[Bug 96659] New: dp to VGA dongle works intermittently

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=96659

            Bug ID: 96659
           Summary: dp to VGA dongle works intermittently
           Product: xorg
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Driver/intel
          Assignee: chris at chris-wilson.co.uk
          Reporter: michal at physics.ubc.ca
        QA Contact: intel-gfx-bugs at lists.freedesktop.org

I'm trying to get a reliable mini-dp to VGA connection for a dell XPS 13 (9343,
Broadwell) to a projector in a lecture theatre. I have a couple of dongles -
one Apple mini dp-VGA and one cheap mini dp to VGA/HDMI/DVI combo.

Either works if I just connect to a monitor over a short cable.

In the lecture theatre, the Apple dongle doesn't work at all, and the cheap
combo adapter works sometimes, perhaps 1 in 3 times I plug it in.

In windows the Apple dongle works fine.

I have tried setting drm_kms_helper.dp_aux_i2c_transfer_size to 1 and 4 (which
solved some problems with the apple adapter on ealier kernels) but this doesn't
seem to make a difference now.

I'm running Arch linux, with kernel 4.6.0, xorg-server-1.18.3-2,
xf86-video-intel-1:2.99.917+662+gb617f80-1

Setting drm.debug=14, The Apple dongle shows me:

[ 3134.274766] [drm:intel_get_hpd_pins] hotplug event received, stat
0x00200000, dig 0x10101012, pins 0x00000020
[ 3134.274775] [drm:intel_hpd_irq_handler] digital hpd port B - long
[ 3134.274779] [drm:intel_hpd_irq_storm_detect] Received HPD interrupt on PIN 5
- cnt: 0
[ 3134.274801] [drm:intel_dp_hpd_pulse] got hpd irq on port B - long
[ 3134.275271] [drm:intel_dp_get_dpcd] DPCD: 11 0a 82 01 00 03 01 81 00 00 00
00 00 00 00
[ 3134.275278] [drm:intel_dp_get_dpcd] Display Port TPS3 support: source yes,
sink no
[ 3134.275285] [drm:intel_dp_print_rates] source rates: 162000, 270000, 540000
[ 3134.275289] [drm:intel_dp_print_rates] sink rates: 162000, 270000
[ 3134.275293] [drm:intel_dp_print_rates] common rates: 162000, 270000
[ 3134.276100] [drm:intel_dp_probe_oui] Sink OUI: 000000
[ 3134.276453] [drm:intel_dp_probe_oui] Branch OUI: 0010fa
[ 3134.276467] [drm:i915_hotplug_work_func] running encoder hotplug functions
[ 3134.276472] [drm:i915_hotplug_work_func] Connector DP-1 (pin 5) received
hotplug event.
[ 3134.276476] [drm:intel_dp_detect] [CONNECTOR:45:DP-1]
[ 3134.277469] [drm:intel_dp_get_dpcd] DPCD: 11 0a 82 01 00 03 01 81 00 00 00
00 00 00 00
[ 3134.277475] [drm:intel_dp_get_dpcd] Display Port TPS3 support: source yes,
sink no
[ 3134.277482] [drm:intel_dp_print_rates] source rates: 162000, 270000, 540000
[ 3134.277488] [drm:intel_dp_print_rates] sink rates: 162000, 270000
[ 3134.277493] [drm:intel_dp_print_rates] common rates: 162000, 270000
[ 3134.278394] [drm:drm_dp_i2c_do_msg] native defer
[ 3134.279464] [drm:drm_dp_i2c_do_msg] native defer
[ 3134.280620] [drm:drm_dp_i2c_do_msg] I2C nack (result=0, size=0
[ 3134.281072] [drm:drm_dp_i2c_do_msg] native defer
[ 3134.282332] [drm:drm_dp_i2c_do_msg] native defer
[ 3134.283424] [drm:drm_dp_i2c_do_msg] native defer
[ 3134.284222] [drm:drm_dp_i2c_do_msg] I2C nack (result=0, size=0
[ 3134.284665] [drm:drm_dp_i2c_do_msg] native defer
[ 3134.285917] [drm:drm_dp_i2c_do_msg] native defer
[ 3134.286997] [drm:drm_dp_i2c_do_msg] native defer
[ 3134.287774] [drm:drm_dp_i2c_do_msg] I2C nack (result=0, size=0
[ 3134.288208] [drm:drm_dp_i2c_do_msg] native defer
[ 3134.289412] [drm:drm_dp_i2c_do_msg] native defer
[ 3134.290480] [drm:drm_dp_i2c_do_msg] native defer
[ 3134.291255] [drm:drm_dp_i2c_do_msg] I2C nack (result=0, size=0
[ 3134.291687] [drm:drm_dp_i2c_do_msg] native defer
[ 3134.292891] [drm:drm_dp_i2c_do_msg] native defer
[ 3134.293960] [drm:drm_dp_i2c_do_msg] native defer
[ 3134.294733] [drm:drm_dp_i2c_do_msg] I2C nack (result=0, size=0
[ 3134.295165] [drm:drm_dp_i2c_do_msg] native defer
[ 3134.295946] [drm:intel_dp_detect_dpcd] Broken DP branch device, ignoring
[ 3134.295949] [drm:i915_hotplug_work_func] Connector HDMI-A-1 (pin 5) received
hotplug event.
[ 3134.295951] [drm:intel_hdmi_detect] [CONNECTOR:49:HDMI-A-1]
[ 3134.296187] [drm:do_gmbus_xfer] GMBUS [i915 gmbus dpb] NAK for addr: 0050
w(1)
[ 3134.296189] [drm:do_gmbus_xfer] GMBUS [i915 gmbus dpb] NAK on first message,
retry
[ 3134.296391] [drm:do_gmbus_xfer] GMBUS [i915 gmbus dpb] NAK for addr: 0050
w(1)
[ 3134.296393] [drm:drm_do_probe_ddc_edid] drm: skipping non-existent adapter
i915 gmbus dpb
[ 3134.480116] [drm:intel_get_hpd_pins] hotplug event received, stat
0x00200000, dig 0x10101011, pins 0x00000020
[ 3134.480120] [drm:intel_hpd_irq_handler] digital hpd port B - short
[ 3134.480141] [drm:intel_dp_hpd_pulse] got hpd irq on port B - short
[ 3136.805463] [drm:drm_mode_addfb2] [FB:55]

I can provide dmesg traces for other situations if that's at all helpful.

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