Created attachment 121843 [details] kern.log Hardware Platform: KABY LAKE-U CPU : Intel(R) Core(TM) @ 2.60GHz MCP : KBL-U G0 2+2 QDF : QYQ8 Chipset PCH: SPT-LP C1 CRB : KABY LAKE U DDR3L RVP7 CRB FAB1 BIOS : KBLSE2R1.R00.X015.B01.1511271314 ME FW : 11.5.0.1008 Ksc (EC FW): 1.20 Linux distribution: Ubuntu 15.10 64 bits Kernel drm-intel-nightly 4.5.0-rc4_e459990 from http://cgit.freedesktop.org/drm-intel/ commit e4599905334de9349501a383afb8503a1dde5728 Author: Jani Nikula <jani.nikula@intel.com> Date: Thu Feb 18 19:13:56 2016 +0200 drm-intel-nightly: 2016y-02m-18d-17h-13m-22s UTC integration manifest drm: tag libdrm-2.4.66 9b77443 from http://cgit.freedesktop.org/mesa/drm/ mesa: edf774b from http://cgit.freedesktop.org/mesa/mesa/ cairo: tag 1.15.2 db8a7f1 from http://cgit.freedesktop.org/cairo waffle: master bb29b2a from https://github.com/waffle-gl/waffle xorg-server-macros: master d7acec2 from git://git.freedesktop.org/git/xorg/util/macros libva: tag libva-1.6.1 1f026de from http://cgit.freedesktop.org/libva/ vaapi-intel-driver: e41040f from http://cgit.freedesktop.org/vaapi/intel-driver Firmware DMC 1.26 from https://01.org/linuxgraphics/downloads/skylake-dmc-1.26 MST Hub: MSTDP124DP Steps: ------ 1. Connect hub to DUT and 2 monitors to the hub (all is Display Port) 2. Boot 3. Wait Actual result: ------------- 3. DUT needs several minutes to boot. External screens do not display anything. Expected result: ---------------- 3. DUT boots normally and display works on external screen Info: ----- DUT boots normally without the hub connected It is reproduced with only one screen connected to the hub
Jim, any advice on how to proceed on this issue?
(In reply to yann from comment #1) > Jim, any advice on how to proceed on this issue? I would stop testing with two external displays on MST for now; that will be problematic until we have the DP link training rework in place. From what I'm seeing in dmesg, there are no MST-specific errors visible. There is a ton of power management noise in there that I would be suspicious of. I don't have a Kaby Lake myself, nor have I read much about it in the B-Spec, but clock setup is an area that has bitten us before, as is power management. There is one other thing that I find odd. Feb 19 14:29:34 KBLU1 kernel: [ 1.350958] [drm:intel_dp_probe_oui] Sink OUI: 0080e1 Feb 19 14:29:34 KBLU1 kernel: [ 1.353319] [drm:intel_dp_probe_oui] Branch OUI: 0080e1 Feb 19 14:29:34 KBLU1 kernel: [ 1.355688] [drm:intel_dp_probe_mst] Sink is MST capable I've never seen the Sink OUI and Branch OUI the same before, and I find this particularly odd considering that a hub is being used. What kind of monitors are being used? I'd suggest, for initial testing with MST, making sure that any external displays being used are 1080p monitors so that we don't run up against configurations that won't be valid for the given link bandwidth. Just for my own edification, can you please attach copies of the i915_display_info and i915_dp_mst_info files from debugfs with a DUT->MST Hub-><single 1080p monitor> configuration for me to look at? Please be sure that the single monitor is plugged into port 1 on the MST hub (many of the hubs require this.) Additionally, ensure that the MST hub is powered. Some use an external power supply, but some others expect to be powered off of a USB port that is on the hub. Please also test this on a more recent kernel; there have been several MST fixes recently, some in the area of power management, that could be impacting things here.
Thanks Jim your prompt reply. Christophe, please re-test using v4.6-rc5 or later. Moreover, attached i915_display_info and i915_dp_mst_info files as advised by Jim
Six months later, it seems to be a good time to retest this configuration given the link training patches merged upstream. Christophe, can you and QA do this?
With fresh setup, I confirm DUT boots without problems. I reported a new bug internally.
So closed
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