IPU6 Meteor Lake: CSE authentication fails with error 0xc20 on Dell Latitude 7450 (OV02E10 sensor)

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### Summary
The IPU6 driver successfully detects the OmniVision OV02E10 camera sensor but fails to initialize due to CSE (Converged Security Engine) firmware authentication failure with error code `0xc20`. The sensor is completely inaccessible despite all drivers, firmware, and hardware being properly detected.

### Hardware Configuration
- **System:** Dell Latitude 7450
- **CPU:** Intel Meteor Lake
- **IPU6:** PCI device `0000:00:05.0` (Multimedia controller: Intel Corporation Meteor Lake IPU rev 04)
- **Camera Sensor:** OmniVision OV02E10
- ACPI device: `OVTI02E1:00`
- ACPI HID: `OVTI02E1`
- ACPI path: `\_SB_.PC00.LNK1`
- ACPI status: `0x15` (present, enabled, functioning)
- **BIOS:** Dell version 1.16.0 (2025-08-04) - Latest available
- **Secure Boot:** Disabled

### Software Configuration
- **OS:** Ubuntu 25.10 (Plucky Puffin)
- **Kernel:** 6.17.0-6-generic
- **Driver Package:** `intel-ipu6-dkms 0~git202506270118.9bff7368`
- **Sensor Module:** `ov02e10` (loaded, signed, author: Jingjing Xiong )
- **Firmware Files Tested:**
- `/lib/firmware/intel/ipu/ipu6epmtl_fw.bin` (signed, 456K, dated 2024-10-12)
- `/lib/firmware/intel/ipu/unsigned/ipu6epmtl_fw.bin` (unsigned, 456K, dated 2024-10-11)
- **MEI/CSE Status:** Working correctly
- Device: `/dev/mei0` active
- Firmware versions: `0:18.0.18.2571`, `0:18.0.18.2571`, `0:18.0.5.2077`
- `mei_gsc_proxy` active and bound to i915
- Modules loaded: `mei_gsc_proxy`, `mei_me`, `mei_vsc`, `mei`, `mei_vsc_hw`

### Error Details

Complete boot sequence showing the failure:

This error is **100% reproducible** and occurs at every boot and every manual module reload attempt.

### What Works ✅
- Sensor hardware detection via ACPI
- IPU6 PCI device enumeration and enablement
- Sensor driver (`ov02e10`) loads successfully
- Driver correctly identifies sensor: "Found supported sensor OVTI02E1:00"
- Driver reports: "Connected 1 cameras"
- MEI/GSC communication functional
- **BOOT_LOAD command to CSE completes successfully**

### What Fails ❌
- **CSE AUTHENTICATE_RUN returns `0xc20` instead of expected `0x2`**
- IPU6 driver probe fails with error -5 (EIO)
- No V4L2 subdevices created (`/dev/v4l-subdev*` remains empty)
- Sensor completely inaccessible to userspace
- libcamera IPU6 pipeline unavailable (sensor not enumerated)

### Configuration Files Present
libcamera has proper configuration for this sensor:
- `/usr/share/libcamera/ipa/ipu6/ov02e10.aiqb` (4.9K, JSON tuning data)
- `/usr/share/libcamera/ipa/simple/ov02e10.yaml` (sensor configuration)

### Attempted Solutions (All Failed)
1. ✗ Used unsigned firmware from `/lib/firmware/intel/ipu/unsigned/`
2. ✗ Rebuilt DKMS modules with `--force` flag
3. ✗ Disabled Secure Boot in BIOS
4. ✗ Updated to latest available BIOS version (1.16.0, August 2025)
5. ✗ Updated all `intel-ipu6-*` and `linux-firmware` packages
6. ✗ Tested multiple firmware versions (signed and unsigned)
7. ✗ Verified MEI/CSE is functioning (multiple firmware versions loaded)

### Technical Analysis

The CSE error code `0xc20` appears to indicate a configuration/compatibility authentication rejection. The sequence shows:

1. **BOOT_LOAD succeeds** ✅ - CSE can communicate with IPU6
2. **AUTHENTICATE_RUN fails with 0xc20** ❌ - CSE rejects firmware signature/authentication

This suggests one of the following:
1. Missing or incorrect signing key in CSE for this specific hardware revision
2. Firmware incompatibility with Meteor Lake IPU6 rev 04 on Dell OEM systems
3. Dell-specific CSE configuration that doesn't recognize Intel's firmware signatures
4. CSE provisioning issue specific to this Dell Latitude model

### Questions for Intel

1. **Is there a Dell Latitude 7450-specific firmware version** that needs to be signed with different keys?
2. **Does the CSE on Meteor Lake require additional provisioning** or OEM-specific keys for IPU6 firmware?
3. **Is this a known issue with certain OEM implementations** of Meteor Lake (specifically Dell)?
4. **What does CSE error code 0xc20 specifically mean** in the context of IPU6 firmware authentication?
5. **Are there MEI/CSE debug tools** that could provide more detailed information about why authentication fails?
6. **Is there a firmware update roadmap** for addressing CSE authentication issues on OEM systems?

### Impact

This bug makes the internal camera **completely unusable** on Dell Latitude 7450 systems with Meteor Lake, despite:
- All hardware being properly detected
- All drivers being installed and signed
- Latest BIOS and firmware updates applied
- Proper ACPI configuration

### Additional Information Available

I can provide upon request:
- Complete dmesg logs
- Full ACPI tables dump
- Detailed MEI/CSE status output
- lspci -vvv output
- Any other debugging information needed

### Workaround

Currently using an external USB webcam as the internal camera is non-functional.

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**System Information Summary:**
- Dell Latitude 7450, BIOS 1.16.0
- Meteor Lake IPU6 rev 04 (PCI 0000:00:05.0)
- OmniVision OV02E10 sensor (ACPI: OVTI02E1:00)
- Ubuntu 25.10, Kernel 6.17.0-6-generic
- intel-ipu6-dkms 0~git202506270118.9bff7368
- CSE firmware: 18.0.18.2571 / 18.0.5.2077