linux-kernel - Re: [RFC PATCH 13/36] arm_mpam: Add probe/remove for mpam msc driver and kbuild boiler plate

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Message-ID: <13398823-bcef-4bda-a6ea-c5ccde49ef6a@arm.com>
Date: Wed, 6 Aug 2025 19:03:23 +0100
From: James Morse <james.morse@....com>
To: Ben Horgan <ben.horgan@....com>, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org
Cc: Rob Herring <robh@...nel.org>, Rohit Mathew <rohit.mathew@....com>,
 Shanker Donthineni <sdonthineni@...dia.com>, Zeng Heng
 <zengheng4@...wei.com>, Lecopzer Chen <lecopzerc@...dia.com>,
 Carl Worth <carl@...amperecomputing.com>,
 shameerali.kolothum.thodi@...wei.com,
 D Scott Phillips OS <scott@...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>, Rex Nie <rex.nie@...uarmicro.com>,
 Dave Martin <dave.martin@....com>, Koba Ko <kobak@...dia.com>
Subject: Re: [RFC PATCH 13/36] arm_mpam: Add probe/remove for mpam msc driver
 and kbuild boiler plate

Hi Ben,

On 24/07/2025 12:02, Ben Horgan wrote:
> On 11/07/2025 19:36, James Morse wrote:
>> Probing MPAM is convoluted. MSCs that are integrated with a CPU may
>> only be accessible from those CPUs, and they may not be online.
>> Touching the hardware early is pointless as MPAM can't be used until
>> the system-wide common values for num_partid and num_pmg have been
>> discovered.
>>
>> Start with driver probe/remove and mapping the MSC.

>> diff --git a/drivers/platform/arm64/mpam/mpam_devices.c b/drivers/platform/arm64/mpam/
>> mpam_devices.c
>> new file mode 100644
>> index 000000000000..5b886ba54ba8
>> --- /dev/null
>> +++ b/drivers/platform/arm64/mpam/mpam_devices.c
>> @@ -0,0 +1,336 @@

>> +static int mpam_dt_count_msc(void)
>> +{
>> +    int count = 0;
>> +    struct device_node *np;
>> +
>> +    for_each_compatible_node(np, NULL, "arm,mpam-msc")

> This will count even 'status = "disabled"' nodes. Add a check for that.
> 
> if (of_device_is_available(np))> +        count++;

Good spot, fixed - thanks.


Thanks,

James


>> +
>> +    return count;
>> +}