Re: [PATCH] ARM: dts: BCM5301X: drop extra AXI bus ranges that break PCIe

On Wed, Jul 29, 2026 at 8:40 AM Arnd Bergmann <[email protected]> wrote:
>
> I saw this in the fixes pull request, and the descriptions
> below don't make much sense to me. I'll hold off on the pull
> request until someone can come up with a fix that they
> can accurately describe.
>
> On Sat, Jul 4, 2026, at 00:17, Rosen Penev wrote:
> > On Sun, Jun 28, 2026 at 4:27 PM <[email protected]> wrote:
> >>
> >> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> >> - [High] Removing the PCI memory ranges from the parent `axi@18000000` bus breaks outbound PCIe memory mapping because the child `pcie` nodes can no longer translate their addresses to CPU physical addresses.
>
> This makes sense to me, but doesn't explain what caused
> the observed bug
>
> >> commit 4f061464281d4964ce46dab60d36a09328f14862
> >> Author: Rosen Penev <[email protected]>
> >>
> >> ARM: dts: BCM5301X: drop extra AXI bus ranges that break PCIe
This patch can be dropped.

https://lore.kernel.org/all/[email protected]/

is the proper solution to the problem.
> >>
> >> This commit removes extra AXI bus ranges that overlap with DRAM on
> >> BCM5301X/BCM470X SoCs. The intention is to restore the original
> >> single-entry mapping and fix PCIe routing issues.
>
> The DRAM ranges on this chip are at 0x00000000 and 0x88000000
> and don't overlap with the axi bus ranges at
> 0x18000000/0x08000000/0x20000000/0x28000000, so the initial
> analysis is wrong.
>
> > With need_ob_cfg = false (no brcm,pcie-ob in bcm-ns.dtsi),
> > iproc_pcie_map_ranges() is never called. The bootloader has already
> > configured the PCIe controller's outbound windows correctly. By
> > removing the extra AXI bus ranges, of_translate_address() fails, those
> > bogus resources are skipped (the OF_BAD_ADDR check at
> > drivers/pci/of.c:377), and the kernel stops registering DRAM addresses
> > as PCI MMIO windows. The hardware continues working with its
> > pre-configured outbound windows.
>
> This sounds like the bootloader configured ranges don't
> match the ones in the devicetree description, which would
> leave three options:
>
> - change the bootloader to match the dts
> - change the dts to match the bootloader
> - change the driver to reconfigure the windows according to DT
>
> Can you check how the OB windows are actually configured
> by the bootloader on your board?
>
>       Arnd