I recently switch to MQX 4.2 from MQX 4.0 and the USB transfers have slowed considerably.
I modified MQX 4.0 per this link: https://community.freescale.com/thread/320155?q=usb%20transfer , which is changing delay_const in khci.c and USBCFG_DEFAULT_MAX_NAK_COUNT in host_cnfg.h. This sped up the USB transfers. I also did this with MQX 4.2 but it is much slower than 4.0.
I used _time_get_ticks to measure the time to open, write and close files on the USB with the following results:
MQX 4.0 4.2
File open: 70 ms 80 ms
File write: 350 ms 1270 ms
File close: 0 ms 50 ms
How can I modify MQX 4.2 to perform as MQX 4.0 does?