Re: [PATCH v2 26/29] arm_mpam: Use long MBWU counters if supported

Jonathan Cameron
2025-09-12T13:29:34Z

On Wed, 10 Sep 2025 20:43:06 +0000
James Morse <james.morse@arm.com> wrote:

> From: Rohit Mathew <rohit.mathew@arm.com>
>
> If the 44 bit (long) or 63 bit (LWD) counters are detected on probing
> the RIS, use long/LWD counter instead of the regular 31 bit mbwu
> counter.
>
> Only 32bit accesses to the MSC are required to be supported by the
> spec, but these registers are 64bits. The lower half may overflow
> into the higher half between two 32bit reads. To avoid this, use
> a helper that reads the top half multiple times to check for overflow.
>
> Signed-off-by: Rohit Mathew <rohit.mathew@arm.com>
> [morse: merged multiple patches from Rohit]
> Signed-off-by: James Morse <james.morse@arm.com>
> Reviewed-by: Ben Horgan <ben.horgan@arm.com>

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>