lv2: Reimplement sys_timer_usleep

- Matches ps3 accuracy for all tested values with few exceptions
- Do not enter the host OS kernel if waiting for less than 500us to avoid scheduler issues

rpcs3/Emu/Cell/lv2/sys_sync.h

@@ -122,6 +122,12 @@ struct lv2_obj
 		sleep_timeout(thread, timeout);
 	}
 
+	static void yield(cpu_thread& thread)
+	{
+		vm::temporary_unlock(thread);
+		awake(thread, -4);
+	}
+
 	// Schedule the thread
 	static void awake(cpu_thread&, u32 prio);
 

rpcs3/Emu/Cell/lv2/sys_timer.cpp

@@ -294,14 +294,28 @@ error_code sys_timer_usleep(ppu_thread& ppu, u64 sleep_time)
 
 	sys_timer.trace("sys_timer_usleep(sleep_time=0x%llx)", sleep_time);
 
-	u64 passed = 0;
+	if (sleep_time)
-
-	lv2_obj::sleep(ppu, std::max<u64>(1, sleep_time));
-
-	while (sleep_time >= passed)
 	{
-		thread_ctrl::wait_for(std::max<u64>(1, sleep_time - passed));
+		u64 passed = 0;
-		passed = get_system_time() - ppu.start_time;
+		u64 remaining;
+
+		lv2_obj::sleep(ppu, sleep_time);
+
+		while (sleep_time > passed)
+		{
+			remaining = sleep_time - passed;
+
+			if (remaining > 500)
+				thread_ctrl::wait_for(remaining - (remaining % 500));
+			else
+				busy_wait(4000);
+
+			passed = (get_system_time() - ppu.start_time);
+		}
+	}
+	else
+	{
+		lv2_obj::yield(ppu);
 	}
 
 	return CELL_OK;