Context

• See hibernate-pocket, hibernate-pocket-2 hibernate-pocket-3 hibernate-pocket-4

A Kernel Patch

• The follow patch looks potentially relevant:

https://patchwork.kernel.org/project/linux-rockchip/patch/20250509-b4-pci_dwc_reset_support-v3-1-37e96b4692e7@wdc.com/

• git clone https://github.com/torvalds/linux.git (Is there a better place? kernel.org is pretty opaque)

• are the pre-reqs in mnt kernel? The patch header contains

    base-commit: 08733088b566b58283f0f12fb73f5db6a9a9de30
    change-id: 20250430-b4-pci_dwc_reset_support-d720dbafb7ea
    prerequisite-change-id: 20250404-pcie-reset-slot-730bfa71a202:v4
    prerequisite-patch-id: 2dad85eb26838d89569b12c19d70f392fa592667
    prerequisite-patch-id: 6238a682bd8e9476e5911b7a59263c3fc618d63e
    prerequisite-patch-id: 37cab00bc255a62b1e8396a48a3afba5e1751abd
    prerequisite-patch-id: ff711f65cf9926374646b76cd38bdd823d576764
    prerequisite-patch-id: 1654cca919d024b9a9190b28e90f722975c797e8

• First check and see what is upstream. I had to remember how to use git-patch-id and also how to split a long regex disjunction into multiple lines.

git log --patch --no-merges v6.13.. | \
  git patch-id --stable | \
  grep -F -e 2dad85eb26838d89569b12c19d70f392fa592667 \
    -e 6238a682bd8e9476e5911b7a59263c3fc618d63e \
    -e 37cab00bc255a62b1e8396a48a3afba5e1751abd \
    -e ff711f65cf9926374646b76cd38bdd823d576764 \
    -e 1654cca919d024b9a9190b28e90f722975c797e8

yields

37cab00bc255a62b1e8396a48a3afba5e1751abd d1c696dba120624256ab335ab8247f535b872309
2dad85eb26838d89569b12c19d70f392fa592667 b06d125e6280603a34d9064cd9c12748ca2edb04

The two commits that are actually found, are only in tag 'v6.16~rc1'

• The discussion on LKML mentions pci/slot-reset. Where does that branch live?

git remote add pci https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git
git fetch pci
git for-each-ref refs/remotes/pci --format "%(refname)" | \
    while read branch
    do
        echo "checking $branch"
        git log --patch --no-merges --since 2025-01-01 $branch | \
            git patch-id --stable | \
            grep -F -e 2dad85eb26838d89569b12c19d70f392fa592667 \
                 -e 6238a682bd8e9476e5911b7a59263c3fc618d63e \
                 -e 37cab00bc255a62b1e8396a48a3afba5e1751abd \
                 -e ff711f65cf9926374646b76cd38bdd823d576764 \
                 -e 1654cca919d024b9a9190b28e90f722975c797e8
    done

This did not find any more commits, but I did learn how to use git-for-each-ref, so I guess not a total loss.

previous episode

Context

• See hibernate-pocket, hibernate-pocket-2 hibernate-pocket-3

Log from (failed) platform test

After some fun I got the serial console working and re-ran the platform test.

After a bit of reading the serial console, I realized that rmmod dwc3 was causing more problems than it solved, in particularly reliable hard lockup on one of the CPUs.

My revised test script is

set -x
echo platform >  /sys/power/pm_test
echo reboot > /sys/power/disk
sleep 2
rmmod mt76x2u
sleep 2
echo disk >  /sys/power/state
sleep 2
modprobe mt76x2u

The current problem seems to be pcie not resuming properly.

