crash when read/write mapped io registers

[torrance2461]

Hi,

I am using mmap() in user space to access SPI registers in the OMAP3530.

The physical address is 0x48098000 (OMAP_MCSPI1_BASE) which is the start of the McSPI1 registers. mmap works fine. But when I try to print out the register values I got

Unhandled fault: external abort on non-linefetch (0x101 at 0x4002100c Bus error

I have seen some posts which had the same issue but I haven't seen any reply or solution to it. Can anyone help please? Any suggestion would be appreciated.



Here is the code:

fd = open("/dev/mem", O_RDWR);
if (fd == -1)
{
printf("open() failed!\n");
return -1;
}

mmap_addr = mmap(NULL, mem_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd,mem_start);
if (mmap_addr == MAP_FAILED) {
printf("gpio mmap() failed!\n");
exit(1);
}

ptr = (unsigned int *)(mmap_addr) ;
printf(" 0x%08x mapped to %p (%p)\n", OMAP_MCSPI1_BASE, mmap_addr, ptr) ;

ptr+=4 ; // skip the first 4 registers and start from SCR register
printf("%p 0x08x\n", ptr, *ptr) ; ptr ++ ;
printf("%p 0x08x\n", ptr, *ptr) ; ptr ++ ;

...

I also tried similar code to map the GPIO registers, it worked fine and I could do read/write with those GPIO registers.



Many thanks.

[Rubberman]

Are you sure that the start address is a multiple of the system page size (usually 4 kbytes)?