linux-kernel - Re: [PATCH v2 21/29] arm_mpam: Probe and reset the rest of the features

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Message-ID: <20250912140702.00000a5a@huawei.com>
Date: Fri, 12 Sep 2025 14:07:02 +0100
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>,
	<linux-acpi@...r.kernel.org>, D Scott Phillips OS
	<scott@...amperecomputing.com>, <carl@...amperecomputing.com>,
	<lcherian@...vell.com>, <bobo.shaobowang@...wei.com>,
	<tan.shaopeng@...itsu.com>, <baolin.wang@...ux.alibaba.com>, Jamie Iles
	<quic_jiles@...cinc.com>, Xin Hao <xhao@...ux.alibaba.com>,
	<peternewman@...gle.com>, <dfustini@...libre.com>, <amitsinght@...vell.com>,
	David Hildenbrand <david@...hat.com>, Dave Martin <dave.martin@....com>, Koba
 Ko <kobak@...dia.com>, Shanker Donthineni <sdonthineni@...dia.com>,
	<fenghuay@...dia.com>, <baisheng.gao@...soc.com>, Rob Herring
	<robh@...nel.org>, Rohit Mathew <rohit.mathew@....com>, "Rafael Wysocki"
	<rafael@...nel.org>, Len Brown <lenb@...nel.org>, Lorenzo Pieralisi
	<lpieralisi@...nel.org>, Hanjun Guo <guohanjun@...wei.com>, Sudeep Holla
	<sudeep.holla@....com>, Catalin Marinas <catalin.marinas@....com>, "Will
 Deacon" <will@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Danilo Krummrich <dakr@...nel.org>, Zeng Heng <zengheng4@...wei.com>
Subject: Re: [PATCH v2 21/29] arm_mpam: Probe and reset the rest of the
 features

On Wed, 10 Sep 2025 20:43:01 +0000
James Morse <james.morse@....com> wrote:

> MPAM supports more features than are going to be exposed to resctrl.
> For partid other than 0, the reset values of these controls isn't
> known.
> 
> Discover the rest of the features so they can be reset to avoid any
> side effects when resctrl is in use.
> 
> PARTID narrowing allows MSC/RIS to support less configuration space than
> is usable. If this feature is found on a class of device we are likely
> to use, then reduce the partid_max to make it usable. This allows us
> to map a PARTID to itself.
> 
> CC: Rohit Mathew <Rohit.Mathew@....com>
> CC: Zeng Heng <zengheng4@...wei.com>
> CC: Dave Martin <Dave.Martin@....com>
> Signed-off-by: James Morse <james.morse@....com>

A few trivial things inline.

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

>  int mpam_register_requestor(u16 partid_max, u8 pmg_max)
>  {
>  	int err = 0;
> @@ -667,10 +676,35 @@ static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
>  	struct mpam_msc *msc = ris->vmsc->msc;
>  	struct device *dev = &msc->pdev->dev;
>  	struct mpam_props *props = &ris->props;
> +	struct mpam_class *class = ris->vmsc->comp->class;
>  
>  	lockdep_assert_held(&msc->probe_lock);
>  	lockdep_assert_held(&msc->part_sel_lock);
>  
> +	/* Cache Capacity Partitioning */
> +	if (FIELD_GET(MPAMF_IDR_HAS_CCAP_PART, ris->idr)) {
> +		u32 ccap_features = mpam_read_partsel_reg(msc, CCAP_IDR);
> +
> +		props->cmax_wd = FIELD_GET(MPAMF_CCAP_IDR_CMAX_WD, ccap_features);
> +		if (props->cmax_wd &&
> +		    FIELD_GET(MPAMF_CCAP_IDR_HAS_CMAX_SOFTLIM, ccap_features))
> +			mpam_set_feature(mpam_feat_cmax_softlim, props);
> +
> +		if (props->cmax_wd &&
> +		    !FIELD_GET(MPAMF_CCAP_IDR_NO_CMAX, ccap_features))
> +			mpam_set_feature(mpam_feat_cmax_cmax, props);
> +
> +		if (props->cmax_wd &&
> +		    FIELD_GET(MPAMF_CCAP_IDR_HAS_CMIN, ccap_features))
> +			mpam_set_feature(mpam_feat_cmax_cmin, props);
> +
> +		props->cassoc_wd = FIELD_GET(MPAMF_CCAP_IDR_CASSOC_WD, ccap_features);
> +
Trivial but blank line here feels inconsistent with local style. I'd drop it.
> +		if (props->cassoc_wd &&
> +		    FIELD_GET(MPAMF_CCAP_IDR_HAS_CASSOC, ccap_features))
> +			mpam_set_feature(mpam_feat_cmax_cassoc, props);
> +	}
> +

> diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
> index 17570d9aae9b..326ba9114d70 100644
> --- a/drivers/resctrl/mpam_internal.h
> +++ b/drivers/resctrl/mpam_internal.h
> @@ -136,25 +136,34 @@ static inline void mpam_mon_sel_lock_init(struct mpam_msc *msc)
>   * 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;
> +typedef u32 mpam_features_t;

This is strengthening my view that this should just be a DECLARE_BITMAP(MPAM_FEATURE_LAST)
in the appropriate places.

>  
>  /* Bits for mpam_features_t */
>  enum mpam_device_features {
> -	mpam_feat_ccap_part = 0,
> +	mpam_feat_cmax_softlim,
> +	mpam_feat_cmax_cmax,
> +	mpam_feat_cmax_cmin,
> +	mpam_feat_cmax_cassoc,
>  	mpam_feat_cpor_part,
>  	mpam_feat_mbw_part,
>  	mpam_feat_mbw_min,
>  	mpam_feat_mbw_max,
>  	mpam_feat_mbw_prop,
> +	mpam_feat_intpri_part,
> +	mpam_feat_intpri_part_0_low,
> +	mpam_feat_dspri_part,
> +	mpam_feat_dspri_part_0_low,
>  	mpam_feat_msmon,
>  	mpam_feat_msmon_csu,
>  	mpam_feat_msmon_csu_capture,
> +	mpam_feat_msmon_csu_xcl,
>  	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_feat_partid_nrw,
>  	MPAM_FEATURE_LAST,
>  };
>  static_assert(BITS_PER_TYPE(mpam_features_t) >= MPAM_FEATURE_LAST);
> @@ -165,6 +174,10 @@ struct mpam_props {
>  	u16			cpbm_wd;
>  	u16			mbw_pbm_bits;
>  	u16			bwa_wd;
> +	u16			cmax_wd;
> +	u16			cassoc_wd;
> +	u16			intpri_wd;
> +	u16			dspri_wd;
>  	u16			num_csu_mon;
>  	u16			num_mbwu_mon;
>  };