Subject: Re: [PATCH v9 4/5] PCI: dwc: ep: Support BAR subrange inbound mapping via Address Match Mode iATU

From: Niklas Cassel <[email-masked]>
Date: Thu, 22 Jan 2026 10:23:03 +0100

On Thu, Jan 22, 2026 at 05:49:08PM +0900, Koichiro Den wrote:
> Extend dw_pcie_ep_set_bar() to support inbound mappings for BAR
> subranges using Address Match Mode IB iATU when pci_epf_bar.num_submap
> is non-zero.
> 
> Rename the existing BAR-match helper into dw_pcie_ep_ib_atu_bar() and
> introduce dw_pcie_ep_ib_atu_addr() for Address Match Mode. When
> num_submap is non-zero, read the assigned BAR base address and program
> one inbound iATU window per subrange. Validate the submap array before
> programming:
> - each subrange is aligned to pci->region_align
> - subranges cover the whole BAR (no gaps and no overlaps)
> - subranges are sorted in ascending order by offset
> 
> Track Address Match Mode mappings and tear them down on clear_bar() and
> on set_bar() error paths to avoid leaving half-programmed state or
> untranslated BAR holes.
> 
> Advertise this capability by extending the common feature bit
> initializer macro (DWC_EPC_COMMON_FEATURES).
> 
> This enables multiple inbound windows within a single BAR, which is
> useful on platforms where usable BARs are scarce but EPFs need multiple
> inbound regions.
> 
> Reviewed-by: Frank Li <[email-masked]>
> Signed-off-by: Koichiro Den <[email-masked]>
> ---

> @@ -331,6 +503,13 @@ static int dw_pcie_ep_set_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
>  		    ep->epf_bar[bar]->flags != flags)
>  			return -EINVAL;
>  
> +		/*
> +		 * When dynamically changing a BAR, tear down any existing
> +		 * mappings before re-programming.
> +		 */
> +		if (ep->epf_bar[bar]->num_submap || epf_bar->num_submap)
> +			dw_pcie_ep_clear_ib_maps(ep, bar);
> +
>  		/*
>  		 * When dynamically changing a BAR, skip writing the BAR reg, as
>  		 * that would clear the BAR's PCI address assigned by the host.
> @@ -369,8 +548,12 @@ static int dw_pcie_ep_set_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
>  	else
>  		type = PCIE_ATU_TYPE_IO;
>  
> -	ret = dw_pcie_ep_inbound_atu(ep, func_no, type, epf_bar->phys_addr, bar,
> -				     size);
> +	if (epf_bar->num_submap)
> +		ret = dw_pcie_ep_ib_atu_addr(ep, func_no, type, epf_bar);
> +	else
> +		ret = dw_pcie_ep_ib_atu_bar(ep, func_no, type,
> +					    epf_bar->phys_addr, bar, size);

If someone calls set_bar() with a submap, without having called set_bar() first
without a submap, we will still call dw_pcie_ep_ib_atu_addr() here.

To make sure that dw_pcie_ep_ib_atu_addr() cannot be called without already
having a BAR configured, to we perhaps want something like:

diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
index 0567552b784c..fe26b7f7b212 100644
--- a/drivers/pci/controller/dwc/pcie-designware-ep.c
+++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
@@ -487,6 +487,9 @@ static int dw_pcie_ep_set_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
        if ((flags & PCI_BASE_ADDRESS_MEM_TYPE_64) && (bar & 1))
                return -EINVAL;
 
+       if (!ep->epf_bar[bar] && epf_bar->num_submap)
+               return -EINVAL;
+
        /*
         * Certain EPF drivers dynamically change the physical address of a BAR
         * (i.e. they call set_bar() twice, without ever calling clear_bar(), as

or

diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
index 0567552b784c..8aeaa6fe53f9 100644
--- a/drivers/pci/controller/dwc/pcie-designware-ep.c
+++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
@@ -475,6 +475,7 @@ static int dw_pcie_ep_set_bar(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);
        enum pci_barno bar = epf_bar->barno;
+       bool use_addr_match_mode = false;
        size_t size = epf_bar->size;
        enum pci_epc_bar_type bar_type;
        int flags = epf_bar->flags;
@@ -510,6 +511,9 @@ static int dw_pcie_ep_set_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
                if (ep->epf_bar[bar]->num_submap || epf_bar->num_submap)
                        dw_pcie_ep_clear_ib_maps(ep, bar);
 
+               if (epf_bar->num_submap)
+                       use_addr_match_mode = true;
+
                /*
                 * When dynamically changing a BAR, skip writing the BAR reg, as
                 * that would clear the BAR's PCI address assigned by the host.
@@ -548,7 +552,7 @@ static int dw_pcie_ep_set_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
        else
                type = PCIE_ATU_TYPE_IO;
 
-       if (epf_bar->num_submap)
+       if (use_addr_match_mode)
                ret = dw_pcie_ep_ib_atu_addr(ep, func_no, type, epf_bar);
        else
                ret = dw_pcie_ep_ib_atu_bar(ep, func_no, type,