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

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Message-ID: <aQMrONyVjGsCFXe2@gmail.com>
Date: Thu, 30 Oct 2025 10:09:12 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Zide Chen <zide.chen@...el.com>
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


* 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.)

(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