Re: [PATCH v5 07/41] arm64: mpam: Advertise the CPUs MPAM limits to the driver

Gavin Shan
2026-03-09T06:43:41Z

On 2/25/26 3:56 AM, Ben Horgan wrote:
> From: James Morse <james.morse@arm.com>
>
> Requestors need to populate the MPAM fields for any traffic they send on
> the interconnect. For the CPUs these values are taken from the
> corresponding MPAMy_ELx register. Each requestor may have a limit on the
> largest PARTID or PMG value that can be used. The MPAM driver has to
> determine the system-wide minimum supported PARTID and PMG values.
>
> To do this, the driver needs to be told what each requestor's limit is.
>
> CPUs are special, but this infrastructure is also needed for the SMMU and
> GIC ITS. Call the helper to tell the MPAM driver what the CPUs can do.
>
> The return value can be ignored by the arch code as it runs well before the
> MPAM driver starts probing.
>
> Tested-by: Gavin Shan <gshan@redhat.com>
> Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
> Tested-by: Peter Newman <peternewman@google.com>
> Tested-by: Zeng Heng <zengheng4@huawei.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> ---
> arch/arm64/kernel/mpam.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>

Reviewed-by: Gavin Shan <gshan@redhat.com>