Depending on what you want to do. I usually program the FPGA as a memory device and connect it directly to the main DSP bus. As a result, the FPGA will look like anyother memory / devices that connect to the DSP.
I will not recommend using the HPI in this case. Most of the time HPI is used to interface to a micro-controller. It is not necessary to use it for FPGA. (Of course, you can if you want to.)
If you don't know how to connect the FPGA, look up how to connect an SRAM for your DSP and examine the interface timing. Then design your FPGA to look just like the SRAM. I am sure you can find App notes on how to connect an SRAM to your DSP.
with regard to the Analog device you mentioned, check out the section in the Sharc user manual relating to host interface, all the details are clearly shown and it can be achieved with a FPGA.
using TMS320C5510 and virtex2. you can interface thru EMIF of dsp, where FPGA is configured to be seen as static memory space, or thru McBSP serially if suitable.