Re: IP30: SMP, Almost there?

[Joshua Kinard <kumba@gentoo.org>]

On 05/23/2015 23:17, Joshua Kinard wrote:
> On 05/18/2015 01:39, Joshua Kinard wrote:
>> So I've gotten the second CPU in Octane to "tick" again...somehow.  I am
>> certain someone's cat went missing in the process...
> 
> So, yeah, the problem appears to be specific to the R14000 CPU module.  I
> swapped in an R12K dual CPU module, and after a little bit of tinkering to
> revert a few hacks and clean up the code, it boots into SMP, mounts the
> userland, and has successfully sync'ed a Gentoo Portage tree w/o annihilating
> the XFS filesystem or the MD RAID5 array.  Even compiled a few C files.
> 
[snip]
> 
> I even got the IRQs to be fanned out across both CPUs.  Well, primarily the
> qla1280 drivers.  They randomly hop between both CPUs, but no ill effects so far.
> 
> But if I boot that *same* working kernel on an R14000 dual module, I get handed
> an IBE as soon as the userland mounts.  The only documented differences that I
> can find on the R14000 is that it supports DDR memory, being able to do memory
> operations on the rising edge and falling edge of each clock.  Not sure if that
> matters to the kernel at all, but I know of nothing else that describes the
> R14K's internals, such as if there's some new bit in CP0 config,
> branch-diagnostic, status, etc, that might explain why these IBE's are happening.
> 
> Guess I need to hunt down my old dual R10K module next and verify that works
> fine...
> 
> Also, is there a way to hardcode the cca=5 setting for IP30?  Maybe it needs to
> be a hidden Kconfig item?.  I tried setting cpu->writecombine in cpu-probe.c,
> but no dice there.  If I boot an SMP kernel on dual R12K's w/o cca=5, I'll get
> one or two pretty-specific oopses.  The one I did grab complains about bad
> spinlock magic in the core tty driver somewhere.  I can transcribe that oops
> later on if interested.

So far, the problem looks to have been blindly assigning all 64 HEART IRQs to
'handle_level_irq', including the SMP IPI IRQs.  I fixed that by assigning the
four IPI IRQs and four unused debug IRQs to 'handle_percpu_irq'.  So far, no
bus errors, even on R14000.  Also successfully tested 16KB PAGE_SIZE and no bus
errors.  Next, 64KB PAGE_SIZE w/ CONFIG_TRANSPARENT_HUGEPAGE, which was pretty
good at triggering bus errors.

</jinx>

--J