From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 296123A7597; Mon, 21 Sep 2026 19:47:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790020043; cv=none; b=IaYK6rxvfmRkJB6huPXBjnXSI+Cf+6TRL3Js7PMktpaogHBNZqCu8jXlxvqKksjnbIIz6o5jDwNi0cs5iZughiI4ieC+eoW/6bLb80ilcASBJZfHAE1u/1Cn3qyRm1S7qrZc7xwP/78vhz65C/hwxXLBBOltLc3Xk3rBpPFO7t4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790020043; c=relaxed/simple; bh=BcnEdl8QDnPqGivNaUv7+XCrZTH93GaYtfPRvDAlIUc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=TnZ0+yxBMp1AF0cc6kA0mSy2rSG2YN1CrJGjhH4AvKsPV/xKnTGHKMy8cOFKzpMAeNw1o9/uVjGSQpCjZ1iM6k0VG1DO8DqgyctdlN8Wsc3THS4nncJyVoJZIRTK4/2DiOogeom7rMHFT8BC8H/P8dKXyF8C4xIVUlVO5RorceI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=nz8FspN0; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="nz8FspN0" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 97E3D19F6; Mon, 21 Sep 2026 12:47:16 -0700 (PDT) Received: from [10.57.75.12] (unknown [10.57.75.12]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7769F3F86C; Mon, 21 Sep 2026 12:47:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1790020040; bh=BcnEdl8QDnPqGivNaUv7+XCrZTH93GaYtfPRvDAlIUc=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=nz8FspN0pLBCdbpMaLV6xXFKibR6EyNm0OYxDS1JWJv0pGrc01MsCyANO9tYHfF20 SYOxqilDpslCPZDQoPtPIyY2/Q1GMDfkPcGbuGznjqfgonX1i4i5ivEEUvNz3t2KhA 7sSj9y8X06NV8QYcNCILO3VHs8gbhL0+iezIPg0U= Message-ID: <651d6392-984e-4363-8ef6-94a23be615d7@arm.com> Date: Mon, 21 Sep 2026 20:47:15 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 0/3] cpufreq: cppc: Handle Highest Performance changes at runtime To: Jie Zhan , Xueqin Luo , Sudeep Holla , Greg Kroah-Hartman , "Rafael J . Wysocki" , Danilo Krummrich , Viresh Kumar Cc: Lifeng Zheng , Pierre Gondois , Sumit Gupta , linux-kernel@vger.kernel.org, driver-core@lists.linux.dev, linux-pm@vger.kernel.org, Ionela Voinescu References: <20260807060848.832929-1-luoxueqin@kylinos.cn> Content-Language: en-US From: Christian Loehle In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/7/26 09:49, Jie Zhan wrote: > > > On 8/7/2026 2:08 PM, Xueqin Luo wrote: >> Hi Rafael, Pierre, >> >> This series adds support for handling ACPI CPPC Highest Performance >> register changes at runtime, triggered by Notify(0x85) on a processor >> device. >> >> When the platform changes the Highest Performance value (e.g. due to >> thermal or power budget adjustments), the OSPM must re-evaluate the >> cached capability and propagate the change to the cpufreq policy, >> the scheduler's CPU capacity model, and the frequency invariance >> engine. > Any real use case of this on platforms that run cppc_cpufreq drivers? > Some addtional motivation may help. > > For example, a processor can age over time and its core frequency degrades. > It's good if platforms can make OSPM and userspace aware of this. +1 If this is still current then I'd love to see a resend with a fix to affect the entire policy at once, not just policy->cpu and I'd propose for now also limiting highest_perf at first probe and ignoring any highest_perf_new > highest_perf, until we have a compelling case / platform that uses it, because IMO it does make everything more complicated. (+CC Ionela) > [snip]