nvidia-sleep-hook
based on: https://download.nvidia.com/XFree86/Linux-x86_64/435.17/README/powermanagement.html
          https://www.linuxquestions.org/questions/slackware-14/how-to-get-wayland-working-on-a-nvidia-pascal-video-card-4175765650/
NOTE for the fix with nvidia-dbus.conf / nvidia-powerd:
That is a separate feature (Dynamic Boost: CPU<->GPU power budget
shifting on supported laptops) and plays no role in suspend or
resume; sleep works without it, as verified during testing. It is
therefore intentionally not shipped here. If you want Dynamic
Boost, set it up independently per the NVIDIA driver README.
=================

An elogind system-sleep hook that makes suspend and hibernate work
properly with the NVIDIA proprietary driver on Slackware.

Without it, systems running the NVIDIA driver commonly fail to
suspend, wake up instantly, or resume with corrupted graphics,
because the driver's default (kernel callback) power management
path can only preserve a small amount of video memory.

The hook drives the /proc/driver/nvidia/suspend interface at the
right moments of the sleep cycle, telling the driver to save all
video memory allocations to disk before sleeping and to restore
them on resume. This is the same mechanism the NVIDIA-provided
systemd units use, adapted to elogind.

The hook is a silent no-op on systems without the NVIDIA driver
(nouveau, legacy drivers without the /proc interface, or no NVIDIA
hardware at all), so it is safe to install anywhere.


Requirements
------------

* Slackware 15.0 or -current with elogind.
* NVIDIA proprietary driver new enough to provide
  /proc/driver/nvidia/suspend (470 series and later).
* The following kernel module options MUST be set. This package
  ships them in /etc/modprobe.d/nvidia-pm.conf (installed as .new,
  never clobbering an existing copy):

      options nvidia NVreg_PreserveVideoMemoryAllocations=1 NVreg_TemporaryFilePath=/var/tmp

  If you already set these options in your own modprobe file
  (e.g. /etc/modprobe.d/nvidia.conf), keep only one copy.

  Notes on NVreg_TemporaryFilePath:

  - It must point to a filesystem that is NOT tmpfs and supports
    unnamed temporary files (O_TMPFILE); any normal ext4/xfs/btrfs
    location is fine. /var/tmp is a good default on Slackware.
  - /var/tmp may be a separate mount on some systems; always check
    the actual filesystem behind it with: df -h /var/tmp
  - It must have at least as much free space as the video memory
    allocated at suspend time. Check your card's capacity with:
        nvidia-smi -q -d MEMORY | grep -A2 'FB Memory'
  - You will never see the temporary files in a directory listing;
    they are unnamed and exist only for the duration of the sleep
    cycle.

  A reboot (or full module unload/reload) is required for the
  options to take effect. Verify with:

      grep PreserveVideoMemoryAllocations /proc/driver/nvidia/params

  which must report: PreserveVideoMemoryAllocations: 1


Installation
------------

Via the SlackBuild, or manually:

    install -m 0755 nvidia-sleep.sh /etc/elogind/system-sleep/nvidia-sleep.sh

Then configure the module options as described above and reboot.


Usage
-----

Nothing to do: elogind runs every executable in
/etc/elogind/system-sleep/ automatically around each sleep cycle.
Suspend as usual (lid close, loginctl suspend, desktop menu).

Hybrid sleep and suspend-then-hibernate are handled with a
hibernate-grade video memory image, since both may end up resuming
from disk.

X11 note: when a running Xorg server is detected, the hook
switches to a spare virtual terminal before sleeping and back
afterwards, as required by the NVIDIA X driver. Wayland sessions
need no VT dance and none is performed.
Not tested in XLibre.


Troubleshooting
---------------

The hook logs every action via syslog with the tag "nvidia-sleep":

    grep nvidia-sleep /var/log/messages

* "suspend: FAILED (driver refused, see dmesg)" -- the driver
  could not save its state. Check dmesg; the usual causes are
  missing NVreg_PreserveVideoMemoryAllocations=1 (check
  /proc/driver/nvidia/params) or insufficient free space at
  NVreg_TemporaryFilePath.

* System still wakes up instantly even though the hook logs
  "suspend: ok" -- the problem is not the NVIDIA driver state but
  a spurious wakeup source (typically PCIe PME from the GPU root
  port, or a USB controller). Inspect dmesg after the failed
  cycle and /proc/acpi/wakeup, and disable the offending wakeup
  source.

* No log lines at all -- the hook exited early because
  /proc/driver/nvidia/suspend does not exist or is not writable;
  the NVIDIA driver is not loaded or is too old.


Author
------

Ioannis Anagnostakis (rizitis)