[Bug 103347] [dp] intel_dp.c:1554 WARN_ON(len <=8)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=103347

--- Comment #15 from shashank.sharma at intel.com <shashank.sharma at intel.com> ---
(In reply to F.Hartung from comment #12)
> I'm pretty sure it uses a LSPCON since I updated the hdmi firmware with this
> tool to 1.72
> (https://downloadcenter.intel.com/download/26609/NUCs-HDMI-2-0-Firmware-
> Update-Tool-for-Intel-NUC-Kit-NUC6CAY-and-NUC7i3BN?product=95069)
> to solve audio issues.
> 
> There is a whole thread about the problems of the Intel Apollo Lake platform
> and others with quite a similar board (J4205-ITX) report they also updated
> their hdmi firmware. 
> https://forum.kodi.tv/showthread.php?tid=270298&pid=2553256#pid2553256
This is a different issue they are talking about, this is about getting HDR 10
bit output using HDMI 2.0 port (LSPCON), whereas this problem seems to be
basic.
> 
> The Apollo Lake boards use a "HDMI-2.0-LSPCon MegaChips MCDP2800", there is
> a similar chip on my board so I'm pretty sure it is an internal DP port
> mapped to the HDMI port.
> 
> http://www.megachips.com/products/displayport/MCDP28x0
MCDP2800 is a DP to HDMI converter LSPCON device, which is on-board with many
APL devices in a motherboard down mode.
> 
> https://www.heise.de/imgs/18/2/2/5/8/6/6/2/MegaChips-MCDP2800-
> 903a5c8eddf6bffc-b4c059ea0025935c.jpeg
> 
> https://www.heise.de/newsticker/meldung/Intel-Celeron-Gemini-Lake-mit-HDMI-2-
> 0-und-SGX-3801532.html
> 
Geminilake is different from Apollolake, even though they belong to same GEN
family, GLK has a native HDMI 2.0 controller, whereas APL takes help from
LSPCON for HDMI 2.0 conversion.

> I have a second TV of the same model and it's connected to my main HTPC with
> an i3-6100 & GA-B150N Phoenix-WIFI board. This combination works quite fine,
> also the logging of those messages started with kernel 4.15 so I guess it's
> related to recent patches.
> 
> So all in all I'm pretty sure it's using the same lspcon & I didn't use the
> wrong system to gather information.

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