[   65.306842] usbcore: deregistering interface driver mt76x2u
[   65.343606] wlx000a5205eb2d: deauthenticating from 20:05:b7:00:2d:89 by local choice (Reason: 3=DEAUTH_LEAVING)
[   67.995239] PM: hibernation: hibernation entry
[   68.048103] Filesystems sync: 0.022 seconds
[   68.049005] Freezing user space processes
[   68.051075] Freezing user space processes completed (elapsed 0.001 seconds)
[   68.051760] OOM killer disabled.
[   68.052597] PM: hibernation: Basic memory bitmaps created
[   68.053108] PM: hibernation: Preallocating image memory
[   69.719040] PM: hibernation: Allocated 366708 pages for snapshot
[   69.719650] PM: hibernation: Allocated 1466832 kbytes in 1.66 seconds (883.63 MB/s)
[   69.720370] Freezing remaining freezable tasks
[   69.723558] Freezing remaining freezable tasks completed (elapsed 0.002 seconds)
[   69.728002] rk_gmac-dwmac fe1b0000.ethernet end0: Link is Down
[   69.992324] rockchip-dw-pcie a40c00000.pcie: Failed to receive PME_TO_Ack
[   69.993405] PM: hibernation: debug: Waiting for 5 seconds.
[   76.059484] rockchip-dw-pcie a40c00000.pcie: Phy link never came up
[   76.060043] rockchip-dw-pcie a40c00000.pcie: fail to resume
[   76.060546] rockchip-dw-pcie a40c00000.pcie: PM: dpm_run_callback(): genpd_restore_noirq returns -110
[   76.061363] rockchip-dw-pcie a40c00000.pcie: PM: failed to restore noirq: error -110

previous episode|next episode

Context

• See hibernate-pocket, hibernate-pocket-2

Serial console hardware

• Manual is unclear about name of connector (J16 in schematics, J17 in manual).
• Also numbering of pins is not given afaict.
• Clone https://source.mnt.re/reform/pocket-reform.git
• Look at pocket-reform-motherboard.kicad_pcb
• From the PCB I can confirm J16 and pins numbered left (sysctl) to right.
• attach "dtech" prolific PL2303 based serial to usb cable per serial console section of PR manual
• lsusb shows ID 067b:23a3 Prolific Technology, Inc. ATEN Serial Bridge
• install tio
• add my user to group dialout
• newgrp dialout
• tio /dev/ttyUSB0 -b 1500000
• A closer look at the PCB in kicad makes me realize the pin labels in the manual are wrong. 4 = GND, 5 = UART1_RX, 6= UART1_TX. With that change I have U-boot output on boot.

Serial console software

With some help from minute on ircs://irc.libera.chat:6697/#mnt-reform, I got the kernel boot arguments right to have not just u-boot output but linux kernel output on the serial console. In consfigurator notation

(on-change
      (file:has-content "/etc/flash-kernel/ubootenv.d/00reform2_serial_console"
        "setenv bootargs \"${bootargs} console=ttyS2,1500000 keep_bootcon\"")
    (cmd:single "flash-kernel"))

The filename should sort before "00reform2_ubootenv" so that the existing "console=tty1" still ends up at the end.

previous episode|next episode

Context

• See hibernate-pocket

Testing continued

• following a suggestion of gordon1, unload the mediatek module first. The following seems to work, either from the console or under sway

echo devices >  /sys/power/pm_test
echo reboot > /sys/power/disk
rmmod mt76x2u
echo disk >  /sys/power/state
modprobe mt76x2u

• It even works via ssh (on wired ethernet) if you are a bit more patient for it to come back.
• replacing "reboot" with "shutdown" doesn't seem to affect test mode.
• replacing "devices" with "platform" (or "processors") leads to unhappiness.
  • under sway, the screen goes blank, and it does not resume
  • same on console

previous episode|next episode

Configuration

• script: https://docs.kernel.org/power/basic-pm-debugging.html

• kernel is 6.15.4-1~exp1+reform20250628T170930Z

State of things

• normal reboot works

• Either from the console, or from sway, the intial test of reboot mode hibernate fails. In both cases it looks very similar to halting.

  • the screen is dark (but not completely black)
  • the keyboard is still illuminated
  • the system-controller still seems to work, althought I need to power off before I can power on again, and any "hibernation state" seems lost.

