wiiu/audio: Open device in new thread

AX initialization needs to be done on CPU1, otherwise interrupts won't be handled properly.
Previously this was attmpted to be done using `OSSetThreadAffinity` to change the affinity of the current thread.
Unfortunately `OSSetThreadAffinity` does not work when called for the currently running thread.
This caused issues when an SDL audio device was opened from a thread not running on CPU1.
This commit now creates a new thread running on CPU1 for AX initialization, and joins it before moving on.

Author: GaryOderNichts

src/audio/wiiu/SDL_wiiuaudio.c

@@ -61,13 +61,11 @@ static SDL_AudioDevice* cb_this;
 /*  +1, but never goes above NUM_BUFFERS */
 #define next_id(id) (id + 1) % NUM_BUFFERS
 
-static int WIIUAUDIO_OpenDevice(_THIS, const char* devname) {
-    int ret = 0;
+static int _WIIUAUDIO_OpenDeviceFunction(_THIS) {
     AXVoiceOffsets offs;
     AXVoiceVeData vol = {
         .volume = 0x8000,
     };
-    uint32_t old_affinity;
     float srcratio;
     Uint8* mixbuf = NULL;
     uint32_t mixbuf_allocation_count = 0;
@@ -80,10 +78,6 @@ static int WIIUAUDIO_OpenDevice(_THIS, const char* devname) {
 
     SDL_zerop(this->hidden);
 
-/*  We *must not* change cores when setting stuff up */
-    old_affinity = OSGetThreadAffinity(OSGetCurrentThread());
-    OSSetThreadAffinity(OSGetCurrentThread(), AX_MAIN_AFFINITY);
-
 /*  Take a quick aside to init the wiiu audio */
     if (!AXIsInit()) {
     /*  Init the AX audio engine */
@@ -147,8 +141,7 @@ static int WIIUAUDIO_OpenDevice(_THIS, const char* devname) {
 
     if (!mixbuf) {
         printf("Couldn't allocate mix buffer\n");
-        ret = SDL_OutOfMemory();
-        goto end;
+        return SDL_OutOfMemory();
     }
 
     memset(mixbuf, 0, this->spec.size * NUM_BUFFERS);
@@ -163,8 +156,7 @@ static int WIIUAUDIO_OpenDevice(_THIS, const char* devname) {
     if (this->hidden->deintvbuf == NULL) {
         AXQuit();
         printf("DEBUG: Couldn't allocate deinterleave buffer");
-        ret = SDL_SetError("Couldn't allocate deinterleave buffer");
-        goto end;
+        return SDL_SetError("Couldn't allocate deinterleave buffer");
     }
 
 
@@ -174,8 +166,7 @@ static int WIIUAUDIO_OpenDevice(_THIS, const char* devname) {
         if (!this->hidden->voice[i]) {
             AXQuit();
             printf("DEBUG: couldn't get voice\n");
-            ret = SDL_OutOfMemory();
-            goto end;
+            return SDL_OutOfMemory();
         }
 
     /*  Start messing with it */
@@ -247,10 +238,64 @@ static int WIIUAUDIO_OpenDevice(_THIS, const char* devname) {
     cb_this = this; //wish there was a better way
     AXRegisterAppFrameCallback(_WIIUAUDIO_framecallback);
 
-end: ;
-/*  Put the thread affinity back to normal - we won't call any more AX funcs */
-    OSSetThreadAffinity(OSGetCurrentThread(), old_affinity);
-    return ret;
+    return 0;
+}
+
+static void _WIIUAUDIO_ThreadDeallocator(OSThread *thread, void *stack) {
+   free(thread);
+   free(stack);
+}
+
+static void _WIIUAUDIO_ThreadCleanup(OSThread *thread, void *stack) {
+}
+
+static int WIIUAUDIO_OpenDevice(_THIS, const char *devname) {
+    int result;
+
+    /* AX functions need to run from the same core.
+       Since we cannot easily change the affinity of the currently running thread, we create a new one if necessary.
+       This thread only runs on CPU1 (AX_MAIN_AFFINITY) and will be joined after initialization is done. */
+    if (OSGetThreadAffinity(OSGetCurrentThread()) != AX_MAIN_AFFINITY) {
+        OSThread *thread;
+        uint32_t stackSize = 32 * 1024;
+        uint8_t *stack;
+        int32_t priority = OSGetThreadPriority(OSGetCurrentThread());
+
+        thread = (OSThread *)memalign(16, sizeof(OSThread));
+        if (!thread) {
+            return SDL_OutOfMemory();
+        }
+
+        stack = memalign(16, stackSize);
+        if (!stack) {
+            free(thread);
+            return SDL_OutOfMemory();
+        }
+
+        if (!OSCreateThread(thread,
+                            (OSThreadEntryPointFn)_WIIUAUDIO_OpenDeviceFunction,
+                            (int32_t)this,
+                            NULL,
+                            stack + stackSize,
+                            stackSize,
+                            priority,
+                            AX_MAIN_AFFINITY))
+        {
+            return SDL_SetError("OSCreateThread() failed");
+        }
+
+        OSSetThreadDeallocator(thread, &_WIIUAUDIO_ThreadDeallocator);
+        OSSetThreadCleanupCallback(thread, &_WIIUAUDIO_ThreadCleanup);
+        OSResumeThread(thread);
+
+        if (!OSJoinThread(thread, &result)) {
+            return SDL_SetError("OSJoinThread() failed");
+        }
+    } else {
+        result = _WIIUAUDIO_OpenDeviceFunction(this);
+    }
+
+    return result;
 }
 
 /*  Called every 3ms before a frame of audio is rendered. Keep it fast! */
@@ -405,7 +450,7 @@ static void WIIUAUDIO_ThreadInit(_THIS) {
     OSSetThreadPriority(currentThread, priority);
 }
 
-static SDL_bool WIIUAUDIO_Init(SDL_AudioDriverImpl* impl) {
+static SDL_bool WIIUAUDIO_Init(SDL_AudioDriverImpl *impl) {
     impl->OpenDevice = WIIUAUDIO_OpenDevice;
     impl->PlayDevice = WIIUAUDIO_PlayDevice;
     impl->WaitDevice = WIIUAUDIO_WaitDevice;