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

Niklas Cassel
2026-02-10T10:25:22Z

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@valinux.co.jp>
> ---
> 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@kernel.org>

Considering that this patch has not been picked up yet,
perhaps resend it using [PATCH RESEND].

Kind regards,
Niklas