Re: [PATCH v2] ACPI: scan: Do not combine resources that overlap completely

[Jarkko Sakkinen <jarkko@kernel.org>]

On Thu, Aug 20, 2026 at 09:11:14PM +0200, Rafael J. Wysocki wrote:
> From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> 
> Commit f234fdaae1ca ("ACPI: scan: Avoid registering platform devices
> with resource overlaps") attempted to avoid platform device registration
> errors due to overlaps of resources of the same type returned by the
> same _CRS object in the ACPI tables.  It did that by combining two or
> more overlapping resources into one, but it went too far and also
> caused resources that overlap completely to be combined which broke
> the arm-cmn driver that expects two MMIO resources to be present for
> each device it binds to and it expects those two resources to overlap
> completely.
> 
> Address this issue by adding checks for completely overlapping
> resources to acpi_platform_adjust_resources() and add a comment
> explaining what is done there.
> 
> Fixes: f234fdaae1ca ("ACPI: scan: Avoid registering platform devices with resource overlaps")
> Reported-by: Nathan Chancellor <nathan@kernel.org> 
> Tested-by: Nathan Chancellor <nathan@kernel.org> 
> Closes: https://lore.kernel.org/linux-acpi/20260819003752.GA3063251@ax162/
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
> 
> v1 -> v2:
>    * It is better to check for complete overlaps both ways as suggested
>      by Sashiko.
> 
> @Julien: I would appreciate testing this on the machine that needed
> commit f234fdaae1ca.
> 
> ---
>  drivers/acpi/acpi_platform.c |    8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> --- a/drivers/acpi/acpi_platform.c
> +++ b/drivers/acpi/acpi_platform.c
> @@ -85,7 +85,13 @@ static unsigned int acpi_platform_adjust
>  	for (i = 0; i < count; ) {
>  		struct resource *res = &resources[i];
>  
> -		if (resource_type(new_res) != resource_type(res) ||
> +		/*
> +		 * Look for overlaps of resources of the same type that would
> +		 * cause resource insertion to fail down the road.
> +		 */
> +		if (__resource_contains_unbound(res, new_res) ||
> +		    __resource_contains_unbound(new_res, res) ||
> +		    resource_type(new_res) != resource_type(res) ||
>  		    !resource_union(new_res, res, new_res)) {
>  			i++;
>  			continue;
> 
> 
> 


Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

BR, Jarkko