psys_suspend: do graceful teardown instead of returning -EBUSY

[jibsta210]

Problem

The current psys_suspend() refuses system-wide s2idle suspend with -EBUSY whenever psys->ready is set. Once a camera client has used PSYS even once (psys->ready becomes 1 in psys_runtime_pm_resume()), the only way it gets cleared is via the runtime-PM idle path. In practice this means s2idle suspend permanently fails after the first camera use on every Panther Lake laptop.

Reproducer (Dell XPS 16 PB16250, Lenovo ThinkPad X9, Latitude 9440, etc.):

sudo timeout 4 cam -c 1 --capture=4 --file=/tmp/r.raw   # first camera use
sudo systemctl suspend                                   # fails

dmesg shows:

intel_ipu7_psys.psys: PM: dpm_run_callback(): psys_suspend [intel_ipu7_psys] returns -16
intel_ipu7_psys.psys: PM: failed to suspend: error -16
PM: suspend of devices aborted after X.X msecs
PM: Some devices failed to suspend, or early wake event detected

Fix

Tail-call psys_runtime_pm_suspend() from psys_suspend(). The runtime suspend path already performs the correct teardown sequence (close FW ABI, stop FW, power down subdomains, MMU cleanup). On resume, runtime PM re-initializes PSYS lazily on next access.

Important caveat

This patch must be paired with a companion patch to drivers/staging/media/ipu7/ipu7.c that reorders ipu7_pci_remove() so ipu7_bus_del_devices() runs before ipu7_mmu_cleanup(). Without that companion fix, the MMU cleanup triggered here will later cause a NULL pointer dereference in find_iova() when isys_remove() runs.

The staging companion patch will be posted to linux-media@vger.kernel.org. I'm happy to submit it under your maintainership too if that's preferred.

Verification

Tested on Dell XPS 16 (Panther Lake, IPU7 + Synaptics SVP7500 CVS + ov08x40):

• Before: systemctl suspend fails with -EBUSY after first camera use
• After (patches paired): PM: suspend entry (s2idle) → PM: suspend exit cleanly, ~5s cycle, camera survives, libcamera re-enumerates after resume.

Tested-by: Jake Steinman j@metarealtyinc.ca
Signed-off-by: Jake Steinman j@metarealtyinc.ca