The registers are found in the Technical Reference Manual for the processor. I have a link to the DM3730 manual here: http://www.ti.com/lit/pdf/sprugn4

You will have to register and login to TI. I am not exactly sure what you're trying to do, but Table 13-4 shows the pin is shared with gpio_57.

If you want to pin mux it to CS6, the register to do that is 0x480020B8

If you want to use CS6 as a GPIO, we have a GPIO app note so you can toggle it up and down: http://support.logicpd.co...rtalid=0&EntryId=698

If there is some GPMC specific stuff you are trying to do, section 10 of the reference manual linked above goes into detail on the GPMC bus.