How to enable cache in TMS320C674X?

For register CSL based implementation 

You can enable cache on C674x by configuring the L1 and L2 cache and enabling the MAR bits. An example that shows cache enabled implementation of the FFT function  is described in the QuickStartOMAPL1x_rCSL that can be found here

http://processors.wiki.ti.com/index.php/QuickStartOMAPL1x_rCSL

For BIOS based implementation:

If you are using BIOS 5.x, you can refer to the C6000 BIOS Application Programming interface reference guide for APIs to manage cahce. The BIOS PSP package also shows how you can enable cache while using BIOS device drivers

http://software-dl.ti.com/dsps/dsps_public_sw/psp/BIOSPSP/01_30_00_06/index_FDS.html

Best Regards,

Rahul