[REGRESSION] media: ipu-bridge: IVSC camera no longer probes since v7.2 (CVS fallback returns the IVSC platform device)

[Martin Jeanne <martin@badakan.com>]

Hi,

Since v7.2 the built-in camera of my Dell XPS 14 9440 (Meteor Lake, IPU6
[8086:7d19], ov02c10 sensor behind an IVSC, ACPI INTC10CF) is no longer
detected. v7.1.9 works, 7.2.3 (Arch Linux distro kernel) does not, on
every boot.

The only change to this path between v7.1 and v7.2 is

c6b1b34b5090 ("media: pci: intel: Add CVS support for IPU bridge driver")

Before it, ipu_bridge_get_ivsc_csi_dev() returned NULL when the IVSC
platform device existed but its MEI CSI child had not been enumerated yet,
so ipu_bridge_init() failed with -ENODEV and the IPU6 driver deferred probe
and retried later. v7.1.9 log:

intel_vsc intel_vsc: silicon stepping version is 0:2
pci 0000:00:05.0: deferred probe pending: intel-ipu6: IPU6 bridge init 
failed
pci 0000:00:05.0: Found supported sensor OVTI02C1:00
ov02c10 i2c-OVTI02C1:00: supply dovdd not found, using dummy regulator

With the commit, that case now falls through to the CVS fallback:

/* Fallback to platform bus for CVS device */
return bus_find_device_by_acpi_dev(&platform_bus_type, adev);

Here the IVSC ACPI device is itself on the platform bus
(/sys/bus/platform/devices/INTC10CF:00), so the fallback returns it, the
bridge takes it for the CSI device and succeeds immediately, and the
software nodes end up on the wrong device. When mei_csi probes ten seconds
later it has no fwnode and fails hard. 7.2.3 log:

intel-ipu6 0000:00:05.0: Found supported sensor OVTI02C1:00
intel-ipu6 0000:00:05.0: Connected 1 cameras
intel_vsc intel_vsc: silicon stepping version is 0:2
ivsc_csi intel_vsc-92335fcf-3203-4472-af93-7b4453ac29da: mei-csi probed 
without device fwnode!
mei intel_vsc-5db76cf6-0a68-4ed6-9b78-0361635e2447: deferred probe 
pending: (reason unknown)

No i2c-OVTI02C1:00 device is created and libcamera reports "No sensor found
for /dev/media0". The function is unchanged in linux-7.2.y and in master.

I think the CVS fallback should only be taken when no IVSC platform device
exists at all: when one is found but its MEI CSI child is missing, keep
returning NULL so the IPU driver defers as before.

Happy to test patches.

#regzbot introduced: c6b1b34b5090

Martin Jeanne