From 4dc56db37e32dcfecd667ebbf88263e47b296097 Mon Sep 17 00:00:00 2001
From: Alex Ivanov <gnidorah@users.noreply.github.com>
Date: Mon, 26 Dec 2016 12:41:59 +0300
Subject: [PATCH] cpu-freq: Try powersave if ondemand is not available

---
 nixos/modules/config/power-management.nix |  4 ++--
 nixos/modules/tasks/cpu-freq.nix          | 17 +++++++++++------
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/nixos/modules/config/power-management.nix b/nixos/modules/config/power-management.nix
index fbd7867a0953..d4d8b22eae44 100644
--- a/nixos/modules/config/power-management.nix
+++ b/nixos/modules/config/power-management.nix
@@ -69,8 +69,8 @@ in
 
   config = mkIf cfg.enable {
 
-    # FIXME: Implement powersave governor for sandy bridge or later Intel CPUs
-    powerManagement.cpuFreqGovernor = mkDefault "ondemand";
+    # ondemand governor is not available on sandy bridge or later Intel CPUs
+    powerManagement.cpuFreqGovernor = mkDefault [ "ondemand" "powersave" ];
 
     systemd.targets.post-resume = {
       description = "Post-Resume Actions";
diff --git a/nixos/modules/tasks/cpu-freq.nix b/nixos/modules/tasks/cpu-freq.nix
index 5f8b5df52acf..c559bb78f070 100644
--- a/nixos/modules/tasks/cpu-freq.nix
+++ b/nixos/modules/tasks/cpu-freq.nix
@@ -13,9 +13,9 @@ in
   options = {
 
     powerManagement.cpuFreqGovernor = mkOption {
-      type = types.nullOr types.str;
-      default = null;
-      example = "ondemand";
+      type = types.listOf types.str;
+      default = [];
+      example = [ "ondemand" ];
       description = ''
         Configure the governor used to regulate the frequence of the
         available CPUs. By default, the kernel configures the
@@ -28,9 +28,9 @@ in
 
   ###### implementation
 
-  config = mkIf (!config.boot.isContainer && config.powerManagement.cpuFreqGovernor != null) {
+  config = mkIf (!config.boot.isContainer && config.powerManagement.cpuFreqGovernor != []) {
 
-    boot.kernelModules = [ "cpufreq_${cfg.cpuFreqGovernor}" ];
+    boot.kernelModules = map (x: "cpufreq_" + x) cfg.cpuFreqGovernor;
 
     environment.systemPackages = [ cpupower ];
 
@@ -43,7 +43,12 @@ in
       serviceConfig = {
         Type = "oneshot";
         RemainAfterExit = "yes";
-        ExecStart = "${cpupower}/bin/cpupower frequency-set -g ${cfg.cpuFreqGovernor}";
+        ExecStart = ''
+          ${pkgs.bash}/bin/sh -c \
+          "for i in ${toString cfg.cpuFreqGovernor}; do \
+            ${cpupower}/bin/cpupower frequency-set -g $i && break; \
+          done"
+        '';
         SuccessExitStatus = "0 237";
       };
     };