rz_dmac_ch_readl
chstat = rz_dmac_ch_readl(channel, CHSTAT, 1);
ret = read_poll_timeout(rz_dmac_ch_readl, chstat, !(chstat & CHSTAT_EN),
chstat = rz_dmac_ch_readl(channel, CHSTAT, 1);
chctrl = rz_dmac_ch_readl(channel, CHCTRL, 1);