linux-kernel - Re: [PATCH v6 4/9] ACPI: CPPC: Add cppc_get_perf() API to read performance controls

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <0ea13064-be34-449c-9dd0-760333111da3@huawei.com>
Date: Thu, 22 Jan 2026 19:42:07 +0800
From: "zhenglifeng (A)" <zhenglifeng1@...wei.com>
To: Pierre Gondois <pierre.gondois@....com>, Sumit Gupta <sumitg@...dia.com>
CC: <rafael@...nel.org>, <viresh.kumar@...aro.org>, <ionela.voinescu@....com>,
	<lenb@...nel.org>, <robert.moore@...el.com>, <corbet@....net>,
	<rdunlap@...radead.org>, <ray.huang@....com>, <gautham.shenoy@....com>,
	<mario.limonciello@....com>, <perry.yuan@....com>, <zhanjie9@...ilicon.com>,
	<linux-pm@...r.kernel.org>, <linux-acpi@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, <acpica-devel@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
	<treding@...dia.com>, <jonathanh@...dia.com>, <vsethi@...dia.com>,
	<ksitaraman@...dia.com>, <sanjayc@...dia.com>, <nhartman@...dia.com>,
	<bbasu@...dia.com>
Subject: Re: [PATCH v6 4/9] ACPI: CPPC: Add cppc_get_perf() API to read
 performance controls

On 2026/1/22 19:30, Pierre Gondois wrote:
> 
> On 1/22/26 09:56, zhenglifeng (A) wrote:
>> On 2026/1/20 22:56, Sumit Gupta wrote:
>>> +
>>> +    if (CPC_SUPPORTED(desired_perf_reg))
>>> +        cpc_read(cpu, desired_perf_reg, &desired_perf);
>>> +    perf_ctrls->desired_perf = desired_perf;
>> desired_perf_reg is not an optional one, so it has to be supported.
> 
> The ACPI spec seems to say it is optional under some circumstances.
> 
> Cf:
> """
> This register is optional when OSPM
> indicates support for CPPC2 in the platform-wide _OSC
> capabilities and the Autonomous Selection Enable reg-
> ister is Integer 1
> """
> 
> 
> Maybe it is ok to let this check here and to a more complex verification
> in acpi_cppc_processor_probe()

Right. My mistake.

>