I have a MTFC8GLDDQ-4M eMMC NAND flash from Micron and a custom made board with iMX6Q on it.
My system setup is as following:
kernel: 3.10.17 (RT patched) minor boot customization for our board
rootfs: in-house (hard compiled)
toolchain: Linaro gcc 4.7.2
The system is working fine except the high latency in disk I/O, running the command sync can sometime take 4-5 seconds.
I have tried to backport the mmc driver from kernel 4.2 without any success.
I have also tried various RT settings for the mmc/jbd kernel threads and played around with the dirty_ratio and other settings in /proc/sys/vm without any major difference.
Before I go and dive into the driver I liked to ask if this is a known problem or not ?