[Skiboot] [PATCH v10 08/17] core/pci: Option for serialized jobs

Stewart Smith stewart at linux.vnet.ibm.com
Fri May 13 14:31:21 AEST 2016

Gavin Shan <gwshan at linux.vnet.ibm.com> writes:
> On Fri, May 13, 2016 at 10:33:27AM +1000, Stewart Smith wrote:
>>Gavin Shan <gwshan at linux.vnet.ibm.com> writes:
>>> Currently, the PHB reset and PCI enumeration are done concurrently
>>> on multiple CPU cores. The output messages are interleaved and not
>>> readable enough. This adds a option to do the jobs in serialized
>>> fashion for debugging purpose only. The serialized mode should be
>>> always disabled in field.
>>> Signed-off-by: Gavin Shan <gwshan at linux.vnet.ibm.com>
>>I think we could accomplish this in the generic code a lot neater, in
>>core/cpu.c __cpu_queue_job() we could just add:
>>if (cpu == NULL)
>>   cpu = this_cpu();
>>and then we'd be automatically able to pretty easily enable serializing
>>of things that would otherwise happen in parallel.
>>(better than ifdef may be something in debug descriptor... although
>>setting that on boot before things start executing may be casually fun)
> Good idea. Thanks, Stewart. It will be included into next revision.
> The side-effect is to affect all paths including PCI enumeration. As
> it's for debugging, I guess it's not a problem.

There's likely other uses for it too, so for debug it's fine. Will be
just like booting with GA1 skiboot :)

> Yeah, debug descriptor should be better. I'm not sure if it has
> been supported in skiboot and how it can be enabled?

Likely need a define to make it the default rather than something
selectable at runtime - otherwise you have to be able to change the
contents of host memory in between skiboot load and starting to execute
it, which isn't always possible.

Stewart Smith
OPAL Architect, IBM.

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