[PATCH v2 0/3] media: Enable the OV5693 front camera on IPU6 Surface devices

[Fernando Rimoli <fernandorimoli11@gmail.com>]

Apologies for the slow turnaround on v2, I wanted to properly
characterise the MIPI_CTRL00 register before answering, and I was
coordinating with Arsalan Naeem, who originally found the register write
(linux-surface PR#2171); the third patch is co-developed with him.

This enables the OV5693 front camera on Intel IPU6 Surface devices such as
the Microsoft Surface Pro 9. Three independent pieces are needed on a stock
kernel:

  1/3  ov5693: add the "OVTI5693" ACPI HID so the i2c core binds the driver
       (these devices enumerate the sensor as OVTI5693, not INT33BE).
  2/3  ipu-bridge: add the same HID so the bridge builds the sensor's fwnode
       graph.
  3/3  ov5693: gate the MIPI clock lane, which the IPU6 CSI-2 receiver needs
       in order to lock (this is the register write from PR#2171).

On the MIPI_CTRL00 value, in reply to Sakari's question on v1:

I swept the register on a Surface Pro 9 (IPU6) with read-back. The power-on
default reads 0x00. Every value with bit 5 (clock-lane gate) set streams
(300/300 frames, steady ~28 fps); every value with bit 5 clear, including
0x00 and 0x04 (LP11-idle alone), fails with "stream stop time out" and no
frames. So bit 5 is the decisive bit for IPU6, and 0x04 alone is not enough.
Bit 5 is not an IPU6-specific hack: ov5640, ov5647 and ov5648 all gate the
clock lane on every platform. Patch 3 sets bit 5 plus bit 2 (LP11-idle,
i.e. 0x24, matching ov5640's value); I have only been able to test this on
IPU6, not on IPU3 (CIO2) or Rockchip, so I have kept it to the conventional
OV-family bits rather than the vendor's 0x2d (which also sets bit 3 and an
undocumented bit 0).

Patches 1-2 are independent of patch 3 and useful on their own for
enumeration; patch 1 carries Dan Scally's Reviewed-by from v1.

Changes since v1 [1]:
- Split the single v1 patch into the two HID patches (1/3, 2/3), as
  requested by Sakari.
- Added patch 3/3, the MIPI clock-lane gate, co-developed with Arsalan
  Naeem, with the characterisation above answering Sakari's v1 question.
- Carried Daniel Scally's Reviewed-by on patch 1/3.
- Used named bit macros instead of a bare register value.

[1] https://lore.kernel.org/linux-media/20260708213633.18392-1-fernandorimoli11@gmail.com/

Fernando Rimoli (3):
  media: i2c: ov5693: Add OVTI5693 ACPI HID
  media: ipu-bridge: Add OVTI5693 to the list of supported sensors
  media: i2c: ov5693: Gate the MIPI clock lane for IPU6

 drivers/media/i2c/ov5693.c           | 21 +++++++++++++++++++++
 drivers/media/pci/intel/ipu-bridge.c |  2 ++
 2 files changed, 23 insertions(+)

-- 
2.43.0