i915 link training failed with NXP PTN3460 eDP to LVDS bridge
- System architecture: x86_64
- Kernel version: 5.10.145-intel-pk-standard (built from Yocto layer meta-intel, kirkstone branch)
- Linux distribution: Poky 4.0.6 (kirkstone)
- Machine or mother board model: custom industry board:
- CPU: Intel(R) Atom(TM) CPU E3826 @ 1.46GHz
- 00:00.0 Host bridge: Intel Corporation Atom Processor Z36xxx/Z37xxx Series SoC Transaction Register (rev 11)
- 00:02.0 VGA compatible controller: Intel Corporation Atom Processor Z36xxx/Z37xxx Series Graphics & Display (rev 11)
- Display connector: DP-1
- dmesg (drm.debug=0x1e log_buf_len=4M) is attached
- note kernel oops "i915 0000:00:02.0: timed out waiting for [ENCODER:75:DP B] port ready: got 0xf, expected 0x0"
- note "i915 0000:00:02.0: [drm:intel_dp_link_train_phy [i915]] [CONNECTOR:76:DP-1][ENCODER:75:DP B][DPRX] Link Training failed at link rate = 270000, lane count = 2"
- note "i915 0000:00:02.0: [drm:intel_dp_link_train_phy [i915]] [CONNECTOR:76:DP-1][ENCODER:75:DP B][DPRX] Link Training failed at link rate = 162000, lane count = 2"
- xrandr --verbose is attached
- note the message "xrandr: Output DP1 is not disconnected but has no modes"
Additional information:
- 1 out of 20 of our boards show this behaviour, the others can easily train their DP links and use mode 1366x768
- might be connected to Firmware of PTN3460 (which is unknown so far, unfortunately)
- other kernel versions slightly differ in behaviour, for instance 5.15 retries training the link continiously. Then a reset of the PTN3460 results in successful link training
- Kernel 4.4.1 is said to work fine, unfortunately not yet confirmed by me during my tests
Edited by Andreas Ufert