Can improve time read/write modifying the libnfc driver?

Hello,

I'm testing a PN532 reader using SPI interface over Raspberry Pi and I would like to decrease the read/write.
In my tests,I notice no improvement giving greater priority to process application. I notice some improvement if I change the port speed, but above 3.9MHz the reader is not detected.

Can I change something in the bus/spi.c or driver/pn532_spi.c files? Maybe trim some delay times produced by the selection of each CS (cs= and CS1).

Any suggestion wil be apreciated so much.

Thansk