linux-kernel - [PATCH v8 7/7] cpufreq: CPPC: Add sysfs documentation for perf

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Message-ID: <20260206142658.72583-8-sumitg@nvidia.com>
Date: Fri, 6 Feb 2026 19:56:58 +0530
From: Sumit Gupta <sumitg@...dia.com>
To: <rafael@...nel.org>, <viresh.kumar@...aro.org>, <pierre.gondois@....com>,
	<zhenglifeng1@...wei.com>, <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>, <yumpusamongus@...il.com>,
	<dedekind1@...il.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>
CC: <linux-tegra@...r.kernel.org>, <treding@...dia.com>,
	<jonathanh@...dia.com>, <vsethi@...dia.com>, <ksitaraman@...dia.com>,
	<sanjayc@...dia.com>, <nhartman@...dia.com>, <mochs@...dia.com>,
	<bbasu@...dia.com>, <sumitg@...dia.com>
Subject: [PATCH v8 7/7] cpufreq: CPPC: Add sysfs documentation for perf_limited

Add ABI documentation for the Performance Limited Register sysfs
interface in the cppc_cpufreq driver.

Signed-off-by: Sumit Gupta <sumitg@...dia.com>
Reviewed-by: Randy Dunlap <rdunlap@...radead.org>
Reviewed-by: Pierre Gondois <pierre.gondois@....com>
Reviewed-by: Lifeng Zheng <zhenglifeng1@...wei.com>
---
 .../ABI/testing/sysfs-devices-system-cpu       | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 3a05604c21bf..82d10d556cc8 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -327,6 +327,24 @@ Description:	Energy performance preference
 
 		This file is only present if the cppc-cpufreq driver is in use.
 
+What:		/sys/devices/system/cpu/cpuX/cpufreq/perf_limited
+Date:		February 2026
+Contact:	linux-pm@...r.kernel.org
+Description:	Performance Limited
+
+		Read to check if platform throttling (thermal/power/current
+		limits) caused delivered performance to fall below the
+		requested level. A non-zero value indicates throttling occurred.
+
+		Write the bitmask of bits to clear:
+
+		  - 0x1 = clear bit 0 (desired performance excursion)
+		  - 0x2 = clear bit 1 (minimum performance excursion)
+		  - 0x3 = clear both bits
+
+		The platform sets these bits; OSPM can only clear them.
+
+		This file is only present if the cppc-cpufreq driver is in use.
 
 What:		/sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
 Date:		August 2008
-- 
2.34.1