SiFive FU740 PCI driver fails on 6.18-rc1

[Conor Dooley]

On Mon, Oct 13, 2025 at 01:49:39PM +0530, Krishna Chaitanya Chundru wrote:
> 
> 
> On 10/13/2025 12:44 PM, Ron Economos wrote:
> > The SiFive FU740 PCI driver fails on the HiFive Unmatched board with
> > Linux 6.18-rc1. The error message is:
> > 
> > [    3.166624] fu740-pcie e00000000.pcie: host bridge
> > /soc/pcie at e00000000 ranges:
> > [    3.166706] fu740-pcie e00000000.pcie:       IO
> > 0x0060080000..0x006008ffff -> 0x0060080000
> > [    3.166767] fu740-pcie e00000000.pcie:      MEM
> > 0x0060090000..0x007fffffff -> 0x0060090000
> > [    3.166805] fu740-pcie e00000000.pcie:      MEM
> > 0x2000000000..0x3fffffffff -> 0x2000000000
> > [    3.166950] fu740-pcie e00000000.pcie: ECAM at [mem
> > 0xdf0000000-0xdffffffff] for [bus 00-ff]
> > [    3.579500] fu740-pcie e00000000.pcie: No iATU regions found
> > [    3.579552] fu740-pcie e00000000.pcie: Failed to configure iATU in
> > ECAM mode
> > [    3.579655] fu740-pcie e00000000.pcie: probe with driver fu740-pcie
> > failed with error -22
> > 
> > The normal message (on Linux 6.17.2) is:
> > 
> > [    3.381487] fu740-pcie e00000000.pcie: host bridge
> > /soc/pcie at e00000000 ranges:
> > [    3.381584] fu740-pcie e00000000.pcie:       IO
> > 0x0060080000..0x006008ffff -> 0x0060080000
> > [    3.381682] fu740-pcie e00000000.pcie:      MEM
> > 0x0060090000..0x007fffffff -> 0x0060090000
> > [    3.381724] fu740-pcie e00000000.pcie:      MEM
> > 0x2000000000..0x3fffffffff -> 0x2000000000
> > [    3.484809] fu740-pcie e00000000.pcie: iATU: unroll T, 8 ob, 8 ib,
> > align 4K, limit 4096G
> > [    3.683678] fu740-pcie e00000000.pcie: PCIe Gen.1 x8 link up
> > [    3.883674] fu740-pcie e00000000.pcie: PCIe Gen.3 x8 link up
> > [    3.987678] fu740-pcie e00000000.pcie: PCIe Gen.3 x8 link up
> > [    3.988164] fu740-pcie e00000000.pcie: PCI host bridge to bus 0000:00
> > 
> > Reverting the following commits solves the issue.
> > 
> > 0da48c5b2fa731b21bc523c82d927399a1e508b0 PCI: dwc: Support ECAM
> > mechanism by enabling iATU 'CFG Shift Feature'
> > 
> > 4660e50cf81800f82eeecf743ad1e3e97ab72190 PCI: qcom: Prepare for the DWC
> > ECAM enablement
> > 
> > f6fd357f7afbeb34a633e5688a23b9d7eb49d558 PCI: dwc: Prepare the driver
> > for enabling ECAM mechanism using iATU 'CFG Shift Feature'
> > 
> Hi Ron,
> 
> can you try with this change.
> Looks like fu740-pcie driver has 256MB space of config space so dwc
> driver is trying to enable ecam and seeing failures while enabling.
> 
> you can try two options 1 is to enable ecam if your hardware supports
> it and other is to use native method like below.

> If you want to enable
> ecam your config space should start with dbi address and should have
> 256Mb aligned 256Mb memory of config space. Uf you want to enable ecam
> and had this memory requirement fulfilled, try to change your devicetree
> by starting config space with dbi start address and give it a try.

If it worked before your changes, but now does not, I am not going to
accept a dts change to make it work again FYI.

> 
> diff --git a/drivers/pci/controller/dwc/pcie-fu740.c
> b/drivers/pci/controller/dwc/pcie-fu740.c
> index 66367252032b..b5e0f016a580 100644
> --- a/drivers/pci/controller/dwc/pcie-fu740.c
> +++ b/drivers/pci/controller/dwc/pcie-fu740.c
> @@ -328,6 +328,8 @@ static int fu740_pcie_probe(struct platform_device
> *pdev)
> 
>         platform_set_drvdata(pdev, afp);
> 
> +       pci->pp.native_ecam = true;
> +
>         return dw_pcie_host_init(&pci->pp);
>  }
> 
> - Krishna Chaitanya.
> > 
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