Created attachment 122917 [details]
dmesg log

OS：Fedora 22
kernel：4.6.0-rc3
CPU：E3-1225 v5
BIOS version:5.11
bug：In Xwindows，unplug and replug HDMI，the HDMI not display
kernel message has one error:[drm] failed to retrieve link info, disabling eDP

Can you give me the hardware configuration? I am trying on a NUC and a hp monitor.

xrandr --verbose for

1. monitor plugged in,
2. monitor unplugged,
3. monitor plugged back

to confirm that the HDMI's connection is not being reported correctly.

(In reply to anusha from comment #3)
> Can you give me the hardware configuration? I am trying on a NUC and a hp
> monitor.

(In reply to Chris Wilson from comment #4)
> xrandr --verbose for
> 
> 1. monitor plugged in,
> 2. monitor unplugged,
> 3. monitor plugged back
> 
> to confirm that the HDMI's connection is not being reported correctly.

(In reply to Chris Wilson from comment #4)
> xrandr --verbose for
> 
> 1. monitor plugged in,
> 2. monitor unplugged,
> 3. monitor plugged back
> 
> to confirm that the HDMI's connection is not being reported correctly.

I try it on text mode and modify drivers/gpu/drm/i915/intel_hotplug.c
                                 i915_hotplug_work_func{
                                      ......
                                      struct intel_encoder *intel_encoder;
                                      struct drm_connector *connector;
                                      bool changed = false;
                                      u32 hpd_event_bits;
                                      //add by me
                                      int i;
                                      for(i=0;i<1000;i++){
                                      udelay(1000);
                                      }//add end
                                      ......
                                 }

Then,the hotplug will be ok. But in Xwindows，unplug and replug HDMI，the HDMI also not display.So,I doubt that is  Xwindow problem.

(In reply to anusha from comment #3)
> Can you give me the hardware configuration? I am trying on a NUC and a hp
> monitor.

I try it on a Acer al2216w and a ViewSonic VA2010wb monitor.
CPU:E3-1225 v5
South Bridge：C236

Anusha - any news from your side? 
yuechao.zhao@advantech.com.cn - Are you still seeing this? Maybe you have details also from newer kernel on Fedora 23, 24 or 25.

Dear Jari Tahvanainen
Thank you so much
I already fixed this bug on my kernel. There seems to be a problem with the i915 driver. The driver will be enter power-save modes when unplug HDMI.But We can not wake up it when replug HDMI So,I remove this function.
Then, this bug will be closed

(In reply to yuechao.zhao from comment #8)
> Dear Jari Tahvanainen
> Thank you so much
> I already fixed this bug on my kernel. There seems to be a problem with the
> i915 driver. The driver will be enter power-save modes when unplug HDMI.But
> We can not wake up it when replug HDMI So,I remove this function.
> Then, this bug will be closed

If it's a bug in upstream kernel, having it fixed in your kernel is not good enough for us.

It looks like you didn't reply to Chris' requests. I think it's unclear if you have a userspace component responding to hotplug uevents too.

Dear Jani Nikula
Thank for your answer.
I'm sorry. I forget CHris' requests.
About Chris' requests.I try it about half a year before.The HDMI's connection being reported correctly when I unplug HDMI and replug HDMI on first time(drm and i915 debug mode to be opened).But when I unplug HDMI and replug HDMI on second time,it don't report any kernel message.The driver already enter power-save mode and cann't wake it up in any way.

Anyway, I only want to HDMI can hotpulg.So I remove "enter power-save" function.This change not affect the performance of my system.
But the HDMI's hotplug issue may be our hardware design issues or BIOS issues.I'm not going to try to pursue it any furthe because I have not enough time.

Thank for your help.