linux-kernel - Re: [PATCH v3 21/29] arm_mpam: Probe and reset the rest of the features

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Message-ID: <1e48c5ac-d409-47ba-ab59-78a8710d2d15@arm.com>
Date: Mon, 20 Oct 2025 18:16:58 +0100
From: Ben Horgan <ben.horgan@....com>
To: James Morse <james.morse@....com>, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-acpi@...r.kernel.org
Cc: 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,
 Jonathan Cameron <jonathan.cameron@...wei.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>, Jeremy Linton <jeremy.linton@....com>,
 Gavin Shan <gshan@...hat.com>, Zeng Heng <zengheng4@...wei.com>
Subject: Re: [PATCH v3 21/29] arm_mpam: Probe and reset the rest of the
 features

Hi James,

On 10/17/25 19:56, James Morse 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>
> Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>
> Tested-by: Fenghua Yu <fenghuay@...dia.com>
> ---
> Changes since v2:
>  * Moved some enum definitions in here.
>  * Whitespace.
> 
[...]
> diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
> index 2f2a7369107b..00edee9ebc6c 100644
> --- a/drivers/resctrl/mpam_internal.h
> +++ b/drivers/resctrl/mpam_internal.h
> @@ -139,16 +139,30 @@ static inline void mpam_mon_sel_lock_init(struct mpam_msc *msc)
>  
>  /* Bits for mpam features bitmaps */
>  enum mpam_device_features {
> -	mpam_feat_cpor_part = 0,

Any reason this one doesn't stay first?

> +	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_FEATURE_LAST
> +	mpam_feat_partid_nrw,
> +	MPAM_FEATURE_LAST,

nit: drop the trailing , from MPAM_FEATURE_LAST. It confuses the diff.

>  };
>  


-- 
Thanks,

Ben