mmc_test_seq_perf
ret = mmc_test_seq_perf(test, write, 10 * SZ_1M, 1);
ret = mmc_test_seq_perf(test, write, 100 * SZ_1M, 1);
ret = mmc_test_seq_perf(test, write, 1000 * SZ_1M, 1);