linux-kernel - Re: [RFC PATCH 03/38] arm64: mpam: Advertise the CPUs MPAM limits to the driver

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Message-ID: <20251218103845.000053b3@huawei.com>
Date: Thu, 18 Dec 2025 10:38:45 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: James Morse <james.morse@....com>
CC: <linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>, D
 Scott Phillips OS <scott@...amperecomputing.com>,
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Subject: Re: [RFC PATCH 03/38] arm64: mpam: Advertise the CPUs MPAM limits
 to the driver

On Fri, 5 Dec 2025 21:58:26 +0000
James Morse <james.morse@....com> wrote:

> 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.

Trivial but this commit message line wrap isn't very consistent.

> 
> 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>