Re: [PATCH v1 03/11] arm_mpam: Set mpam_feat_msmon_mbwu_31counter when there are bandwidth counters

[Gavin Shan]

On 7/10/26 9:55 PM, Ben Horgan wrote:
> If there are memory bandwidth counters then there are 31 bit counters even
> if there are also 44 bit counters or 63 bit counters.
>
> Set the 31 bit bandwidth counter feature bit whenever there are bandwidth
> counters.
>
> Fixes: fdc29a141d63 ("arm_mpam: Probe for long/lwd mbwu counters")
> Signed-off-by: Ben Horgan <ben.horgan@xxxxxxx>
> ---
>   drivers/resctrl/mpam_devices.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)

It might be worthwhile to put some context in the commit log helping readers
to correlate to the specification. What I found is something like below in
section 8.2.1.2 Long MBWU counter and capture of ARM IHI 0099A.a:

In MSMON_MBWU, the VALUE field is always 31 bits. If MSMON_MBWU_L is implemented,
the length of the VALUE field is either 63 or 44 bits as set by MPAMF_MBWUMON_IDR.LWD.

> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
> index acfa9a4dc2fc..11b10c3bc334 100644
> --- a/drivers/resctrl/mpam_devices.c
> +++ b/drivers/resctrl/mpam_devices.c
> @@ -930,9 +930,9 @@ static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
>   						mpam_set_feature(mpam_feat_msmon_mbwu_63counter, props);
>   					else
>   						mpam_set_feature(mpam_feat_msmon_mbwu_44counter, props);
> -				} else {
> -					mpam_set_feature(mpam_feat_msmon_mbwu_31counter, props);
>   				}
> +
> +				mpam_set_feature(mpam_feat_msmon_mbwu_31counter, props);
>   			}
>   		}
>   	}

Thanks,
Gavin