---

было:
#define __NOCACHE	__attribute__((__section__("nocache")))
K_MEM_SLAB_DEFINE_STATIC(mem_slab, BLOCK_SIZE, BLOCK_COUNT, 4);

сделаю так:
#define __NOCACHE	__attribute__((__section__("__dtcm_noinit_section")))
K_MEM_SLAB_DEFINE_IN_SECT_STATIC(mem_slab, __dtcm_noinit_section, BLOCK_SIZE, BLOCK_COUNT, 4);