Re: IP30: SMP, Almost there?

[Joshua Kinard <kumba@gentoo.org>]

On 06/01/2015 15:32, Ralf Baechle wrote:
> 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

It's cca=3 as the default.  Wasn't there a patch long ago that made that the
default?

                       D
              I   D    S     S   S  B S S  E   P  P C D   K
              C   C  0 D 0   C   S  E K B  C   M  E T N   0
             -----------------------------------------------
             xxx xxx x x xx xxx xxx x x x xxxx xx x x xx xxx
0x6c1ab3a3   011 011 0 0 00 011 010 1 0 1 1001 11 0 1 00 011    no cca
0x6c1ab3a5   011 011 0 0 00 011 010 1 0 1 1001 11 0 1 00 101    cca=5


I think cca=4 also works okay, but I have to test it a bit more.  Which is the
better one to stick with?

--J