From 51e4bdf379659e4f80afaa81deea821c48977058 Mon Sep 17 00:00:00 2001
From: Karolis Stasaitis <contact@carlossless.io>
Date: Tue, 2 Aug 2022 20:32:29 +0200
Subject: [PATCH] raspberry-pi-4: add i2c clock-frequency option

---
 raspberry-pi/4/i2c.nix | 50 ++++++++++++++++++++++++++++++++----------
 1 file changed, 39 insertions(+), 11 deletions(-)

diff --git a/raspberry-pi/4/i2c.nix b/raspberry-pi/4/i2c.nix
index 93c1c6d..786581e 100644
--- a/raspberry-pi/4/i2c.nix
+++ b/raspberry-pi/4/i2c.nix
@@ -2,7 +2,8 @@
 
 let
   cfg = config.hardware.raspberry-pi."4";
-  simple-overlay = { target, status }: {
+  optionalProperty = name: value: lib.optionalString (value != null) "${name} = <${builtins.toString value}>;";
+  simple-overlay = { target, status, frequency }: {
     name = "${target}-${status}-overlay";
     dtsText = ''
       /dts-v1/;
@@ -13,6 +14,7 @@ let
           target = <&${target}>;
           __overlay__ {
             status = "${status}";
+            ${optionalProperty "clock-frequency" frequency}
           };
         };
       };
@@ -21,26 +23,52 @@ let
 in
 {
   options.hardware.raspberry-pi."4" = {
-    i2c0.enable = lib.mkEnableOption ''
-      Turn on the VideoCore I2C bus (maps to /dev/i2c-22) and enable access from the i2c group.
-      After a reboot, i2c-tools (e.g. i2cdetect -F 22) should work for root or any user in i2c.
-    '';
-    i2c1.enable = lib.mkEnableOption ''
-      Turn on the ARM I2C bus (/dev/i2c-1 on GPIO pins 3 and 5) and enable access from the i2c group.
-      After a reboot, i2c-tools (e.g. i2cdetect -F 1) should work for root or any user in i2c.
-    '';
+    i2c0 = {
+      enable = lib.mkEnableOption ''
+        Turn on the VideoCore I2C bus (maps to /dev/i2c-22) and enable access from the i2c group.
+        After a reboot, i2c-tools (e.g. i2cdetect -F 22) should work for root or any user in i2c.
+      '';
+      frequency = lib.mkOption {
+        type = lib.types.nullOr lib.types.int;
+        default = null;
+        description = ''
+          interface clock-frequency
+        '';
+      };
+    };
+    i2c1 = {
+      enable = lib.mkEnableOption ''
+        Turn on the ARM I2C bus (/dev/i2c-1 on GPIO pins 3 and 5) and enable access from the i2c group.
+        After a reboot, i2c-tools (e.g. i2cdetect -F 1) should work for root or any user in i2c.
+      '';
+      frequency = lib.mkOption {
+        type = lib.types.nullOr lib.types.int;
+        default = null;
+        description = ''
+          interface clock-frequency
+        '';
+      };
+    };
   };
   config.hardware = lib.mkMerge [
     (lib.mkIf cfg.i2c0.enable {
       i2c.enable = lib.mkDefault true;
       deviceTree = {
-        overlays = [ (simple-overlay { target = "i2c0if"; status = "okay"; }) ];
+        overlays = [ (simple-overlay {
+          target = "i2c0if";
+          status = "okay";
+          frequency = cfg.i2c0.frequency;
+        }) ];
       };
     })
     (lib.mkIf cfg.i2c1.enable {
       i2c.enable = lib.mkDefault true;
       deviceTree = {
-        overlays = [ (simple-overlay { target = "i2c1"; status = "okay"; }) ];
+        overlays = [ (simple-overlay {
+          target = "i2c1";
+          status = "okay";
+          frequency = cfg.i2c1.frequency;
+        }) ];
       };
     })
   ];