Re: Ingenic JZ4730 - illegal instruction

["Kevin D. Kissell" <kevink@paralogos.com>]

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Nils Faerber wrote:
> Kevin D. Kissell schrieb:
>   
>> Are you sure that the JZ_RISC section is in fact the version of those
>> functions that's being built into your kernel?
>>     
>
> Well, there is CONFIG_JZRISC=y in the kernel .config and a
> switch(current_cpu_type) { case CPU_JZRISC: ...} so I would assume it is
> being used. But I will verify that the CONFIG_JZRISC=y is correctly
> translated into a current_cpu_type.
>   
Your assumption is reasonable.  But given that things aren't working, 
yes, it's good to verify.
> Oh, one last question, in order to rule out the cache as bug-spot would
> the kernel option "run uncached" "solve" the issue (and be darn slow)?
>   
It would certainly solve the issue, and would *probably* result in a 
system that would be fully functional but slow.  Very high end and very 
low end systems can be rendered unusable by forcing uncached operation, 
but it's certainly worth a try.  Also, if your cache control logic 
supports both write-back and write-through operation, if you set the 
default cache "attribute" for kernel and page tables (which is 
essentially what you're doing under-the-hood when you configure for 
uncached operation) to write-through, that should cure the problems with 
copying text pages, but *not* those with re-using them, with less 
performance impact.  I'd be a little surprised if the Ingenic part 
offered both modes, though.

          Regards,

          Kevin K.

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