[Skiboot] [PATCH] phb4: Add link training trace mode

[Stewart Smith]

Michael Neuling <mikey at neuling.org> writes:
> Add a mode to PHB4 to trace training process closely. This activates
> as soon as PERST is deasserted and produces human readable output of
> the process.
>
> This may increase training times since it duplicates some of the
> training code.  This code has it's own simple checks for fence and
> timeout but will fall through to the default training code once done.
>
> Output produced, looks like the "TRACE:" lines below:
>
>   [    3.410799664,7] PHB#0001[0:1]: FRESET: Starts
>   [    3.410802000,7] PHB#0001[0:1]: FRESET: Prepare for link down
>   [    3.410806624,7] PHB#0001[0:1]: FRESET: Assert skipped
>   [    3.410808848,7] PHB#0001[0:1]: FRESET: Deassert
>   [    3.410812176,3] PHB#0001[0:1]: TRACE: 0x0000000101000000  0ms
>   [    3.417170176,3] PHB#0001[0:1]: TRACE: 0x0000100101000000 12ms presence
>   [    3.436289104,3] PHB#0001[0:1]: TRACE: 0x0000180101000000 49ms training
>   [    3.436373312,3] PHB#0001[0:1]: TRACE: 0x00001d0811000000 49ms trained
>   [    3.436420752,3] PHB#0001[0:1]: TRACE: Link trained.
>   [    3.436967856,7] PHB#0001[0:1]: LINK: Start polling
>   [    3.437482240,7] PHB#0001[0:1]: LINK: Electrical link detected
>   [    3.437996864,7] PHB#0001[0:1]: LINK: Link is up
>   [    4.438000048,7] PHB#0001[0:1]: LINK: Link is stable
>
> Enabled via nvram using:
>   nvram -p ibm,skiboot --update-config pci-tracing=true
>
> Signed-off-by: Michael Neuling <mikey at neuling.org>

Merged to master as of b4c69f3126ecbe85f415d8a6aa06efab80653cbc

-- 
Stewart Smith
OPAL Architect, IBM.