AXI_DMAC_REG_X_LENGTH
axi_dmac_write(dmac, AXI_DMAC_REG_X_LENGTH, 0xffffffff);
chan->max_length = axi_dmac_read(dmac, AXI_DMAC_REG_X_LENGTH);
axi_dmac_write(dmac, AXI_DMAC_REG_X_LENGTH, 0x00);
axi_dmac_read(dmac, AXI_DMAC_REG_X_LENGTH);
axi_dmac_write(dmac, AXI_DMAC_REG_X_LENGTH, sg->hw->x_len);
case AXI_DMAC_REG_X_LENGTH: