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@nvidia.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Pierre Gondois <pierre.gondois@arm.com>
Reviewed-by: Lifeng Zheng <zhenglifeng1@huawei.com>
Link: https://patch.msgid.link/20260206142658.72583-8-sumitg@nvidia.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 3a05604c21bf8d533ca576e81b74f2b19a426b3a..82d10d556cc89f14ee019e6dcc308cccaba07016 100644 (file)
--- 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@vger.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