Re: [PATCH DNM v3 8/8] arm64: dts: qcom: kaanapali: Add MPAM MSC nodes for the L2 caches

[Rob Herring <robh@kernel.org>]

On Thu, Oct 08, 2026 at 02:41:17PM +0800, Yin Li wrote:
> Add an MPAM MSC device node for each L2 cache. Each MSC is nested
> directly under its L2 cache node so that the cache node is the MSC's
> parent device and its CPU affinity is derived from that cache.
> 
> The L2 cache nodes are placed directly under the root node. The root is
> the root of the physical address space, so each cache node only needs an
> identity 'ranges' property for its nested MSC's 'reg' to be resolved to
> a physical address. The two caches use distinct node names (l2-cache-0
> and l2-cache-1) since a cache node has no MMIO unit-address of its own.
> 
> The nodes are disabled by default. Production firmware does not expose
> MSC register access to the OS, so these nodes can only be enabled on a
> local test setup where firmware permits direct MMIO access to the MSCs.
> This DTS is therefore only an example for other platform DT authors and
> is not intended to be merged.
> 
> Co-developed-by: Huang Yiwei <huang.yiwei@oss.qualcomm.com>
> Signed-off-by: Huang Yiwei <huang.yiwei@oss.qualcomm.com>
> Signed-off-by: Yin Li <yin.li@oss.qualcomm.com>
> ---
>  arch/arm64/boot/dts/qcom/kaanapali.dtsi | 50 +++++++++++++++++++++++++--------
>  1 file changed, 38 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/arm64/boot/dts/qcom/kaanapali.dtsi b/arch/arm64/boot/dts/qcom/kaanapali.dtsi
> index 131fd2a16c54..b1dcb1e9c570 100644
> --- a/arch/arm64/boot/dts/qcom/kaanapali.dtsi
> +++ b/arch/arm64/boot/dts/qcom/kaanapali.dtsi
> @@ -48,12 +48,6 @@ cpu0: cpu@0 {
>  			power-domains = <&cpu_pd0>, <&scmi_perf 0>;
>  			power-domain-names = "psci", "perf";
>  			#cooling-cells = <2>;
> -
> -			l2_0: l2-cache {
> -				compatible = "cache";
> -				cache-level = <2>;
> -				cache-unified;
> -			};
>  		};
>  
>  		cpu1: cpu@100 {
> @@ -120,12 +114,6 @@ cpu6: cpu@10000 {
>  			power-domains = <&cpu_pd6>, <&scmi_perf 1>;
>  			power-domain-names = "psci", "perf";
>  			#cooling-cells = <2>;
> -
> -			l2_1: l2-cache {
> -				compatible = "cache";
> -				cache-level = <2>;
> -				cache-unified;
> -			};
>  		};
>  
>  		cpu7: cpu@10100 {
> @@ -531,6 +519,44 @@ soccp_smp2p_in: slave-kernel {
>  		};
>  	};
>  
> +	l2_0: l2-cache-0 {

cache@19870000

> +		compatible = "cache";

You need a specific compatible here for your implementation.

> +		cache-level = <2>;
> +		cache-unified;
> +		cache-size = <0xc00000>;
> +		ranges;

Are there any other registers for the cache other than the MSC? If not, 
then:

ranges = <0x0 0x19870000 0x10000>;

If there are, you need 'reg' here.

> +
> +		#address-cells = <2>;
> +		#size-cells = <2>;

You don't need 64 bits of address and size here.

> +
> +		msc@19870000 {
> +			compatible = "arm,mpam-msc";
> +			reg = <0x0 0x19870000 0x0 0x10000>;

The MPAM register length is 0x321C.

Rob