Running tests

• this is 1a from above
• freezer test passes
• devices test from console
  • console comes back (including input)
  • networking (both wired and wifi) seems wedged.
  • console is full of messages from mt76x2u about vendor request 06 and 07 failing. This seems related to https://github.com/morrownr/7612u/issues/17
  • at some point the console becomes non-responsive, except for the aforementioned messages from the wifi module.
• devices test under sway
  • display comes back
  • keyboard/mouse seem disconnected
  • network down / disconnected?

next episode

Because of course the system that UNB paid literal millions of dollars for cannot actually tell me if students in my course have passed (with C or above) the single prerequisite course. I could handle either a small number of false positives, but apparently it also has an unknown number of false negatives (missed students) and no way to detect those without checking every student. Which makes this very expensive report useless.

In the unlikely event someone else finds this useful. Or just wants to make fun of my Python.

import csv
import sys

enrolled=set()
passed=set()
record={}

with open (sys.argv[1], 'r') as rosterfile:
    rosterreader=csv.DictReader(rosterfile)
    for row in rosterreader:
        id=row['Student ID']
        enrolled.add(id)
        record[id]=row

with open ('report.csv', 'w') as outfile:        
    with open (sys.argv[2], 'r') as historyfile:
        historyreader=csv.DictReader(historyfile)
        writer = None
        for row in historyreader:
            if not writer:
                fields=row.keys()
                writer = csv.DictWriter(outfile,fieldnames=fields)
                writer.writeheader()
                
            id=row['StudentID']
            grade=row['Final Grade']
            if not grade in ['F', 'D', 'C-']:
                passed.add(id)
                
            if id in enrolled:
                writer.writerow(row)

print("Students missing prerequisite:\n")
for id in enrolled.difference(passed):
    row=record[id]
    print(f"{row['Student ID']}\t{row['Student Name']}\t{row['Preferred Email']}")

My web pages are (still) in ikiwiki, but lately I have started authoring things like assignments and lectures in org-mode so that I can have some literate programming facilities. There is is org-mode export built-in, but it just exports source blocks as examples (i.e. unhighlighted verbatim). I added a custom exporter to mark up source blocks in a way ikiwiki can understand. Luckily this is not too hard the second time.

(with-eval-after-load "ox-md"
  (org-export-define-derived-backend 'ik 'md
    :translate-alist '((src-block . ik-src-block))
    :menu-entry '(?m 1 ((?i "ikiwiki" ik-export-to-ikiwiki)))))

(defun ik-normalize-language  (str)
  (cond
   ((string-equal str "plait") "racket")
   ((string-equal str "smol") "racket")
   (t str)))

(defun ik-src-block (src-block contents info)
  "Transcode a SRC-BLOCK element from Org to beamer
         CONTENTS is nil.  INFO is a plist used as a communication
         channel."
  (let* ((body  (org-element-property :value src-block))
         (lang  (ik-normalize-language (org-element-property :language src-block))))
    (format "[[!format <span class="error">Error: unsupported page format &#37;s</span>]]" lang body)))

(defun ik-export-to-ikiwiki
    (&optional async subtreep visible-only body-only ext-plist)
  "Export current buffer as an ikiwiki markdown file.
    See org-md-export-to-markdown for full docs"
  (require 'ox)
  (interactive)
  (let ((file (org-export-output-file-name ".mdwn" subtreep)))
    (org-export-to-file 'ik file
      async subtreep visible-only body-only ext-plist)))

See web-stacker for the background.

yantar92 on #org-mode pointed out that a derived backend would be a cleaner solution. I had initially thought it was too complicated, but I have to agree the example in the org-mode documentation does pretty much what I need.

This new approach has the big advantage that the generation of URLs happens at export time, so it's not possible for the displayed program code and the version encoded in the URL to get out of sync.

