From e6f0a1e7ebceac4e25150384008f5b051aa8be03 Mon Sep 17 00:00:00 2001
From: Atemu <atemu.main@gmail.com>
Date: Sat, 22 Feb 2020 12:43:06 +0100
Subject: [PATCH 1/3] undervolt: apply undervolt on boot and resume

The undervolt did not persist reboots or sleep/hibernation. With this
change you should no longer have to apply the undervolt on a timer
---
 nixos/modules/services/hardware/undervolt.nix | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/nixos/modules/services/hardware/undervolt.nix b/nixos/modules/services/hardware/undervolt.nix
index 828032dc573a..1f1a6d674787 100644
--- a/nixos/modules/services/hardware/undervolt.nix
+++ b/nixos/modules/services/hardware/undervolt.nix
@@ -114,6 +114,11 @@ in
       path = [ pkgs.undervolt ];
 
       description = "Intel Undervolting Service";
+
+      # Apply undervolt on boot, nixos generation switch and resume
+      wantedBy = [ "multi-user.target" "post-resume.target" ];
+      after = [ "post-resume.target" ]; # Not sure why but it won't work without this
+
       serviceConfig = {
         Type = "oneshot";
         Restart = "no";

From ed83bac1d98aa3818331685d968444dbda66dc28 Mon Sep 17 00:00:00 2001
From: Atemu <atemu.main@gmail.com>
Date: Sat, 22 Feb 2020 12:45:47 +0100
Subject: [PATCH 2/3] undervolt: make timer opt-in

It should no longer be needed but is worth keeping around in case it is
---
 nixos/modules/services/hardware/undervolt.nix | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/nixos/modules/services/hardware/undervolt.nix b/nixos/modules/services/hardware/undervolt.nix
index 1f1a6d674787..054ffa35050a 100644
--- a/nixos/modules/services/hardware/undervolt.nix
+++ b/nixos/modules/services/hardware/undervolt.nix
@@ -103,6 +103,17 @@ in
         The temperature target on battery power in Celsius degrees.
       '';
     };
+
+    useTimer = mkOption {
+      type = types.bool;
+      default = false;
+      description = ''
+        Whether to set a timer that applies the undervolt settings every 30s.
+        This will cause spam in the journal but might be required for some
+        hardware under specific conditions.
+        Enable this if your undervolt settings don't hold.
+      '';
+    };
   };
 
   config = mkIf cfg.enable {
@@ -126,7 +137,7 @@ in
       };
     };
 
-    systemd.timers.undervolt = {
+    systemd.timers.undervolt = mkIf cfg.useTimer {
       description = "Undervolt timer to ensure voltage settings are always applied";
       partOf = [ "undervolt.service" ];
       wantedBy = [ "multi-user.target" ];

From f5856db1b83671bae5dc9886f23c3612498a1246 Mon Sep 17 00:00:00 2001
From: Atemu <atemu.main@gmail.com>
Date: Wed, 13 May 2020 10:47:16 +0200
Subject: [PATCH 3/3] rl-2009: add note on undervolt timer changes

---
 nixos/doc/manual/release-notes/rl-2009.xml | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/nixos/doc/manual/release-notes/rl-2009.xml b/nixos/doc/manual/release-notes/rl-2009.xml
index 59a4d78c27e4..592aa3dcaf4d 100644
--- a/nixos/doc/manual/release-notes/rl-2009.xml
+++ b/nixos/doc/manual/release-notes/rl-2009.xml
@@ -910,6 +910,13 @@ services.transmission.settings.rpc-bind-address = "0.0.0.0";
       The packages <package>perl</package>, <package>rsync</package> and <package>strace</package> were removed from <option>systemPackages</option>. If you need them, install them again with <code><xref linkend="opt-environment.systemPackages"/> = with pkgs; [ perl rsync strace ];</code> in your <filename>configuration.nix</filename>.
     </para>
    </listitem>
+   <listitem>
+    <para>
+      The <literal>undervolt</literal> option no longer needs to apply its
+      settings every 30s. If they still become undone, open an issue and restore
+      the previous behaviour using <literal>undervolt.useTimer</literal>.
+    </para>
+   </listitem>
   </itemizedlist>
  </section>
 </section>