Re: Linux 2.6.39 on Cavium CN38xx

[David Daney <ddaney@caviumnetworks.com>]

On 06/13/2011 08:34 PM, Guenter Roeck wrote:
> On Mon, Jun 13, 2011 at 05:51:11PM -0400, Guenter Roeck wrote:
> [ ... ]
>>>>
>>>> The actual interrupt causing trouble and spurious interrupts in my case is,
>>>> oddly enough, STATUSF_IP0. So far I have been unable to track down how that
>>>> is triggered; I don't see the bit being set set in C0_CAUSE anywhere.
>>>>
>>>> Are there any means to trigger an IP0 interrupt other than by writing STATUSF_IP0
>>>> into the C0_CAUSE register ?
>>>>
>>>
>>> No.  Nothing that I know of ever uses IP0 and IP1, so they should always
>>> be cleared.
>>>
>> Exactly what I figured, yet I still get those spurious interrupts if IP0 is enabled.
>> Something odd is definitely going on in my system.
>>
>> Besides the above, my hopefully final problem is that timer interrupts are only
>> received by CPU 0. Any idea what to look for to fix this problem ?
>>
> Found the problem. Apparently the BIOS resets CvmCtl[IPTI] to 0.

That is clearly erroneous behavior.  Although you can set any value, the 
HRM clearly states that 2..7 are the only legal values.

The Cavuim/Octeon u-boot just leave it at the default value of 7, and 
the kernel basically expects it to be 7, and never explicitly sets it.

We do set the IPPCI to 6 in the kernel, and for performance reasons, 
expect it to have a different value than IPTI.  IP{2,3,4} are basically 
reserved for use by the system interrupt controller, so really these 
things must be on one of IP{5,6,7}.

David Daney