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

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Message-ID: <600dc476-6922-4cd5-b3e3-ef10cd38085e@nvidia.com>
Date: Sat, 4 Oct 2025 17:53:18 -0700
From: Fenghua Yu <fenghuay@...dia.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>,
 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>
Subject: Re: [PATCH v2 13/29] arm_mpam: Probe the hardware features resctrl
 supports


On 9/10/25 13:42, James Morse wrote:
> Expand the probing support with the control and monitor types
> we can use with resctrl.
>
> CC: Dave Martin <Dave.Martin@....com>
> Signed-off-by: James Morse <james.morse@....com>

Reviewed-by: Fenghua Yu <fenghuay@...dia.com>

A couple of minor comments below.

> ---
> Changes since v1:
>   * added an underscore to a variable name.
>
> Changes since RFC:
>   * Made mpam_ris_hw_probe_hw_nrdy() more in C.
>   * Added static assert on features bitmap size.
> ---
>   drivers/resctrl/mpam_devices.c  | 151 ++++++++++++++++++++++++++++++++
>   drivers/resctrl/mpam_internal.h |  53 +++++++++++
>   2 files changed, 204 insertions(+)
>
> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
> index a26b012452e2..ba8e8839cdc4 100644
> --- a/drivers/resctrl/mpam_devices.c
> +++ b/drivers/resctrl/mpam_devices.c
[SNIP]
> @@ -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);
> +

Adding this blank line is irrelevant to this patch. It's better to move 
this blank line to the original patch #11.

>   	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;
> +

mpam_features_t is changed to u32 later in patch #21. It's better to 
directly define it as u32 here and remove the type change in patch #21.

[SNIP]

Thanks.

-Fenghua