MAX_DESC
if (unlikely((tx->num_desc == (MAX_DESC - 1)))) {
tx->desc_limit = MAX_DESC;
if (unlikely(tx->num_desc == MAX_DESC))
descp = kmalloc_objs(struct sdma_desc, MAX_DESC, GFP_ATOMIC);
tx->desc_limit = MAX_DESC - 1;
tx->desc_limit = MAX_DESC;