SUNXI_MMC_CMD
MMC_WRITE(sc, SUNXI_MMC_CMD, cmdval | cmd->c_opcode);
MMC_WRITE(sc, SUNXI_MMC_CMD, cmd);
if (!(MMC_READ(sc, SUNXI_MMC_CMD) & SUNXI_MMC_CMD_START))
MMC_READ(sc, SUNXI_MMC_CMD));