[PATCH RFC 0/4] media: i2c: Add Samsung S5K3L6 and Librem 5 rear camera

[Vincent Cloutier]

From: Vincent Cloutier <vincent@xxxxxxxxxxx>

This RFC fixes the i.MX8MQ CSI-2 reset path needed by Librem 5 camera
capture, adds initial upstream support for the Samsung S5K3L6 image
sensor, and wires it up as the rear camera on the Purism Librem 5.

This is intentionally a rewrite, not a direct forwarding of the Librem 5
downstream S5K3L6 carry. The downstream history is a long bring-up
series with debugfs register overrides, debug-frame plumbing, commented-out
old subdev code, FIXME/TODO scaffolding, and several API-era migrations.
This RFC collapses the usable production path into a current V4L2 sensor
driver using CCI regmap, runtime PM, fwnode endpoint validation, and the
current subdev stream API.

Many thanks to Martin Kepplinger, Dorota Czaplejewicz, and Sebastian
Krzyszkowiak for the original Librem 5 S5K3L6 driver work and rear-camera
bring-up. Martin authored the initial downstream driver, and Dorota and
Sebastian substantially developed the mode tables, controls, power-up
sequence, and sensor tuning that this rewrite is based on.

This series covers:

- 25 MHz input clock, matching the Librem 5 downstream configuration
- two MIPI CSI-2 data lanes
- RAW8 and RAW10 SGRBG modes at 1052x780, 2104x1560, and 4208x3120
- exposure, analogue gain, digital gain, blanking, pixel-rate,
  link-frequency, test-pattern, orientation, and rotation controls
- Librem 5 DTS integration for the rear sensor and second CSI-2 path

The rewritten driver and DTS path have now been tested on Librem 5r4
hardware in a v7.1.1 carry build, with the i.MX8MQ CSI-2 reset fix from this
series applied.

Patch 1 keeps the i.MX8MQ CSI-2 software reset sequence compatible with
the Librem 5 camera pipeline by making the post-assert reset release
SoC-specific. This is included as an RFC prerequisite for the Librem 5
rear-camera enablement; if preferred, it can be split out and handled as
a separate media/platform fix.

Vincent Cloutier (4):
  media: imx8mq-mipi-csi2: Keep i.MX8MQ reset assert-only
  dt-bindings: media: i2c: Add Samsung S5K3L6 image sensor
  media: i2c: Add Samsung S5K3L6 image sensor driver
  arm64: dts: imx8mq-librem5: Add rear camera

 .../bindings/media/i2c/samsung,s5k3l6.yaml    | 117 ++
 arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi |  51 +
 drivers/media/i2c/Kconfig                         |  10 +
 drivers/media/i2c/Makefile                        |   1 +
 drivers/media/i2c/s5k3l6.c                         | 1055 +++++++++++++++++
 drivers/media/platform/nxp/imx8mq-mipi-csi2.c     |   9 +-
 6 files changed, 1241 insertions(+), 2 deletions(-)

-- 
2.53.0