Re: [PATCH] PCI: dwc: rcar-gen4-ep: Program Resizable BARs and drop 1MiB BAR limit

[Koichiro Den]

On Tue, Feb 10, 2026 at 11:25:16AM +0100, Niklas Cassel wrote:
> On Thu, Oct 23, 2025 at 04:22:17PM +0900, Koichiro Den wrote:
> > R-Car Gen4 (S4) exposes BAR0 and BAR2 as Resizable BARs. Program them
> > accordingly by using dw_pcie_ep_set_bar_resizable() instead of the
> > programmable BAR path.
> > 
> > Before this change the driver left the Resizable BAR capability
> > untouched and only wrote the BAR register, so the RC enumerated BAR0/2
> > as 1 MiB regardless of the size requested by the endpoint function. For
> > example, configuring a 2 MiB window for pci-epf-vntb still produced:
> > 
> >   ntb_hw_epf 0000:01:00.0: \
> >   Size:0x0000000000200000 is greater than the MW size 0x0000000000100000
> > 
> > Program the Resizable BAR control so the RC sees the requested size and
> > ntb_transport can use larger memory windows.
> > 
> > Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>
> > ---
> >  drivers/pci/controller/dwc/pcie-rcar-gen4.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/pci/controller/dwc/pcie-rcar-gen4.c b/drivers/pci/controller/dwc/pcie-rcar-gen4.c
> > index 80778917d2dd..dbad741b8286 100644
> > --- a/drivers/pci/controller/dwc/pcie-rcar-gen4.c
> > +++ b/drivers/pci/controller/dwc/pcie-rcar-gen4.c
> > @@ -421,7 +421,9 @@ static int rcar_gen4_pcie_ep_raise_irq(struct dw_pcie_ep *ep, u8 func_no,
> >  
> >  static const struct pci_epc_features rcar_gen4_pcie_epc_features = {
> >  	.msi_capable = true,
> > +	.bar[BAR_0] = { .type = BAR_RESIZABLE, },
> >  	.bar[BAR_1] = { .type = BAR_RESERVED, },
> > +	.bar[BAR_2] = { .type = BAR_RESIZABLE, },
> >  	.bar[BAR_3] = { .type = BAR_RESERVED, },
> >  	.bar[BAR_4] = { .type = BAR_FIXED, .fixed_size = 256 },
> >  	.bar[BAR_5] = { .type = BAR_RESERVED, },
> > -- 
> > 2.48.1
> > 
> 
> Reviewed-by: Niklas Cassel <cassel@xxxxxxxxxx>
> 
> Considering that this patch has not been picked up yet,
> perhaps resend it using [PATCH RESEND].

Thanks for the Reviewed-by. As almost four months have passed, in hindsight the
commit message sounds a bit too awkward now..
I'd like to update it to at least remove ntb-specific wording and make it more
compact and concise, like this:

  PCI: dwc: rcar-gen4-ep: Mark BAR0 and BAR2 as Resizable BARs

  R-Car Gen4 (S4) implements the PCIe Resizable BAR capability for BAR0 and
  BAR2. Advertise them as BAR_RESIZABLE so EPF-requested BAR sizes are
  reflected to the host.

If this looks good to you, would it be okay for me to keep the Reviewed-by
tag? There will be no code changes, only this commit message rewording in
the RESEND.

Best regards,
Koichiro

> 
> 
> Kind regards,
> Niklas