Hello again,
well i didn't get any responses at all to my last post so I thought i'd try
this again.
I have kernel 2.4.26 installed on a Xilinx XUP board and everything works well
except I can't seem to communicate with peripherals on the OPB or PLB bus
through devfs. devfs is on and mounted and everything, and I'm able open a
file handle to it w/ the following code:
int main (int argc, char *argv[]) {
int fd;
int *ptr;
fd = open("/dev/mem", O_RDWR);
if(fd == -1) {
printf("Err: cannot open /dev/mem\n");
return -1;
}
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 = 0xA0000000;
...
mmap also seems to work, and returns a virtual address that is supposed to
point to the location in physical memory at USER_LOGIC_BASEADDR. when I try to
use ptr, however, I either get
bus error
or
do_wp_page: bogus page at address 3001a000 (page 0xc2c4c004)
VM: killing process led_test.o
depending on whether I use MAP_SHARED or MAP_PRIVATE.
These errors occur if I try to access any device on either PLB or OPB - even
the OPB UART (which i KNOW is working). This technique DOES work, however, for
address ranges in RAM. This indicates to me that it's some sort of higher
level memory management problem w/ linuxppc such that it doesn't realize these
address ranges are valid. I assume this is a function of the BSP that gets
generated in EDK? Anybody have any idea how I can tell linux to let me use
these addresses? Any other thoughts?
If I'm being too vague or something please let me know and I'll resolve it
immediately...
Thanks much, --scott
Other details:
linuxppc-2.4.26
busybox 1.1.0
powerpc-405-linux-gnu-gcc 3.4.1
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