Changes between Version 8 and Version 9 of gscreboot

Timestamp:

06/01/2020 11:50:57 PM (4 years ago)

Author:

Cale Collins

Comment:

added systemd reset hack

gscreboot

@@ -125 +125 @@
 
 See the complete GSC reference [wiki:gsc here]
+
+= How to Override the Systemd Reboot Process on a Ventana
+
+Gateworks Ventana devices do not reboot using the same mechanisms as a traditional desktop computer. Attempting to reboot the device using traditional Linux commands will cause the device to hang and requires a power cycle to regain connectivity with the device. Rather, you must run a script that issues I2C commands to reset the device.
+We can work around this issue by changing the mechanism systemd uses to reboot the device to use the Ventana reboot script. This allows users and third-party configuration tools, such as Ansible, to reboot the system using traditional system utilities, such as **reboot** and **shutdown** without causing the device to hang.
+
+**
+NOTICE: The approach outlined in this section is admittedly a hack. It would likely be frowned upon by the authors of systemd. Further, an update or upgrade of systemd could revert the changes. Use at your own risk.
+**
+
+== Background
+Shutdown and reboot are managed by systemd on modern Ubuntu Linux installations. As a matter of fact, the **shutdown** and **reboot** utilities are simply symbolic links to the **systemctl** utility. When the **systemctl** utility is run as one of these commands, it instructs systemd to transition the system to the desired target. This is the reboot.target in the case of a reboot.
+The process systemd uses to reboot is documented in the [https://www.man7.org/linux/man-pages/man7/bootup.7.html bootup manpage], which can be viewed by running the command "man 7 bootup". This documentation shows that systemd transitions through a number of targets when it reboots shutting down services along the way. It runs the systemd-reboot.service as the last step to transition to the reboot.target. On Ubuntu 18.04, the content of systemd-reboot.service unit file is:
+
+{{{
+# SPDX-License-Identifier: LGPL-2.1+
+# This file is part of systemd.
+# systemd is free software; you can redistribute it and/or modify it
+# under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation; either version 2.1 of the License, or
+# (at your option) any later version.
+
+[Unit]
+Description=Reboot
+Documentation=man:systemd-halt.service(8)
+DefaultDependencies=no
+Requires=shutdown.target umount.target final.target
+After=shutdown.target umount.target final.target
+
+[Service]
+Type=oneshot
+ExecStart=/bin/systemctl --force reboot
+}}}
+
+Changing the systemd-reboot.service command line to run the Gateworks Ventana reboot script rather than run systemctl allows us to override the default
+reboot behavior.
+
+== Steps
+
+1. Copy the Gateworks Ventana reboot script to an appropriate location on the target operating system. Make sure it is owned by root and is marked as executable. In our case, we wrote the contents to /usr/bin/ventana_reboot.
+
+{{{
+#!/bin/sh
+#
+# usage: gsc_sleep [seconds]
+#
+# default 2 second sleep ensures between 1 and 2 seconds pass before powerup
+SECS=${1:-2}
+# syncs the filesystem
+echo "Syncing filesystems"
+sync
+# perform i2c transactions in loop to retry on i2c timeouts
+echo "Powering down for $SECS seconds"
+while [ 1 ]; do
+# set R6-R9 with 32bit number of seconds to wake
+i2cset -f -y 0 0x20 6 $((SECS % 256)) || continue
+SECS=$((SECS >> 8))
+i2cset -f -y 0 0x20 7 $((SECS % 256)) || continue
+SECS=$((SECS >> 8))
+i2cset -f -y 0 0x20 8 $((SECS % 256)) || continue
+SECS=$((SECS >> 8))
+i2cset -f -y 0 0x20 9 $((SECS % 256)) || continue
+# latch sleep time - taking care to not disturb other bits
+R1=$(i2cget -f -y 0 0x20 1) || continue
+R1=$((R1 | 0x04)) # set R1.2 LATCH_SLEEP
+i2cset -f -y 0 0x20 1 $R1 || continue
+# set R1.0 SLEEP_ENABLE and R1.1 ACTIVATE_SLEEP - taking care not to disturb other bits
+R1=$(i2cget -f -y 0 0x20 1) || continue
+R1=$((R1 | 0x03)) # set R1.0 and R1.1
+i2cset -f -y 0 0x20 1 $R1 || continue
+done
+}}}
+
+{{{#!bash
+chmod 777 /usr/bin/ventana_reboot
+}}}
+
+
+2. Edit /lib/systemd/system/systemd-reboot.service and replace the contents of the ExecStart entry with a call to the Gateworks Ventana reboot script.
+
+{{{
+# SPDX-License-Identifier: LGPL-2.1+
+# This file is part of systemd.
+# systemd is free software; you can redistribute it and/or modify it
+# under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation; either version 2.1 of the License, or
+# (at your option) any later version.
+
+[Unit]
+Description=Reboot
+Documentation=man:systemd-halt.service(8)
+DefaultDependencies=no
+Requires=shutdown.target umount.target final.target
+After=shutdown.target umount.target final.target
+
+[Service]
+Type=oneshot
+ExecStart=/usr/bin/ventana_reboot
+}}}
+
+3.  Reload systemd so that it picks up the changes.
+
+{{{#!bash
+systemctl daemon-reload
+}}}