oprofile callgraph support missing for common cpus

[Andy Fleming]

On Nov 17, 2011, at 11:30 AM, Maynard Johnson wrote:

>> 
>> Notice the first
>> 		 if (!cur_cpu_spec->oprofile_cpu_type)
>> 		 		 return -ENODEV;
>> 
>> 		 if (firmware_has_feature(FW_FEATURE_ISERIES))
>> 		 		 return -ENODEV;
>> For my e300c2 cpu both if's are false and I don't get support for callgraph/backtrace
>> support. Moving the ops->backtrace = op_powerpc_backtrace; to the top
>> enables backtrace for me.
> What kernel version are you using?  Actually, looking at a 3.0.3 tree I happen to have available, I see oprofile h/w event support (in arch/powerpc/kernel/cputable.c) for e300c3 and e300c4, but not the other e300 flavors.  I've added Andy Flemming from Freescale to cc.  Maybe he knows why e300c2 isn't supported.

e300c2 does not have hardware performance monitor events.

However, it should be able to support timer-based profiling, right? And why not support backtrace from there? Do we require hardware counters to get a backtrace?

Andy