[Lunar Lake] Protocol Error (-71) and I2C Speed Bottleneck on OV08X40 via Synaptics SVP7500 Bridge

[tjchan001]

Hardware Environment

• System: Dell Lunar Lake (Core Ultra Series 2 / Ultra 7 268V)
• Bridge: Synaptics SVP7500 (USB-to-I2C/MIPI Bridge)
• Sensor: OmniVision OV08X40 (ID: OVTI08F4:00)
• Driver: intel_ipu7 (Staging) / i2c_usbio / ivsc-csi

Issue Description

Attempts to stream from the OV08X40 sensor result in a Protocol error (-71) at STREAMON. Following the error, the Synaptics USB bridge appears to reset or latch-up, causing the device nodes to disappear (No such device) until a full cold boot is performed.

New Findings: IVSC & Firmware Gaps

Investigation with Secure Boot disabled confirms that the Intel Vision Sensing Controller (IVSC) stack is present but non-functional due to missing sensor-specific firmware.

1. Missing Firmware Blobs: /lib/firmware/intel/vsc/ contains firmware for other sensors but lacks ivsc_pkg_ovti08x40_0.bin and ivsc_skucfg_ovti08x40_0_1.bin.
2. IVSC Idle State: While ivsc-csi and ivsc-ace modules load, they fail to bind to the sensor, leaving it to bind directly to intel_ipu7_isys. This bypasses the secure handshake/authentication required by the hardware.

Observed Critical Failures

1. I2C Clock Speed Cap (The "Smoking Gun")

The usbio-i2c bridge driver forces a downclock from 400kHz to 100kHz. This latency appears to prevent the sensor from being configured within the IPU7's MIPI timing window.

[17.229199] i2c_usbio.usbio-i2c usbio.usbio-i2c.0: Invalid speed 400000 adjusting to bus max 100000

2. MIPI Link Timeout / Protocol Error

Even with manual resolution alignment (3856x2176), the CSI-2 receiver times out:

[17.779903] intel_ipu7_isys.isys intel_ipu7.isys.40: bind ov08x40 17-0036 nlanes is 2 port is 0
[20681.798345] intel_ipu7_isys.isys intel_ipu7.isys.40: enable streams Intel IPU7 CSI2 0 failed with -71

3. Entity Mismatch (Resolution Padding)

The sensor defaults to 3856x2176, while the ISYS pipeline defaults to a 12MP or 1080p target, leading to initial Broken pipe errors before manual alignment via media-ctl.

4. Firmware/GPIO Bug

The driver fails to map the physical reset line via the USB bridge:
Plaintext

[17.123913] gpio_usbio.usbio-gpio usbio.usbio-gpio.0: [Firmware Bug]: GPIO 4 is not in FW pins bitmap

Steps to Reproduce

(Optional) Disable Secure Boot and manually modprobe ivsc-csi.

Align pipeline to sensor native output: media-ctl -d /dev/media0 -V '"Intel IPU7 CSI2 0":0 [fmt:SGRBG10_1X10/3856x2176]'

Attempt capture: v4l2-ctl -d /dev/video0 --stream-mmap --stream-count=1 --stream-to=test.raw

Result: VIDIOC_STREAMON returned -1 (Protocol error).

Analysis

The combination of a 100kHz I2C bottleneck on the Synaptics bridge and missing IVSC sensor firmware creates a fatal race condition. The sensor cannot transition to High-Speed MIPI mode fast enough to satisfy the IPU7's watchdog timer. Furthermore, the direct binding of the sensor to ISYS (bypassing the IVSC) likely leaves the MIPI physical lanes in a low-power or locked state.

[tjchan001]

Update: Captured Synaptics Bridge Hardware Crash (-108) I have successfully built and injected a patched ov08x40 driver with added fsleep(100ms) delays to mitigate I2C latency. However, during the STREAMON sequence, the Synaptics SVP7500 bridge physically disconnects from the USB bus.

Critical Log Snippet:

[ 297.943136] usbio-bridge 3-3:1.0: Bulk in error -108
[ 297.943153] ov08x40 i2c-OVTI08F4:00: Failed to write reg 0x5152. error = -71
[ 297.943161] ov08x40 i2c-OVTI08F4:00: ov08x40_start_streaming failed to set plls
[ 298.924027] usb 3-3: new full-speed USB device number 5 using xhci_hcd
[ 299.048872] usb 3-3: Product: SVP7500

Observation: The bridge appears to encounter a watchdog reset or a power-state transition failure when the IPU7 attempts to enable streams. The -108 error indicates the link is physically severed. Manual attempts to set formats via media-ctl return Invalid argument (22) immediately after this reset event.