;; derived backend to customize src block handling
(defun my-beamer-src-block (src-block contents info)
  "Transcode a SRC-BLOCK element from Org to beamer
         CONTENTS is nil.  INFO is a plist used as a communication
         channel."
  (let ((attr (org-export-read-attribute :attr_latex src-block :stacker)))
    (concat
     (when (or (not attr) (string= attr "both"))
       (org-export-with-backend 'beamer src-block contents info))
     (when attr
       (let* ((body  (org-element-property :value src-block))
              (table '(? ?\n ?: ?/ ?? ?# ?[ ?] ?@ ?! ?$ ?& ??
                         ?( ?) ?* ?+ ?, ?= ?%))
              (slug (org-link-encode body table))
              (simplified (replace-regexp-in-string "[%]20" "+" slug nil 'literal)))
         (format "\n\\stackerlink{%s}" simplified))))))

(defun my-beamer-export-to-latex
    (&optional async subtreep visible-only body-only ext-plist)
  "Export current buffer as a (my)Beamer presentation (tex).
    See org-beamer-export-to-latex for full docs"
  (interactive)
  (let ((file (org-export-output-file-name ".tex" subtreep)))
    (org-export-to-file 'my-beamer file
      async subtreep visible-only body-only ext-plist)))

(defun my-beamer-export-to-pdf
    (&optional async subtreep visible-only body-only ext-plist)
  "Export current buffer as a (my)Beamer presentation (PDF).
  See org-beamer-export-to-pdf for full docs."
  (interactive)
  (let ((file (org-export-output-file-name ".tex" subtreep)))
    (org-export-to-file 'my-beamer file
      async subtreep visible-only body-only ext-plist
      #'org-latex-compile)))

(with-eval-after-load "ox-beamer"
  (org-export-define-derived-backend 'my-beamer 'beamer
    :translate-alist '((src-block . my-beamer-src-block))
    :menu-entry '(?l 1 ((?m "my beamer .tex" my-beamer-export-to-latex)
                        (?M "my beamer .pdf" my-beamer-export-to-pdf)))))

An example of using this in an org-document would as below. The first source code block generates only a link in the output while the last adds a generated link to the normal highlighted source code.

* Stuff
** Frame
#+attr_latex: :stacker t
#+NAME: last
#+BEGIN_SRC stacker :eval no
  (f)
#+END_SRC

#+name: smol-example
#+BEGIN_SRC stacker :noweb yes
  (defvar x 1)
  (deffun (f)
    (let ([y 2])
      (deffun (h)
        (+ x y))
      (h)))
  <<last>>
#+END_SRC

** Another Frame 
#+ATTR_LATEX: :stacker both
#+begin_src smol :noweb yes
  <<smol-example>>
#+end_src

The Emacs part is superceded by a cleaner approach

I the upcoming term I want to use KC Lu's web based stacker tool.

The key point is that it takes (small) programs encoded as part of the url.

Yesterday I spent some time integrating it into my existing org-beamer workflow.

In my init.el I have

(defun org-babel-execute:stacker (body params)
  (let* ((table '(? ?\n ?: ?/ ?? ?# ?[ ?] ?@ ?! ?$ ?& ??
                    ?( ?) ?* ?+ ?, ?= ?%))
         (slug (org-link-encode body table))
         (simplified (replace-regexp-in-string "[%]20" "+" slug nil 'literal)))
    (format "\\stackerlink{%s}" simplified)))

This means that when I "execute" the block below with C-c C-c, it updates the link, which is then embedded in the slides.

#+begin_src stacker :results value latex :exports both
  (deffun (f x)
    (let ([y 2])
      (+ x y)))
  (f 7)
#+end_src
#+RESULTS:
#+begin_export latex
\stackerlink{%28deffun+%28f+x%29%0A++%28let+%28%5By+2%5D%29%0A++++%28%2B+x+y%29%29%29%0A%28f+7%29}
#+end_export

The \stackerlink macro is probably fancier than needed. One could just use \href from hyperref.sty, but I wanted to match the appearence of other links in my documents (buttons in the margins).

This is based on a now lost answer from stackoverflow.com; I think it wasn't this one, but you get the main idea: use \hyper@normalise.

