This family of uControllers has serveral and grave bugs related with the SDRAM controller. If you plan to use SDRAM you only can do that configuring the uC in a 32 bit bus wide fashion.
If you plan to use only one 16 bits (most standard) SDRAM chip, you have to use it in a Big endian mode. That is not the best way of using an embedded Linux because the standard and most tested versions (of the OS and the toolchains) are in Little endian mode.
This is only an overview of some errors, I attach the whole errata sheet. Please read it carefully before select this family of devices for your project.
The errata sheet that I attach is for the TMS5471 uC but the similar errors are inside the TMS5470 and the TMS5472 (the problems are for the whole family).