[Bug 93956] Display Port BYT-M [N2807] - Data link training fails sporadically

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=93956

--- Comment #7 from Ville Syrjala <ville.syrjala at linux.intel.com> ---
(In reply to Zoran Stojsavljevic from comment #6)
> Hello OTC team,
> 
> Today, as I have promised, Werner Zeh from Siemens MC came to IMU
> Feldkirchen, to work with me together on the DDI Port C BYT-M (N2807)
> issue/bug. 
> 
> The following we did, in order to close to the potential FW problem and to
> find the Root Cause of this problem.
> [1] I did use my BBAY Fab. 3 CRB, swapping E3826 (two core BYT-I) with issue
> infested N2807 BYT-M. The reballed "bad" N2807 worked immediately with BBAY
> Fab. 3.
> [2] Once I had problematic N2807, I did verify all the parameters from CCG
> internal BIOS X64.A093.R42 I have build, to check the validity of this BIOS.
> [3] The BIOS shows correct 0x30678 N2807 BYT-M CPUID, as well as the latest
> used MCU 833.
> [4] The BIOS implemented (assembled by me) appears to be UEFI compliant
> BIOS, 64 bit one, visually checked with version, as well as with .efi 32/64
> size checker.
> [5] With this BIOS (X64.A093.R42) it is IMPOSSIBLE to experience/show this
> issue with EMGD vBIOS 3909, as well as with GOP 7.2.1013 (used Fedora 23,
> kernel 4.3.5-300.fc23.x86_64)!
> [6] Then we switch gears to FSP MR4/MR5 (irrelevant, both work the same
> way), and single channel N2807 does expose/show this issue very clearly.
> [7] There was investigation going on, so we concluded that something in FSP
> is not either initialized accordingly with UEFI BIOS, or there is time
> de-synchronization.
> [8] I set this use case according to INTEL rules to prove this issue on BBAY
> Fab.3 CRB, with FSP used.
> [9] I have BBAY Fab.3 CRB with N2807 and FSP as real prove that we, INTEL,
> have the problem!
> 
> Now... I am just wondering if anything can/could be done from OTC/booting
> kernel levels, so some additional registers can be initialized by i915
> driver to solve this issue (it is clear that issue comes from legacy
> BIOS/FSP levels, which does not necessarily mean that it could not be fixed
> by Linux kernel using i915 GFX driver). 

First, what is FSP?

And second, we're still waiting for that debug log Jani requested.

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