linux-kernel - Re: [PATCH RESEND 1/3] perf/x86/intel/cstate: Add Clearwater Forest support

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Message-ID: <9c21d7e0-fcfd-43c2-ba5d-5881400a46ca@intel.com>
Date: Thu, 30 Oct 2025 10:38:56 -0700
From: "Chen, Zide" <zide.chen@...el.com>
To: Ingo Molnar <mingo@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Andi Kleen <ak@...ux.intel.com>, Eranian Stephane <eranian@...gle.com>,
 linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
 Dapeng Mi <dapeng1.mi@...ux.intel.com>, Xudong Hao <xudong.hao@...el.com>,
 Falcon Thomas <thomas.falcon@...el.com>,
 Artem Bityutskiy <artem.bityutskiy@...el.com>,
 Kan Liang <kan.liang@...ux.intel.com>, Zhenyu Wang <zhenyuw.linux@...il.com>
Subject: Re: [PATCH RESEND 1/3] perf/x86/intel/cstate: Add Clearwater Forest
 support



On 10/30/2025 2:09 AM, Ingo Molnar wrote:
> 
> * Zide Chen <zide.chen@...el.com> wrote:
> 
>> Clearwater Forest is based on the Darkmont Atom microarchitecture.
>> From the perspective of C-state residency profiling, it supports the
>> same residency counters as Sierra Forest: CC1/CC6, PC2/PC6, and MC6.
>>
>> Please note that the C1E residency counter can only be read via PMT,
>> not MSR. Therefore, tools relying on the perf_event framework cannot
>> access the C1E residency.
>>
>> Cc: Artem Bityutskiy <artem.bityutskiy@...el.com>
>> Reviewed-by: Kan Liang <kan.liang@...ux.intel.com>
>> Signed-off-by: Zhenyu Wang <zhenyuw.linux@...il.com>
>> Signed-off-by: Zide Chen <zide.chen@...el.com>
> 
> So, this is not a valid SOB chain: primary author should be the first 
> SOB, or if it was co-developed, it should have the proper 
> Co-developed-by tags.
> 
> Here I can see two possibilities:
> 
> (1) if Zhenyu Wang was the primary author, and Zide Chen reviewed, 
>     tested and submitted it upstream, then:
> 
> 
>   | From: Zide Chen <zide.chen@...el.com>
>   | Subject: [PATCH 1/3] perf/x86/intel/cstate: Add Clearwater Forest support
> 
>     From: Zhenyu Wang <zhenyuw.linux@...il.com>
>     ...
> 
>     Signed-off-by: Zhenyu Wang <zhenyuw.linux@...il.com>
>     Signed-off-by: Zide Chen <zide.chen@...el.com>
> 
> (I.e. add the extra From line as the first line of the changelog.)

Yes, that is the case.
Thank you very much for pointing this out! I will pay extra attention to
the SoB chain going forward.


> (2) if it was co-developed, with Zhenyu Wang and Zide Chen having each 
>     written unique lines of code of their own that finally resulted in 
>     this submission, then:
> 
>   | From: Zide Chen <zide.chen@...el.com>
>   | Subject: [PATCH 1/3] perf/x86/intel/cstate: Add Clearwater Forest support
> 
>     ...
> 
>     Co-developed-by: Zide Chen <zide.chen@...el.com>
>     Signed-off-by: Zide Chen <zide.chen@...el.com>
>     Co-developed-by: Zhenyu Wang <zhenyuw.linux@...il.com>
>     Signed-off-by: Zhenyu Wang <zhenyuw.linux@...il.com>
> 
> Which one was it? :-)
> 
> Thanks,
> 
> 	Ingo