srv-core: Add fancontrol

hosts/srv-core/hardware.nix

@@ -1,4 +1,4 @@
-{ inputs, ... }:
+{ config, inputs, ... }:
 {
   imports = [ inputs.nixos-hardware.nixosModules.hardkernel-odroid-h4 ];
 
@@ -10,6 +10,7 @@
       "coretemp"
       "it87"
     ];
+    extraModulePackages = [ config.boot.kernelPackages.it87 ];
     initrd.availableKernelModules = [
       "xhci_pci"
       "ahci"
@@ -41,4 +42,33 @@
       };
     };
   };
+
+  # Ensure pwm2_enable is set to 2 (automatic) before fancontrol starts,
+  # because the IT8613E can't transition 0 -> 1 (manual) directly,
+  # but can do 2 -> 1 which fancontrol requires.
+  systemd.services.fancontrol-pwm-init = {
+    description = "Initialize IT8613E PWM mode for fancontrol";
+    before = [ "fancontrol.service" ];
+    requiredBy = [ "fancontrol.service" ];
+    serviceConfig.Type = "oneshot";
+    script = "echo 2 > /sys/devices/platform/it87.2608/hwmon/hwmon*/pwm2_enable";
+    unitConfig.ConditionPathExists = "/sys/devices/platform/it87.2608";
+  };
+
+  hardware.fancontrol = {
+    enable = true;
+    config = ''
+      INTERVAL=5
+      DEVPATH=hwmon1=devices/platform/coretemp.0 hwmon2=devices/platform/it87.2608
+      DEVNAME=hwmon1=coretemp hwmon2=it8613
+      FCTEMPS=hwmon2/pwm2=hwmon1/temp1_input
+      FCFANS=hwmon2/pwm2=hwmon2/fan2_input
+      MINTEMP=hwmon2/pwm2=70
+      MAXTEMP=hwmon2/pwm2=100
+      MINSTART=hwmon2/pwm2=35
+      MINSTOP=hwmon2/pwm2=25
+      MINPWM=hwmon2/pwm2=0
+      MAXPWM=hwmon2/pwm2=255
+    '';
+  };
 }