Hey all, I'm currently bringing up Linux on a Xilinx XUP demo board and I could use some assistance. For those who are unfamiliar, the XUP has a Virtex II Pro with 2 hard-core PPC405 processors. I have been following the EMPART tutorial to get things going
I have the basic system up and running and things look good EXCEPT: I can not seem to map into a custom IP hanging off the OPB bus. Actually, I can't manage to communicate with any peripherals at all off the OPB bus.
As per the EMPART tutorial's recommendations, here's how I attempt IP access:
fd = open("/dev/mem", O_RDWR); ptr = MAP_FAILED; // Initialize to bad value ptr = (int *) mmap(0, 256, PROT_READ|PROT_WRITE, MAP_SHARED, fd, USER_LOGIC_BASEADDR);
if(ptr==MAP_FAILED) { printf("Err: cannot access address!\n"); return -1; }
*ptr = 0xA;
The mmap call appears to work, and returns a pointer to virtual memory that supposedly references the physical address my IP is located at. However, when I try to read or write to this pointer I just get a rather ambiguous "bus error".
In attempt to diagnose the problem, I have tried simple file i/o calls to /dev/mem via the fd variable specifically lseek and read() / write(). These also fail. lseek works, but then when I try to read or write it returns 0.
It is noteworthy, however, that when I make a stand-alone project in Xilinx EDK and acces my custom IP from there everything works fine.
So, anyone have any suggestions? Could this have to do w/ the PPC405's MMU or something? Anyone have any experience here?
Thanks much for your help,
--scott