sharing DDR3 physical adresses between ARM and DSP??

hello all;

i am using EVMK2H12 with linux ARM.

Actually i want to create a variable in a specific physical adress in DDR3 using  C language in ARM (like 0xA0000000) . but i don't have any idea how to do that.

then read this value with DSP . it is a kind of synchronisation between ARM and DSP in real time. 

because the code that i execute in DSP waits for a specific value of this variable before starting processing. and its the ARM who should write that value in this physical adress.

thank you.