Re: [PATCH v2 13/29] arm_mpam: Probe the hardware features resctrl supports

Jonathan Cameron
2025-09-11T15:30:02Z

On Wed, 10 Sep 2025 20:42:53 +0000
James Morse <james.morse@arm.com> wrote:

> Expand the probing support with the control and monitor types
> we can use with resctrl.
>
> CC: Dave Martin <Dave.Martin@arm.com>
> Signed-off-by: James Morse <james.morse@arm.com>

A few trivial things inline.
LGTM
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Out of time for today, fingers crossed I can get to the others tomorrow.

J
> static int mpam_msc_hw_probe(struct mpam_msc *msc)
> {
> u64 idr;
> @@ -592,6 +736,7 @@ static int mpam_msc_hw_probe(struct mpam_msc *msc)
> mutex_lock(&msc->part_sel_lock);
> idr = mpam_msc_read_idr(msc);
> mutex_unlock(&msc->part_sel_lock);
> +
Stray change - push it to earlier patch.

> msc->ris_max = FIELD_GET(MPAMF_IDR_RIS_MAX, idr);
>
> /* Use these values so partid/pmg always starts with a valid value */
> @@ -614,6 +759,12 @@ static int mpam_msc_hw_probe(struct mpam_msc *msc)
> mutex_unlock(&mpam_list_lock);
> if (IS_ERR(ris))
> return PTR_ERR(ris);
> + ris->idr = idr;
> +
> + mutex_lock(&msc->part_sel_lock);
> + __mpam_part_sel(ris_idx, 0, msc);
> + mpam_ris_hw_probe(ris);
> + mutex_unlock(&msc->part_sel_lock);
> }
>
> spin_lock(&partid_max_lock);
> diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
> index 4cc44d4e21c4..5ae5d4eee8ec 100644
> --- a/drivers/resctrl/mpam_internal.h
> +++ b/drivers/resctrl/mpam_internal.h
> @@ -112,6 +112,55 @@ static inline void mpam_mon_sel_lock_init(struct mpam_msc *msc)
> raw_spin_lock_init(&msc->_mon_sel_lock);
> }
>
> +/*
> + * When we compact the supported features, we don't care what they are.
> + * Storing them as a bitmap makes life easy.
> + */
> +typedef u16 mpam_features_t;

Maybe use a bitmap type and avoid the need to be careful on sizing etc?

> +
> +/* Bits for mpam_features_t */
> +enum mpam_device_features {
> + mpam_feat_ccap_part = 0,
> + mpam_feat_cpor_part,
> + mpam_feat_mbw_part,
> + mpam_feat_mbw_min,
> + mpam_feat_mbw_max,
> + mpam_feat_mbw_prop,
> + mpam_feat_msmon,
> + mpam_feat_msmon_csu,
> + mpam_feat_msmon_csu_capture,
> + mpam_feat_msmon_csu_hw_nrdy,
> + mpam_feat_msmon_mbwu,
> + mpam_feat_msmon_mbwu_capture,
> + mpam_feat_msmon_mbwu_rwbw,
> + mpam_feat_msmon_mbwu_hw_nrdy,
> + mpam_feat_msmon_capt,
> + MPAM_FEATURE_LAST,

If it's always meant to be LAST, I'd drop the trailing comma.

> +};
> +static_assert(BITS_PER_TYPE(mpam_features_t) >= MPAM_FEATURE_LAST);