Initial config. for Lenovo Yoga Slim 7 Pro-X (14ARH7)

- Add entry to README.md and flake.nix

lenovo/yoga/7/14ARH7/default.nix

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+{ config, lib, pkgs, ... }:
+
+let
+  inherit (lib) mkDefault mkMerge;
+
+in {
+  imports = [
+    ../../../../common/cpu/amd
+    # Better power-savings from AMD PState:
+    ../../../../common/cpu/amd/pstate.nix
+    ../../../../common/gpu/amd
+    ## "prime.nix" loads this, aleady:
+    # ../../../../common/gpu/nvidia
+    ../../../../common/gpu/nvidia/prime.nix
+    ../../../../common/pc/laptop
+    ../../../../common/pc/laptop/acpi_call.nix
+    ../../../../common/pc/ssd
+  ];
+
+  config = mkMerge [
+    {
+      # Configure basic system settings:
+      boot = {
+        kernelModules = [ "kvm-amd" ];
+        kernelParams = [
+          "mem_sleep_default=deep"
+          "pcie_aspm.policy=powersupersave"
+
+          ## Supposed to help fix for suspend issues: SSD not correctly working, and Keyboard not responding:
+          ## Not needed for the 6.1+ kernels?
+          # "iommu=pt"
+
+          ## Fixes for s2idle:
+          ##    https://www.phoronix.com/news/More-s2idle-Rembrandt-Linux
+          # "acpi.prefer_microsoft_guid=1"
+          ## Appears to have been renamed?
+          "acpi.prefer_microsoft_dsm_guid=1"
+        ];
+
+        blacklistedKernelModules = [ "nouveau" ];
+      };
+    }
+
+    {
+      ## Graphics settings
+
+      ## AMD RX680
+      # services.xserver.videoDrivers = mkDefault [ "amdgpu" ];
+
+      # NVIDIA GeForce RTX 3050 Mobile (Ampere)
+      services.xserver.videoDrivers = mkDefault [ "nvidia" ];
+
+      hardware = {
+        ## Enable the Nvidia card, as well as Prime and Offload:
+        amdgpu.loadInInitrd = true;
+        opengl.extraPackages = with pkgs; [
+          vaapiVdpau
+          libvdpau-va-gl
+        ];
+
+        nvidia = {
+          modesetting.enable = true;
+          nvidiaSettings = true;
+
+          prime = {
+            offload = {
+              enable = true;
+              enableOffloadCmd = true;
+            };
+            amdgpuBusId = "PCI:4:0:0";
+            nvidiaBusId = "PCI:1:0:0";
+          };
+
+          powerManagement = {
+            enable = true;
+            # finegrained = true
+          };
+        };
+      };
+    }
+  ];
+}