From 07583b6f967a4ce6a1e766decdc77e1015e51fd4 Mon Sep 17 00:00:00 2001
From: Simon Gardling <titaniumtown@proton.me>
Date: Sat, 2 May 2026 20:07:12 -0400
Subject: [PATCH] steamos: disable steam deck cmdlineConfig for non-steamdeck
 hosts

---
 hosts/patiodeck/default.nix | 6 ++++++
 modules/desktop-jovian.nix  | 9 +++++++++
 2 files changed, 15 insertions(+)

diff --git a/hosts/patiodeck/default.nix b/hosts/patiodeck/default.nix
index cdaef83..5dcb0d2 100644
--- a/hosts/patiodeck/default.nix
+++ b/hosts/patiodeck/default.nix
@@ -35,4 +35,10 @@
   ];
 
   jovian.devices.steamdeck.enable = true;
+
+  # opt back into the SteamOS kernel cmdline (amd_iommu=off, lockup_timeout,
+  # sched_hw_submission=4, dcdebugmask=0x20000, ttm.pages_min, audit=0).
+  # desktop-jovian.nix defaults this to false to keep the Deck-tuned amdgpu
+  # params off RDNA3 desktops (yarn); patiodeck IS a Deck so it wants them.
+  jovian.steamos.enableDefaultCmdlineConfig = true;
 }
diff --git a/modules/desktop-jovian.nix b/modules/desktop-jovian.nix
index 7210ee5..439892f 100644
--- a/modules/desktop-jovian.nix
+++ b/modules/desktop-jovian.nix
@@ -31,6 +31,15 @@
     user = username;
   };
 
+  # default off: jovian's SteamOS kernel cmdline (Valve's Deck-tuned amdgpu
+  # params: amd_iommu=off, amdgpu.sched_hw_submission=4, dcdebugmask=0x20000,
+  # lockup_timeout=5000,...,5000, ttm.pages_min=2097152, audit=0) is tuned for
+  # Van Gogh / Sephiroth APUs at 1280x800 and corrupts host memory pages on
+  # RDNA3 desktop GPUs (yarn: Navi 32 1440p, FH5 wine-log showed >1M
+  # illegal-instruction faults across .text after extended play).
+  # mkDefault so actual Deck hosts can opt back in (see hosts/patiodeck).
+  jovian.steamos.enableDefaultCmdlineConfig = lib.mkDefault false;
+
   # jovian overrides the display manager; sddm is required
   services.displayManager.sddm.wayland.enable = true;