Re: IP30: SMP, Almost there?

[Ralf Baechle <ralf@linux-mips.org>]

On Sat, May 23, 2015 at 11:17:25PM -0400, Joshua Kinard wrote:

> 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.

Can you insert something like:

  printk("c0_config: %08x\n", read_c0_config());

into a kernel and boot it without cca=5?  I'm really curious what the
startup CCA is.

  Ralf