Re: [PATCH v2] PCI: iproc: Use the EROM outbound window on BCMA

[Bjorn Helgaas <helgaas@kernel.org>]

On Fri, Aug 07, 2026 at 06:57:26AM +0300, Semih Baskan wrote:
> The PCIe outbound window base on Northstar depends on the PCIe Gen2 core
> revision. Revision 0x01 uses 0x08000000, 0x40000000 and 0x48000000 for
> controllers 0 to 2, while revision 0x07 (NS-B0) uses 0x08000000,
> 0x20000000 and 0x28000000. Broadcom's own driver branches on the core
> revision for exactly this reason.
> 
> bcm-ns.dtsi is shared by every Northstar SoC, so it cannot carry a value
> that is correct on both. Commit 767012397976 ("ARM: dts: BCM5301X:
> Describe PCIe controllers fully") gave the controllers a ranges property.
> The commit shipped in v7.1.
> 
> With that property present, two things go wrong with this driver:

It looks like you're going to present two problems next.  They should
be bullets so it's obvious what the first is and what the second is,
e.g.,

  - devm_pci_alloc_host_bridge() parses ...

  - When the DT window ...

(or whatever the second item is, I'm not sure where it starts)

> devm_pci_alloc_host_bridge() parses those ranges and requests them, then
> this driver adds its own window and requests the whole list a second
> time, so every controller fails to probe with -EBUSY.
> 
> When the DT window is used, it is only correct on core revision 0x07. On
> revision 0x01 it points at an address the hardware does not decode, and
> the first MMIO access to a BAR takes an imprecise external abort.
> 
> The enumeration ROM reports the correct base for the revision actually
> present, and bcma already provides it as addr_s[0]. Drop any memory
> window that came from the device tree and use that instead, requesting
> only the window this driver owns. This makes the driver correct whether
> or not the DT describes a window.
> 
> When a dropped window does not match what the EROM reports, print a
> warning naming both. The mismatch means the devicetree describes a
> window the hardware does not decode, and that should be fixed in the
> dts rather than ignored silently.
> 
> The same commit also added compatible = "brcm,iproc-pcie", so these
> nodes now match pcie-iproc-platform. With CONFIG_PCIE_IPROC_PLATFORM
> enabled, which is the default on ARCH_BCM_IPROC, that driver binds them
> first and this driver's probe fails inside devm_pci_alloc_host_bridge().
> This patch fixes the configurations where the BCMA driver is the one in
> use; OpenWrt builds that way, with PCIE_IPROC_PLATFORM disabled. The
> platform path takes the DT window as-is and has the same wrong address
> on core revision 0x01, so that side needs a devicetree fix either way.
> 
> Tested on an ASUS RT-N18U (BCM47081) and a Linksys EA9200 (BCM4709),
> both core revision 0x01.
> 
> Fixes: 767012397976 ("ARM: dts: BCM5301X: Describe PCIe controllers fully")
> Tested-by: Rani Hod <rani.hod@gmail.com>
> Cc: stable@vger.kernel.org # v7.1+
> Signed-off-by: Semih Baskan <strst.gs@gmail.com>
> ---
> v1 -> v2: print a warning for every devicetree memory window that does
> not match the EROM window. Requested by Arnd Bergmann:
> https://lore.kernel.org/all/d05ffeca-f289-42dd-b454-5a7c7741c6d5@app.fastmail.com/
> 
> v1: https://lore.kernel.org/all/20260727140939.389-1-strst.gs@gmail.com/
> Applies to v7.2-rc5 and unchanged through v7.2-rc6; the file has no
> commits in between.

FWIW, there's no need to rebase for new -rcs.  We always apply PCI
patches on -rc1 anyway.