I'm writing you to get more info about a possible bug we are experiencing on 
kernel 4.9 (details below). If this is not the proper address please accept my 
apologies and let me know where I should address my request to.
We are running Linux on a EMX-SKLUP machine 
This machine mounts a graphics card: Intel® Skylake U SoC integrated Graphics 
and we are using the i915 driver to drive two screens, one using the HDMI port 
and the other using the DisplayPort.
We tried different kernels and we noticed the following:

1.       Kernel 4.4 --> all versions work like a charm

2.       Kernel 4.9 --> all versions before 4.9.30 work. All versions after 
4.9.40 have problem with the HDMI port. It simply turns out to be always 
disconnected when issuing an xrandr. Thus, the screen is simply blank. The 
DisplayPort connection works perfectly.

We made some narrowing and the problem seems to have been introduced between 
the following two commits:
·         4.9.30 commit: 
·         4.9.40 commit: 
·         diff of i915 dir: 

3.       All following kernels  have the same problem.

I attach some info to the present email and I am at your disposal for any 
additional info you may need.
I thank you for any insight you can provide us to solve this issue.
Thanks a lot,

Enrico Deotto
Firmware and Software Manager
GDS / Global Display Solutions Spa
Via Tezze, 20/A - 36073 Cornedo (VI)

M: +39 3920961186
E.  e.deo...@gds.com<mailto:e.deo...@gds.com>

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