It's good to at least know that this doesn't seem to be a kernel
issue, and thanks for the strace advice (I am new to this level of
linux development). Here is the truncated output for devmem and the
minimal example:
--- devmem ---
open("/dev/mem", O_RDWR|O_SYNC) = 3
fstat64(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 0), ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1,
0) = 0x4001f000
write(1, "/dev/mem opened.\n", 17) = 17
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_SHARED, 3, 0x48088) = 0x40020000
write(1, "Memory mapped at address 0x40020"..., 37) = 37
write(1, "Value at address 0x48088024 (0x4"..., 46) = 46
munmap(0x40020000, 4096) = 0
close(3) = 0
io_submit(0, 0, 0xfbad2088 <unfinished ... exit status 0>
Process 1635 detached
--minimal python example--
open("/dev/mem", O_RDWR|O_SYNC|O_LARGEFILE) = 3
fstat64(3, {st_mode=S_IFCHR|0640, st_rdev=makedev(1, 1), ...}) = 0
dup(3) = 4
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_SHARED, 3, 0x48088) = 0x40020000
--- SIGBUS (Bus error) @ 0 (0) ---
+++ killed by SIGBUS +++
Process 1633 detached
It looks like python decided to add a O_LARGEFILE and duplicate the
file descriptor. I'm still not sure what's going on here that's
causing the problem as both mmap2 calls are identical.
I don't mean to bombard this list with a problem that isn't related to
the kernel, so I'll post this to a python list somewhere. Thanks a
million for your help so far, this is driving me nutty! Also if any
more info would help just let me know.
On Tue, Oct 20, 2009 at 7:26 PM, Paul Walmsley <paul@xxxxxxxxx> wrote:
> On Tue, 20 Oct 2009, Brett Graham wrote:
>
>> If I run the following commads:
>> devmem2 0x48004a40 w 0x0000038a # select 32kHz clock
>> devmem2 0x48004a10 w 0x03007052 # enable iclk for gpt11
>> devmem2 0x48004a00 w 0x03007000 # enable fclk for gpt11
>>
>> which all run sensibly and alter the registers, then I try to previous
>> minimum example on address 0x48088024 (TCLK for gpt11) I get the
>> following error:
>> Unhandled fault: external abort on non-linefetch (0x1018) at 0x40020024
>> Bus error
>>
>> What puzzles me is that when I use devmem2 to read or write to the
>> same register, everything works fine.
>
> Consider running strace on devmem2 and comparing it to the strace of your
> Python code? That should show you any differences. If devmem2 works,
> it's unlikely to be a kernel problem.
>
>
> - Paul
>
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