Re: [PATCH v7 5/9] PCI: dwc: ep: Expose integrated eDMA resources via EPC aux-resource API

On Mon, Feb 16, 2026 at 03:12:53PM +0100, Niklas Cassel wrote:
> On Mon, Feb 16, 2026 at 01:38:43AM +0900, Koichiro Den wrote:
> > Implement the EPC aux-resource API for DesignWare endpoint controllers
> > with integrated eDMA.
> > 
> > Report:
> >   - DMA controller MMIO window (PCI_EPC_AUX_DMA_CTRL_MMIO)
> >   - interrupt-emulation doorbell register (PCI_EPC_AUX_DOORBELL_MMIO),
> >     including its Linux IRQ
> >   - per-channel LL descriptor regions (PCI_EPC_AUX_DMA_CHAN_DESC)
> > 
> > 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 <[email protected]>
> > ---
> >  .../pci/controller/dwc/pcie-designware-ep.c   | 149 ++++++++++++++++++
> >  1 file changed, 149 insertions(+)
> > 
> > diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> > index 7e7844ff0f7e..ffd2797b7b81 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> > +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> > @@ -808,6 +808,154 @@ 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(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;
> > +	int ll_cnt = 0, needed, idx = 0;
> > +	resource_size_t db_offset = edma->db_offset;
> > +	resource_size_t dma_ctrl_bar_offset = 0;
> > +	resource_size_t dma_reg_size;
> > +	unsigned int i;
> > +
> > +	if (!pci->edma_reg_size)
> > +		return 0;
> > +
> > +	dma_reg_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 + (db_offset != ~0 ? 1 : 0);
> > +
> > +	/* Count query mode */
> > +	if (!resources || !num_resources)
> > +		return needed;
> > +
> > +	if (num_resources < needed)
> > +		return -ENOSPC;
> > +
> > +	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;
> > +
> > +	/* DMA register block */
> > +	resources[idx++] = (struct pci_epc_aux_resource) {
> > +		.type = PCI_EPC_AUX_DMA_CTRL_MMIO,
> > +		.phys_addr = pci->edma_reg_phys,
> > +		.size = dma_reg_size,
> > +		.bar = dma_ctrl_bar,
> > +		.bar_offset = dma_ctrl_bar_offset,
> > +	};
> > +
> > +	/*
> > +	 * For interrupt-emulation doorbells, report a standalone resource
> > +	 * instead of bundling it into the DMA controller MMIO resource.
> > +	 */
> > +	if (db_offset != ~0) {
> > +		if (dma_reg_size < sizeof(u32) ||
> > +		    db_offset > dma_reg_size - sizeof(u32))
> 
> In your other patch, you used:
> 
> 	if (size_add(offset, sizeof(u32)) > epf->bar[bar].size)
> 
> For consistency, do you perhaps want to use the same here?
> 
> size_add(db_offset, sizeof(u32)) > dma_reg_size ?

db_offset and dma_reg_size are resource_size_t, not size_t. resource_size_t can
be wider than size_t on some 32-bit builds with CONFIG_PHYS_ADDR_T_64BIT, so
using size_add() would potentially introduce a narrowing conversion. For that
reason, I avoided it.

If that would be preferable, I'm happy to switch this part to something like:

        if (db_offset != ~0) {
                if (range_end_overflows_t(resource_size_t, db_offset,
                                          sizeof(u32), dma_reg_size))
                        return -EINVAL;

or alternatively use check_add_overflow().

Best regards,
Koichiro

> 
> 
> 
> 
> Kind regards,
> Niklas