[for 26.04_linux-nvidia]: ACPI/cpufreq: CPPC autonomous mode and register handling improvements

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

Documentation/admin-guide/kernel-parameters.txt

@@ -1052,6 +1052,19 @@ Kernel parameters
 			policy to use. This governor must be registered in the
 			kernel before the cpufreq driver probes.
 
+	cppc_cpufreq.auto_sel_mode=
+			[CPU_FREQ] Enable ACPI CPPC autonomous performance
+			selection. When enabled, hardware automatically adjusts
+			CPU frequency on all CPUs based on workload demands.
+			In Autonomous mode, Energy Performance Preference (EPP)
+			hints guide hardware toward performance (0x0) or energy
+			efficiency (0xff).
+			Requires ACPI CPPC autonomous selection register support.
+			Format: <bool>
+			Default: 0 (disabled)
+			0: use cpufreq governors
+			1: enable if supported by hardware
+
 	cpu_init_udelay=N
 			[X86,EARLY] Delay for N microsec between assert and de-assert
 			of APIC INIT to start processors.  This delay occurs

Documentation/cpu-freq/cpu-drivers.rst

@@ -114,8 +114,14 @@ Then, the driver must fill in the following values:
 |policy->cur			    | The current operating frequency of   |
 |				    | this CPU (if appropriate)		   |
 +-----------------------------------+--------------------------------------+
-|policy->min,			    |					   |
-|policy->max,			    |					   |
+|policy->min			    | If set by the driver in ->init(),    |
+|				    | used as initial minimum frequency	   |
+|				    | QoS request.			   |
++-----------------------------------+--------------------------------------+
+|policy->max			    | If set by the driver in ->init(),    |
+|				    | used as initial maximum frequency	   |
+|				    | QoS request.			   |
++-----------------------------------+--------------------------------------+
 |policy->policy and, if necessary,  |					   |
 |policy->governor		    | must contain the "default policy" for|
 |				    | this CPU. A few moments later,       |