REG_DESC_WRITE
writel_relaxed(lower_32_bits(addr), ad->base + REG_DESC_WRITE(channo));
writel_relaxed(upper_32_bits(addr), ad->base + REG_DESC_WRITE(channo));
writel_relaxed(tx->period_len, ad->base + REG_DESC_WRITE(channo));
writel_relaxed(FLAG_DESC_NOTIFY, ad->base + REG_DESC_WRITE(channo));