dell: add xps 9570

dell/xps/15-9570/README.wiki

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+= Dell XPS 15 9570 =
+
+== Tested Hardware ==
+
+* CPU: Intel(R) Core(TM) i7-8750H CPU @ 2.20GHz
+* RAM: 32 GB
+* HDD: 256 GiB SSD
+* Screen: 15" 4k (3840✕2160)
+* Graphics: NVIDIA Corporation GP107M, with Intel Graphics too.
+* Input: Touchscreen and trackpad.
+
+
+== Firmware Configuration ==
+
+Not much tweaking of NixOS itself was needed. But we currently cannot automate the firmware setup, so this must be done by hand.
+
+=== Before installation ===
+
+These settings are needed both for booting the final install, and installer itself. Therefore, they must be done first.
+
+* ''Disable Secure Boot (but keep UEFI Boot).'' Thankfully doing so is as easy as changing any other simple setting.
+
+* ''Disable Intel hardware RAID and use AHCI instead.'' Intel doesn't seem to provide a working linux driver for this.  (If you just have SSD it's pointless and just slows things down needlessly anyways.)
+
+
+=== After installation ===
+
+* ''Add systemd-boot to UEFI boot list.'' The (uneditable anyways) settings mapping drive UUIDs to HD* work fine.
+
+=== Optional ===
+
+* ''Update BIOS.'' According to Reddit, this helps with battery life.
+
+* ''Update Intel's Thunderbolt firmware.'' Without this, the Thunderbolt port will only work as power source, and not transfer data.
+
+=== Troubleshooting ===

dell/xps/15-9570/default.nix

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+{ lib, ... }:
+
+{
+  imports = [
+    ../../../common/cpu/intel
+    ../../../common/pc/laptop
+  ];
+
+  # TODO: boot loader
+  boot.loader.systemd-boot.enable = lib.mkDefault true;
+  boot.loader.efi.canTouchEfiVariables = lib.mkDefault true;
+
+  nix.buildCores = lib.mkDefault 12;
+
+  # Recommended in Arch wiki, avoids shutdowns
+  boot.kernelParams = [
+    "mem_sleep_default=deep"
+    "nouveau.blacklist=0"
+    "acpi_osi=!"
+    "acpi_osi=\"Windows 2015\""
+    "acpi_backlight=vendor"
+  ];
+
+  # To just use Intel integrated graphics with Intel's open source driver
+  # hardware.nvidiaOptimus.disable = true;
+
+  # To setup proprietary NVIDIA Optimus properly.
+  # boot.blacklistedKernelModules = [ "nouveau" "nv" "rivafb" "nvidiafb" "rivatv" ];
+  # services.xserver.videoDrivers = [ "nvidia" ];
+  # hardware.nvidia.optimus_prime.enable = true;
+  # hardware.nvidia.modesetting.enable = true;
+
+  # This should be the same for all XPS 9570 models with NVIDIA
+  hardware.nvidia.optimus_prime = {
+    intelBusId = "PCI:0:2:0";
+    nvidiaBusId = "PCI:1:0:0";
+  };
+}