linux-kernel - Re: [PATCH v2 09/45] arm64: mpam: Advertise the CPUs MPAM limits to the driver

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Message-ID: <20260105170850.000075b5@huawei.com>
Date: Mon, 5 Jan 2026 17:08:50 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Ben Horgan <ben.horgan@....com>
CC: <amitsinght@...vell.com>, <baisheng.gao@...soc.com>,
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Subject: Re: [PATCH v2 09/45] arm64: mpam: Advertise the CPUs MPAM limits to
 the driver

On Fri, 19 Dec 2025 18:11:11 +0000
Ben Horgan <ben.horgan@....com> wrote:

> From: James Morse <james.morse@....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.
> 
> Signed-off-by: James Morse <james.morse@....com>
> Signed-off-by: Ben Horgan <ben.horgan@....com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>