# Development log

## legolas: NVMe (Corsair MP600 ELITE / Phison E21) suspend/resume crashes

The drive hung on resume from S3 (deep) suspend — boot logs ended at `PM: suspend entry (deep)` with no resume, followed by a hard reboot. The Phison E21 can't recover from the D3 transition that S3 forces.

Investigation also found two existing workarounds were doing nothing:

- The udev rule `ATTR{d3cold_allowed}="0"` was a no-op — that sysfs attribute doesn't exist on this Phison endpoint or its parent root port (`0000:00:1d.0`).
- The `nvme-resume-fix` service was broken: `ExecStart` used `>` redirection without a shell, so `echo` just printed the string and never wrote to the `rescan` sysfs file. It never actually rescanned.

Changes (`hosts/legolas/hardware-configuration.nix`):

- Switched `mem_sleep_default` from `deep` (S3) to `s2idle` (modern standby). s2idle avoids the deep D3 path that hangs the drive.
- Removed the no-op `d3cold_allowed` rule and the broken rescan service.
- Added a correct runtime-PM-off udev rule on both the NVMe endpoint (`0000:6e:00.0`) and its parent root port (`0000:00:1d.0`), keeping the PCIe wakeup disable.

Note: runtime PM was already off on the endpoint (`power/control=on`); that alone never fixed the crash because system suspend uses a separate code path. Verify after rebuild that the cmdline has `mem_sleep_default=s2idle` (the old running generation showed a stale duplicate `deep`).