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

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Message-ID: <s6bnqkbuugi7oio7ybekdbk3dokpbe2bui2wjltdwajxix2app@wosgmhrfsriv>
Date: Thu, 22 Jan 2026 23:29:02 +0900
From: Koichiro Den <den@...inux.co.jp>
To: Niklas Cassel <cassel@...nel.org>
Cc: jingoohan1@...il.com, mani@...nel.org, lpieralisi@...nel.org, 
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Subject: Re: [PATCH v9 4/5] PCI: dwc: ep: Support BAR subrange inbound
 mapping via Address Match Mode iATU

On Thu, Jan 22, 2026 at 10:23:03AM +0100, Niklas Cassel wrote:
> 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 <Frank.Li@....com>
> > Signed-off-by: Koichiro Den <den@...inux.co.jp>
> > ---
> 
> 
> > @@ -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:

Thanks for the review.
Isn't the existing guard in dw_pcie_ep_ib_atu_addr sufficient?

        [...]
        base = dw_pcie_ep_read_bar_assigned(ep, func_no, bar, epf_bar->flags);
        if (!base) {
                dev_err(dev,
                        "BAR%u not assigned, cannot set up sub-range mappings\n",
                        bar);
                return -EINVAL;
        }

Koichiro

> 
> 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,