\makeatletter
% define \stacker@base appropriately
\DeclareRobustCommand*{\stackerlink}{\hyper@normalise\stackerlink@}
\def\stackerlink@#1{%
  \begin{tikzpicture}[overlay]%
    \coordinate (here) at (0,0);%
    \draw (current page.south west |- here)%
    node[xshift=2ex,yshift=3.5ex,fill=magenta,inner sep=1pt]%
    {\hyper@linkurl{\tiny\textcolor{white}{stacker}}{\stacker@base?program=#1}}; %
  \end{tikzpicture}}
\makeatother

Problem description(s)

For some of its cheaper dedicated servers, OVH does not provide a KVM (in the virtual console sense) interface. Sometimes when a virtual console is provided, it requires a horrible java applet that won't run on modern systems without a lot of song and dance. Although OVH provides a few web based ways of installing,

• I prefer to use the debian installer image I'm used to and trust, and
• I needed some way to debug a broken install.

I have only tested this in the OVH rescue environment, but the general approach should work anywhere the rescue environment can install and run QEMU.

QEMU to the rescue

Initially I was horrified by the ovh forums post but eventually I realized it not only gave a way to install from a custom ISO, but provided a way to debug quite a few (but not all, as I discovered) boot problems by using the rescue env (which is an in-memory Debian Buster, with an updated kernel). The original solution uses VNC but that seemed superfluous to me, so I modified the procedure to use a "serial" console.

Preliminaries

• Set up a default ssh key in the OVH web console
• (re)boot into rescue mode
• ssh into root@yourhost (you might need to ignore changing host keys)
• cd /tmp
• You will need qemu (and may as well use kvm). ovmf is needed for a UEFI bios.

    apt install qemu-kvm ovmf

• Download the netinstaller iso

• Download vmlinuz and initrd.gz that match your iso. In my case:

  https://deb.debian.org/debian/dists/testing/main/installer-amd64/current/images/cdrom/

Doing the install

• Boot the installer in qemu. Here the system has two hard drives visible as /dev/sda and /dev/sdb.

qemu-system-x86_64               \
   -enable-kvm                    \
   -nographic \
   -m 2048                         \
   -bios /usr/share/ovmf/OVMF.fd  \
   -drive index=0,media=disk,if=virtio,file=/dev/sda,format=raw  \
   -drive index=1,media=disk,if=virtio,file=/dev/sdb,format=raw  \
   -cdrom debian-bookworm-DI-alpha2-amd64-netinst.iso \
   -kernel ./vmlinuz \
   -initrd ./initrd.gz \
   -append console=ttyS0,9600,n8

• Optionally follow Debian wiki to configure root on software raid.
• Make sure your disk(s) have an ESP partition.
• qemu and d-i are both using Ctrl-a as a prefix, so you need to C-a C-a 1 (e.g.) to switch terminals
• make sure you install ssh server, and a user account

Before leaving the rescue environment

• You may have forgotten something important, no problem you can boot the disks you just installed in qemu (I leave the apt here for convenient copy pasta in future rescue environments).

apt install qemu-kvm ovmf && \
qemu-system-x86_64               \
   -enable-kvm                    \
   -nographic \
   -m 2048                         \
   -bios /usr/share/ovmf/OVMF.fd  \
   -drive index=0,media=disk,if=virtio,file=/dev/sda,format=raw  \
   -drive index=1,media=disk,if=virtio,file=/dev/sdb,format=raw  \
   -nic user,hostfwd=tcp:127.0.0.1:2222-:22 \
   -boot c

• One important gotcha is that the installer guess interface names based on the "hardware" it sees during the install. I wanted the network to work both in QEMU and in bare hardware boot, so I added a couple of link files. If you copy this, you most likely need to double check the PCI paths. You can get this information, e.g. from udevadm, but note you want to query in rescue env, not in QEMU, for the second case.

• /etc/systemd/network/50-qemu-default.link

[Match]
Path=pci-0000:00:03.0
Virtualization=kvm

[Link]
Name=lan0

• /etc/systemd/network/50-hardware-default.link

[Match]
Path=pci-0000:03:00.0
Virtualization=no

[Link]
Name=lan0

• Then edit /etc/network/interfaces to refer to lan0