1. We are running at 24MHz, so it's not possible to run our device faster than this speed.
2. Most FLASH devices are usually not that picky when it comes to timing for CS and the last bit of data on the bus.
3. You are only doing 2 function calls within a few microseconds - You do a RW and do a GPIO set output high and 10 instructions in between.
4. Did you start off with spi_comm_master.c ?
5. Final comment - Please look at the FLASH datasheet and make sure of the timing of the CS line - What FLASH are you using?