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

James Morse
2025-10-10T16:53:10Z

Hi Jonathan,

On 12/09/2025 14:29, Jonathan Cameron wrote:
> 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>

Thanks!

Your push back on the 'front facing' thing in the previous patch made some knock on
changes here, but I think they're minor.

Thanks,

James