[BUG] i915 HDMI connector status is connected after disconnection

Chris Chiu chiu at endlessm.com
Tue Sep 11 10:25:37 UTC 2018

On Fri, Aug 24, 2018 at 11:04 PM, Jani Nikula <jani.nikula at intel.com> wrote:
> On Wed, 22 Aug 2018, Chris Chiu <chiu at endlessm.com> wrote:
>> On Fri, Jul 6, 2018 at 2:44 PM, Chris Chiu <chiu at endlessm.com> wrote:
>>> On Thu, Jul 5, 2018 at 10:40 PM, Ville Syrjälä
>>> <ville.syrjala at linux.intel.com> wrote:
>>>> On Thu, Jul 05, 2018 at 03:58:36PM +0800, Chris Chiu wrote:
>>>>> Hi,
>>>>>     We have few ASUS laptops X705FD (The new WiskyLake), X560UD (intel
>>>>> i5-8250U), X530UN (intel i7-8550U) share the same problem, which is
>>>>> the HDMI connector status stays connected even the HDMI cable has been
>>>>> unplugged. Look into the "/sys/class/drm/card0-HDMI-A-1/status" for
>>>>> checking the status while plug/unplug the HDMI, it shows
>>>>> "disconnected" before plug in HDMI cable, then switch to "connected"
>>>>> after plugin, and still stay "connected" after unplug. This would
>>>>> cause the audio output path cannot correctly switch from HDMI to
>>>>> internal speaker after unplugging the HDMI.
>>>>> I then try to verify with the latest kernel 4.18.0-rc3+, the bug still
>>>>> present. The full "dmesg" log is here.
>>>>> https://gist.github.com/mschiu77/d761d7c5cf191b7868d4d7788ae087f1
>>>>> The HDMI cable is plugged in at ~26th second.
>>>>> "[ 26.214371] [drm:drm_detect_monitor_audio [drm]] Monitor has basic
>>>>> audio support"
>>>>> then unplug the HDMI at ~73th second.
>>>>> "[ 73.328361] [drm:drm_detect_monitor_audio [drm]] Monitor has basic
>>>>> audio support"
>>>>> Please advise what I can do to fix this. Thanks
>>>> Pull the cable out faster?
>>>> I presume this is the same old case of hpd disconnecting slightly
>>>> before ddc and we still manage to read the EDID when processing
>>>> the hpd irq. We kinda tried to fix that with the live status
>>>> check but that thing failed spectacularly.
>>>> --
>>>> Ville Syrjälä
>>>> Intel
>> There's a patch https://bugs.freedesktop.org/show_bug.cgi?id=107125#c8.
>> And I verified on the X705FD/X560UD which were easy to reproduce, the patch
>> works as expected. Can anyone kindly give comments about this patch?
>> We can do anything to help fix this issue upstream. Thanks
> Seems like a hack. Should look into hw based debouncing or a slight
> delay in the hotplug work processing I think.
> BR,
> Jani.
So you're suggesting to add a slight delay directly in i915_hotplug_work_func()?
And any suggestion about the 'hw based' debouncing? Maybe some examples
that I can refer to?


>> Chris
>>> Thanks for the suggestion. I tried pulling the cable out faster, the status
>>> shows correctly. I also tried branch drm-tip of
>>> https://cgit.freedesktop.org/drm/drm-tip
>>> but the symptom persists.
>>> Anything I can help here? Or any old commit/patch I can try to do some
>>> experiments?
>>> Chris
> --
> Jani Nikula, Intel Open Source Graphics Center

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