[BUG] i915 HDMI connector status is connected after disconnection

[Chris Chiu]

On Tue, Sep 11, 2018 at 6:25 PM, Chris Chiu <chiu at endlessm.com> wrote:
> 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.
>>

I tried to add a slight delay in the hotplug work as follows

--- a/drivers/gpu/drm/i915/intel_hotplug.c
+++ b/drivers/gpu/drm/i915/intel_hotplug.c
@@ -378,6 +378,8 @@ static void do_i915_hotplug_check(struct work_struct *work,

        spin_unlock_irq(&dev_priv->irq_lock);

+       msleep(100);
+
        drm_connector_list_iter_begin(dev, &conn_iter);
        drm_for_each_connector_iter(connector, &conn_iter) {
                intel_connector = to_intel_connector(connector);

It does work in most cases, but still fail to update the status if I
unplug the HDMI
cable very slow. I basically pull the HDMI cable in loose connected
state first, and
hold in that state ~1 second, totally unplug after that. The status in
sysfs will report
connected as it used to. There was no problem when I tried the patch
https://bugs.freedesktop.org/show_bug.cgi?id=107125#c8

I'll try to modify this patch a little bit and send upstream for
discussion later. Please
advise if any. Thanks.

Chris

> 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?
>
> Thanks
>
>>>
>>> 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