[coreboot] Exception on Skylake after enabling ACPI timer emulation

[Nico Huber]

Hello Piotr,

On 17.05.2018 18:20, Banik, Subrata wrote:
>>> FSP2.0, I'm following Librem Purism options since they seem to boot the
>>> same SoC. They use KabyLake FSP obtained by get_blobss.sh [1], if you
>>> think this is incorrect then I would like to know why, because it may
>>> mean that Pursim code is also incorrect from Intel point of view.
> 
> SKL won't be compatible with KBL FSP. Please don’t try to use KBL FSP
> and mix match with SKL Coreboot. No one tested that combination. 

Unless FSP is calling home, we can't say anything about the actual test
coverage. KBL FSP somehow works on SKL. I assume the code is written for
both platforms, the binaries are usually just not validated for all SKUs
supported by the code (and it's often not documented for which they were
validated).

I wouldn't be surprised if the KBL FSP was more tested on SKL by now;
not by Intel but by their customers and individuals. There's one simple
reason: The older SKL FSP lacks most of the configuration options and
is not well maintained within coreboot. So the KBL FSP works better (but
you don't get any guarantee for that). OTOH, the KBL FSP release on
GitHub is also not well integrated (although it was released half a year
later, it's way behind regarding the header files in coreboot). The only
Kabylake FSP binary 100% compatible with coreboot is the Google Support
Package (not published separately, but you can carve it out of their
firmware images).

To wrap it up, if you want a public FSP binary that was validated for
SKL, you'll have to use the old FSP1.1 version; or push Intel to publish
something new. I would talk to your Intel support contact in any case,
sometimes binaries pop up that nobody knew about.

Nico

PS. I can confirm that the KabylakeFsp0001 drop from last summer works
    with a 25W SKL-S CPU. Judging from the commit date, I also run it
    with that MSR write applied.