Re: [PATCH v2 1/1] MIPS: Malta: Use pcibios_align_resource() to block io range

[Bjorn Helgaas <helgaas@kernel.org>]

On Fri, Oct 17, 2025 at 02:09:03PM +0300, Ilpo Järvinen wrote:
> According to Maciej W. Rozycki <macro@orcam.me.uk>, the
> mips_pcibios_init() for malta adjusts root bus IO resource start
> address to prevent interfering with PIIX4 I/O cycle decoding. Adjusting
> lower bound leaves PIIX4 IO resources outside of the root bus resource
> and assign_fixed_resource_on_bus() does not link the resources into the
> resource tree.
> 
> Prior to commit ae81aad5c2e1 ("MIPS: PCI: Use pci_enable_resources()")
> the arch specific pcibios_enable_resources() did not check if the
> resources were assigned which diverges from what PCI core checks,
> effectively hiding the PIIX4 IO resources were not properly within the
> resource tree. After starting to use pcibios_enable_resources() from
> PCI core, enabling PIIX4 fails:
> 
> ata_piix 0000:00:0a.1: BAR 0 [io  0x01f0-0x01f7]: not claimed; can't enable device
> ata_piix 0000:00:0a.1: probe with driver ata_piix failed with error -22
> 
> MIPS PCI code already has support for enforcing lower bounds using
> PCIBIOS_MIN_IO in pcibios_align_resource() without altering the IO
> window start address itself. Make malta PCI code too to use
> PCIBIOS_MIN_IO.
> 
> Fixes: ae81aad5c2e1 ("MIPS: PCI: Use pci_enable_resources()")
> Fixes: aa0980b80908 ("Fixes for system controllers for Atlas/Malta core cards.")
> Link: https://lore.kernel.org/linux-pci/9085ab12-1559-4462-9b18-f03dcb9a4088@roeck-us.net/
> Link: https://lore.kernel.org/linux-pci/alpine.DEB.2.21.2510132229120.39634@angie.orcam.me.uk/
> Reported-by: Guenter Roeck <linux@roeck-us.net>
> Suggested-by: Maciej W. Rozycki <macro@orcam.me.uk>
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Since ae81aad5c2e1 ("MIPS: PCI: Use pci_enable_resources()") came
through the PCI tree, I'd be happy to merge this as well, given your
ack, Thomas.  It would be ideal to have a tested-by from Guenter.

I provisionally put it on pci/for-linus to facilitate testing.  If it
doesn't solve the problem or you'd rather take it, Thomas, I'll be
glad to drop it.

> ---
> 
> v2:
> 
> - Remove if and always set PCIBIOS_MIN_IO (suggested by Maciej).
> - Minor improvement to the changelog
> 
>  arch/mips/pci/pci-malta.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/mips/pci/pci-malta.c b/arch/mips/pci/pci-malta.c
> index 6aefdf20ca05..2e35aeba45bc 100644
> --- a/arch/mips/pci/pci-malta.c
> +++ b/arch/mips/pci/pci-malta.c
> @@ -230,8 +230,7 @@ void __init mips_pcibios_init(void)
>  	}
>  
>  	/* PIIX4 ACPI starts at 0x1000 */
> -	if (controller->io_resource->start < 0x00001000UL)
> -		controller->io_resource->start = 0x00001000UL;
> +	PCIBIOS_MIN_IO = 0x1000;
>  
>  	iomem_resource.end &= 0xfffffffffULL;			/* 64 GB */
>  	ioport_resource.end = controller->io_resource->end;
> 
> base-commit: 2f2c7254931f41b5736e3ba12aaa9ac1bbeeeb92
> -- 
> 2.39.5
>