Kconfig: use uncached buffer only for debugging

To rule out buffer coherency issue, it is useful to add a debug option
with which selected only coherent/uncached buffer will be used.

Signed-off-by: Keyon Jie <yang.jie@linux.intel.com>

Kconfig.xtos-dbg

@@ -12,3 +12,12 @@ config DEBUG_BLOCK_FREE
 	  already freed block of memory. Enabling this feature increases
 	  number of memory writes and reads, due to checks for memory patterns
 	  that may be performed on allocation and deallocation.
+
+config DEBUG_FORCE_COHERENT_BUFFER
+	bool "Force the allocator to allocate coherent buffer only"
+	default n
+	help
+	  Select if we want to force the allocator to return coherent/uncached
+	  buffer only.
+	  This should be selected for debug purpose only, as accessing buffer
+	  without caching it will reduce the read/write performance.

src/lib/alloc.c

@@ -921,8 +921,12 @@ static void *_balloc_unlocked(uint32_t flags, uint32_t caps, size_t bytes,
 	if (!ptr)
 		return ptr;
 
+#ifdef	CONFIG_DEBUG_FORCE_COHERENT_BUFFER
+	return cache_to_uncache(ptr);
+#else
 	return (flags & SOF_MEM_FLAG_COHERENT) && (CONFIG_CORE_COUNT > 1) ?
 		cache_to_uncache(ptr) : uncache_to_cache(ptr);
+#endif
 }
 
 /* allocates continuous buffers - not for direct use, clients use rballoc() */