linux-kernel - [REGRESSION] HDMI connector detection broken in 6.3 on Intel(R) Celeron(R) N3060 integrated graphics

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Date:   Thu, 10 Aug 2023 22:33:00 +0300
From:   Mikhail Rudenko <mike.rudenko@...il.com>
To:     Thomas Zimmermann <tzimmermann@...e.de>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>
Cc:     <linux-kernel@...r.kernel.org>, <regressions@...ts.linux.dev>,
        <dri-devel@...ts.freedesktop.org>,
        <intel-gfx@...ts.freedesktop.org>
Subject: [REGRESSION] HDMI connector detection broken in 6.3 on Intel(R)
 Celeron(R) N3060 integrated graphics

The following is a copy an issue I posted to drm/i915 gitlab [1] two
months ago. I repost it to the mailing lists in hope that it will help
the right people pay attention to it.

After kernel upgrade from 6.2.13 to 6.3 HDMI connector detection is
broken for me. Issue is 100% reproducible:

1. Start system as usual with HDMI connected.
2. Disconnect HDMI
3. Connect HDMI back
4. Get "no signal" on display, connector status in sysfs is disconnected

Curiously, running xrandr over ssh like

    ssh qnap251.local env DISPLAY=:0 xrandr

makes display come back. drm-tip tip is affected as well (last test
2023-08-02).

Bisecting points at a4e771729a51 ("drm/probe_helper: sort out poll_running vs poll_enabled").
Reverting that commit on top of 6.3 fixes the issue for me.

System information:
* System architecture: x86_64
* Kernel version: 6.3.arch1
* Linux distribution: Arch Linux
* Machine: QNAP TS-251A, CPU: Intel(R) Celeron(R) CPU N3060 @ 1.60GHz
* Display connector: single HDMI display
* dmesg with debug information (captured on drm-tip, following above 4 steps): [2]
* xrandr output:

    Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 16384 x 16384
    DP-1 disconnected (normal left inverted right x axis y axis)
    HDMI-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 708mm x 398mm
       1920x1080     60.00*+  50.00    59.94    30.00    25.00    24.00    29.97    23.98
       1920x1080i    60.00    50.00    59.94
       1360x768      59.80
       1280x768      60.35
       1280x720      60.00    50.00    59.94
       1024x768      75.03    70.07    60.00
       832x624       74.55
       800x600       75.00    60.32
       720x576       50.00
       720x480       60.00    59.94
       640x480       75.00    60.00    59.94
       720x400       70.08
    DP-2 disconnected (normal left inverted right x axis y axis)
    HDMI-2 disconnected (normal left inverted right x axis y axis)```

I'm willing to provide additional information and/or test fixes.

[1] https://gitlab.freedesktop.org/drm/intel/-/issues/8451
[2] https://gitlab.freedesktop.org/drm/intel/uploads/fda7aff0b13ef20962856c2c7be51544/dmesg.txt

#regzbot introduced: a4e771729a51

--
Best regards,
Mikhail Rudenko