Add wink patch for disabling MHI M2 state. Rename firmware.

Disabling the MHI M2 state appears to completely resolve issues where
enabling the wifi firmware would cause the the whole system to freeze
quite frequently. The reason for why this fix works so well is still
unknown and under investigation. See some discussion here:

http://lists.infradead.org/pipermail/ath11k/2020-December/000876.html

Also renames the firmware package to clarify that it is for the wifi
driver. This is to avoid confusion with the bluetooth firmware which
will be added in an upcoming patch.

dell/xps/13-9310/default.nix

@@ -7,12 +7,12 @@
 
   # TODO: upstream to NixOS/nixpkgs
   nixpkgs.overlays = [(final: previous: {
-    qca6390-firmware = final.callPackage ./qca6390-firmware.nix {};
+    qca6390-wifi-firmware = final.callPackage ./qca6390-wifi-firmware.nix {};
   })];
 
   hardware.firmware = lib.mkBefore [
     # Firmware for the AX500 (wi-fi & bluetooth chip).
-    pkgs.qca6390-firmware
+    pkgs.qca6390-wifi-firmware
   ];
 
   # The QCA6390 driver currently requires a specific version of the kernel
@@ -212,14 +212,22 @@
             };
           }
 
-          # Patch for crash by w1nk.
+          # Extra patches by wink.
           {
+            # Improves some cases in which races could occur.
             name = "w1nk-irq-lock-patch";
             patch = pkgs.fetchpatch {
               url = "https://raw.githubusercontent.com/w1nk/ath11k-debug/master/one-irq-manage.patch";
               sha256 = "011db3h10smqy0ni0qr9mkyhykf1f3yq6yym6ysbb7jr7l51q0n9";
             };
           }
+          {
+            # System crashes appear to have been caused by MHI state transitions to M2 state.
+            # Currently under investigation.
+            # http://lists.infradead.org/pipermail/ath11k/2020-December/000876.html
+            name = "w1nk-disable-mhi-m2-transition";
+            patch = ./disable-mhi-m2.patch;
+          }
         ];
       } // (args.argsOverride or { }));
     linux_patched = pkgs.callPackage linux_patched_pkg { };

dell/xps/13-9310/disable-mhi-m2.patch

@@ -0,0 +1,19 @@
+diff --git a/drivers/bus/mhi/core/pm.c b/drivers/bus/mhi/core/pm.c
+index 3de7b1639ec6..02882038e4cc 100644
+--- a/drivers/bus/mhi/core/pm.c
++++ b/drivers/bus/mhi/core/pm.c
+@@ -55,12 +55,12 @@ static struct mhi_pm_transitions const dev_state_transitions[] = {
+ 	},
+ 	{
+ 		MHI_PM_M0,
+-		MHI_PM_M0 | MHI_PM_M2 | MHI_PM_M3_ENTER |
++        MHI_PM_M0 | MHI_PM_M3_ENTER |
+ 		MHI_PM_SYS_ERR_DETECT | MHI_PM_SHUTDOWN_PROCESS |
+ 		MHI_PM_LD_ERR_FATAL_DETECT | MHI_PM_FW_DL_ERR
+ 	},
+ 	{
+-		MHI_PM_M2,
++        MHI_PM_M0,
+ 		MHI_PM_M0 | MHI_PM_SYS_ERR_DETECT | MHI_PM_SHUTDOWN_PROCESS |
+ 		MHI_PM_LD_ERR_FATAL_DETECT
+ 	},

dell/xps/13-9310/qca6390-wifi-firmware.nix

@@ -3,7 +3,7 @@
 { stdenv, fetchFromGitHub }:
 
 stdenv.mkDerivation rec {
-  name = "${target}-firmware-${version}";
+  name = "${target}-wifi-firmware-${version}";
   version = "${branch}-00042";
   branch = "master";
   target = "QCA6390";