linux/debian/patches/patchset-zen/sauce/0008-ZEN-intel-pstate-Implement-enable-parameter.patch

From 48c8812a4cea0190a037757589443f3103c610ba Mon Sep 17 00:00:00 2001
From: Steven Barrett <steven@liquorix.net>
Date: Wed, 15 Jan 2020 20:43:56 -0600
Subject: ZEN: intel-pstate: Implement "enable" parameter

If intel-pstate is compiled into the kernel, it will preempt the loading
of acpi-cpufreq so you can take advantage of hardware p-states without
any friction.

However, intel-pstate is not completely superior to cpufreq's ondemand
for one reason.  There's no concept of an up_threshold property.

In ondemand, up_threshold essentially reduces the maximum utilization to
compare against, allowing you to hit max frequencies and turbo boost
from a much lower core utilization.

With intel-pstate, you have the concept of minimum and maximum
performance, but no tunable that lets you define, maximum frequency
means 50% core utilization.  For just this oversight, there's reasons
you may want ondemand.

Lets support setting "enable" in kernel boot parameters.  This lets
kernel maintainers include "intel_pstate=disable" statically in the
static boot parameters, but let users of the kernel override this
selection.
---
 Documentation/admin-guide/kernel-parameters.txt | 3 +++
 drivers/cpufreq/intel_pstate.c                  | 2 ++
 2 files changed, 5 insertions(+)

--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2254,6 +2254,9 @@
 			disable
 			  Do not enable intel_pstate as the default
 			  scaling driver for the supported processors
+			enable
+			  Enable intel_pstate in-case "disable" was passed
+			  previously in the kernel boot parameters
                         active
                           Use intel_pstate driver to bypass the scaling
                           governors layer of cpufreq and provides it own
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -3817,6 +3817,8 @@ static int __init intel_pstate_setup(cha
 
 	if (!strcmp(str, "disable"))
 		no_load = 1;
+	else if (!strcmp(str, "enable"))
+		no_load = 0;
 	else if (!strcmp(str, "active"))
 		default_driver = &intel_pstate;
 	else if (!strcmp(str, "passive"))