A true mainline Linux Kernel for the Pinebook Pro
#85
(12-02-2019, 09:37 PM)tsys Wrote:
(12-02-2019, 11:20 AM)danielt Wrote: I tested today with all three of my USB-C to HDMI adapters... all can put up a display (and are reversible).

Thanks for testing! Kind of expected my cable to be at fault here.


Did also some tests with the standard-issue LMP mini-dock at my work place.
(I've put all the details in the USB-C docks thread in the Hardware subforum)

Long story short:
  • In my case, too. It only works in one orientation and never in the other (except USB-PD).
  • It's one of these which is supposed to be able to both USB-3 and HDMI 4k @60Hz (so able to dynamically assign high-speed lanes to either USB-3 or DisplayPort depending on needs).
  • It cycles weirdly
  • But if setup on a 2-lanes only mode (e.g.: 1920x1080 @24fps) everything works perfectly.

This strongly makes me think of some race condition happening between the OS trying to enumerate everything available (USB-PD, everything on USB-3, all the display modes on DP) and the drivers assigning high-speed lanes to either USB-3 or HDMI.

In one orientation: probing 4K @60Hz requires 4 DisplayPort lanes, which would yank out the two USB3 lanes, which would trigger a rescan of the USB-3, which in turn yaks out two out of the four DisplayPort lanes, etc. thus the on/off cycles.

In the other orientation: the probing reaches a dead end on the USB-3 lanes where nothing gets detected (random imaginary speculative example: the laptop looks for two USB-3 lanes on the high-speed lanes where the mini-dock gives Display lanes and vice versa). Only USB-PD works because it uses completely different lanes (the charging lanes and the detection lanes).

I might be completely wrong and it might be that the detection of alt-mode is just b0rked on that mini-dock. (the mini-dock just outputs wrong values on the auto-detect lanes, à la Raspberry Pi 4 pretending to be an unpowered audio-jack adapter due to wrong resistors pattern). But I thought it's worth sharing.

(12-06-2019, 06:57 AM)tsys Wrote: took me some time but I finally got around to enable CONFIG_COMPAT in the defconfig.

Cool, this will enable me to get Netflix running (requires Widevine on a 32-bits Google Chrome/Chromium), e.g.: in a 32bits chroot.

(12-06-2019, 06:57 AM)tsys Wrote: I've enabled CONFIG_KEXEC_FILE, too just in case someone wants to toy around with that.

...faster reboots into newer kernels?~ :-D


Messages In This Thread
RE: A true mainline Linux Kernel for the Pinebook Pro - by DrYak - 12-06-2019, 08:50 AM
5.12 - by kalpazanius - 04-26-2021, 04:38 PM
RE: 5.12 - by ramsey - 06-19-2021, 05:36 PM
RE: 5.12 - by linuxad - 06-20-2021, 09:26 AM

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