Kernel Driver Organization

Device Tree

• The OV5640 camera connection to the Qualcomm ISP is described by the kernel file 'arch/arm64/boot/dts/qcom/d3-camera-mezzanine.dtsi'.
• The camera subsystem driver, alias camss, is listed in the beginning with two physical ports.
  • Each port defined must be attached to a valid sensor in order for the subsystem to complete the bind operation.
  • The board is only shipped with one sensor, so the second port is disabled in the released code tree.
• The camera sensors, ov5640, are assigned in the second section assigned to BLSP 6.
  • The first sensor on J3 is physically using the Camera Control Interface port or CCI.
    • The CCI driver in development by Linaro does not act as a full I2C driver for this release.
    • The ov5640 driver includes a hack along with a flag in the device tree to indicate that the CCI port should be used instead of BLSP6.
    • The device tree boolean flag 'qcom,use_cci' should be set for the J3 port to indicate the CCI connection.
  • The port also includes two flags for default horizontal and vertical flip settings: 'ovti,vflip' and 'ovti,hflip'.
    • By default the vertical flip is set. This is the correct orientation for a vertically oriented board with the sensor on top and folded over.
    • The sensor orientations can be changed by modifying these flags.
    • Instructions to modify the flags can be found here: Sensor Flip Flags

OV5640 Driver

• The OV5640 driver can be found in the kernel file ['drivers/media/i2c/ov5640.c'] (https://github.com/D3Engineering/linux_kernel_qcomlt/blob/d3/release/ov5640_4.9.27/drivers/media/i2c/ov5640.c).
  • This driver contains modifications specific to the current MSM camera subsystem.
  • The driver supports 1080p@30 fps resolution and outputs UYVY 422 8-bit.
  • The following V4L2 subdevice controls are supported
    • V4L2_CID_SATURATION
    • V4L2_CID_AUTO_WHITE_BALANCE
    • V4L2_CID_AUTOGAIN
    • V4L2_CID_EXPOSURE_AUTO
    • V4L2_CID_TEST_PATTERN
    • V4L2_CID_HFLIP
    • V4L2_CID_VFLIP

QCom Camera Subsystem

• The camera subsystem driver code is located in the kernel folder 'drivers/media/platform/qcom'.
• The MSM camera driver subsystem is under development by Linaro.
• It is composed of the following components:
  • CCI - camera control interface, an I2C port for sensor communication.
  • CSIPHY->CSID->ISPIF - dual ISP interfaces for MIPI CSI2 camera capture.
  • VFE - Three configurable outputs from the ISP for different resolutions and color formats. Entities vfe0_rdi0 and vfe0_rdi1 support UYVY 422 on /dev/video0 and dev/video1 respectively; vfe0_pix supports NV12M 420 on /dev/video3.