  }
>
> +static int dw_pcie_ep_check_edma_vfunc(u8 vfunc_no)
> +{
> +	/*
> +	 * The DWC endpoint databook says it is not possible to assign the
> +	 * DMA/HDMA registers to any Virtual Function.
> +	 */
> +	if (vfunc_no)
> +		return -EOPNOTSUPP;
> +
> +	return 0;
> +}
> +
>  static int
>  dw_pcie_ep_get_aux_resources_count(struct pci_epc *epc, u8 func_no,
>  				   u8 vfunc_no)
> @@ -933,6 +945,34 @@ dw_pcie_ep_get_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
>  	return 0;
>  }
>
> +static int dw_pcie_ep_delegate_dma_chan(struct pci_epc *epc, u8 func_no,
> +					u8 vfunc_no, struct dma_chan *chan)
> +{
> +	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 ret;
> +
> +	ret = dw_pcie_ep_check_edma_vfunc(vfunc_no);
> +	if (ret)
> +		return ret;
> +
> +	if (!edma->dw)
> +		return -ENODEV;
> +
> +	if (!chan || chan->device->dev != edma->dev)
> +		return -EINVAL;
> +
> +	return dw_edma_delegate_chan(chan);
> +}
> +
> +static void dw_pcie_ep_reclaim_dma_chan(struct pci_epc *epc, u8 func_no,
> +					u8 vfunc_no, struct dma_chan *chan,
> +					bool quiesce)
> +{
> +	dw_edma_reclaim_chan(chan, quiesce);
> +}
> +

After use fixed chan_ids, needn't these functins. EPF driver already
find expected dma channel and config it remote only by standard API.

Frank

>  static const struct pci_epc_ops epc_ops = {
>  	.write_header		= dw_pcie_ep_write_header,
>  	.set_bar		= dw_pcie_ep_set_bar,
> @@ -950,6 +990,8 @@ static const struct pci_epc_ops epc_ops = {
>  	.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,
> +	.delegate_dma_chan	= dw_pcie_ep_delegate_dma_chan,
> +	.reclaim_dma_chan	= dw_pcie_ep_reclaim_dma_chan,
>  };
>
>  /**
> --
> 2.51.0
>