Hi Todor, A few small comments below: On 08/08/2017 03:30 PM, Todor Tomov wrote: > Add a document to describe Qualcomm Camera Subsystem driver. > > Signed-off-by: Todor Tomov <todor.tomov@xxxxxxxxxx> > --- > Documentation/media/v4l-drivers/qcom_camss.rst | 124 +++++++++++++++++++++++++ > 1 file changed, 124 insertions(+) > create mode 100644 Documentation/media/v4l-drivers/qcom_camss.rst > > diff --git a/Documentation/media/v4l-drivers/qcom_camss.rst b/Documentation/media/v4l-drivers/qcom_camss.rst > new file mode 100644 > index 0000000..4707ea7 > --- /dev/null > +++ b/Documentation/media/v4l-drivers/qcom_camss.rst > @@ -0,0 +1,124 @@ > +.. include:: <isonum.txt> > + > +Qualcomm Camera Subsystem driver > +================================ > + > +Introduction > +------------ > + > +This file documents the Qualcomm Camera Subsystem driver located under > +drivers/media/platform/qcom/camss-8x16. > + > +The current version of the driver supports the Camera Subsystem found on > +Qualcomm MSM8916 and APQ8016 processors. > + > +The driver implements V4L2, Media controller and V4L2 subdev interfaces. > +Camera sensor using V4L2 subdev interface in the kernel is supported. > + > +The driver is implemented using as a reference the Qualcomm Camera Subsystem > +driver for Android as found in Code Aurora [#f1]_. > + > + > +Qualcomm Camera Subsystem hardware > +---------------------------------- > + > +The Camera Subsystem hardware found on 8x16 processors and supported by the > +driver consists of: > + > +- 2 CSIPHY modules. They handle the Physical layer of the CSI2 receivers. > + A separate camera sensor can be connected to each of the CSIPHY module; > +- 2 CSID (CSI Decoder) modules. They handle the Protocol and Application layer > + of the CSI2 receivers. A CSID can decode data stream from any of the CSIPHY. > + Each CSID also contains a TG (Test Generator) block which can generate > + artificial input data for test purposes; > +- ISPIF (ISP Interface) module. Handles the routing of the data streams from > + the CSIDs to the inputs of the VFE; > +- VFE (Video Front End) module. Contains a pipeline of image processing hardware > + blocks. The VFE has different input interfaces. The PIX input interface feeds > + the input data to the image processing pipeline. Three RDI input interfaces > + bypass the image processing pipeline. The VFE also contains the AXI bus > + interface which writes the output data to memory. Can you explain what PIX and RDI stand for? I would also think it is a good idea to add a comment at the top of the various subdev sources that say a bit more than just "CSID Module". A simple "CSID (CSI Decoder) Module" is enough. Just so the reader knows what it is all about. Otherwise I don't have any more comments about this series. I don't need a v5 for this, if you can just post one patch for this documentation and one patch improving the source comments as described above, then that's fine with me. Regards, Hans > + > + > +Supported functionality > +----------------------- > + > +The current version of the driver supports: > + > +- input from camera sensor via CSIPHY; > +- generation of test input data by the TG in CSID; > +- raw dump of the input data to memory. RDI interface of VFE is supported. > + PIX interface (ISP processing, statistics engines, resize/crop, format > + conversion) is not supported in the current version; > +- concurrent and independent usage of two data inputs - could be camera sensors > + and/or TG. > + > + > +Driver Architecture and Design > +------------------------------ > + > +The driver implements the V4L2 subdev interface. With the goal to model the > +hardware links between the modules and to expose a clean, logical and usable > +interface, the driver is split into V4L2 sub-devices as follows: > + > +- 2 CSIPHY sub-devices - each CSIPHY is represented by a single sub-device; > +- 2 CSID sub-devices - each CSID is represented by a single sub-device; > +- 2 ISPIF sub-devices - ISPIF is represented by a number of sub-devices equal > + to the number of CSID sub-devices; > +- 3 VFE sub-devices - VFE is represented by a number of sub-devices equal to > + the number of RDI input interfaces. > + > +The considerations to split the driver in this particular way are as follows: > + > +- representing CSIPHY and CSID modules by a separate sub-device for each module > + allows to model the hardware links between these modules; > +- representing VFE by a separate sub-devices for each RDI input interface allows > + to use the three RDI interfaces concurently and independently as this is > + supported by the hardware; > +- representing ISPIF by a number of sub-devices equal to the number of CSID > + sub-devices allows to create linear media controller pipelines when using two > + cameras simultaneously. This avoids branches in the pipelines which otherwise > + will require a) userspace and b) media framework (e.g. power on/off > + operations) to make assumptions about the data flow from a sink pad to a > + source pad on a single media entity. > + > +Each VFE sub-device is linked to a separate video device node. > + > +The complete list of the media entities (V4L2 sub-devices and video device > +nodes) is as follows: > + > +- msm_csiphy0 > +- msm_csiphy1 > +- msm_csid0 > +- msm_csid1 > +- msm_ispif0 > +- msm_ispif1 > +- msm_vfe0_rdi0 > +- msm_vfe0_video0 > +- msm_vfe0_rdi1 > +- msm_vfe0_video1 > +- msm_vfe0_rdi2 > +- msm_vfe0_video2 > + > + > +Implementation > +-------------- > + > +Runtime configuration of the hardware (updating settings while streaming) is > +not required to implement the currently supported functionality. The complete > +configuration on each hardware module is applied on STREAMON ioctl based on > +the current active media links, formats and controls set. > + > + > +Documentation > +------------- > + > +APQ8016 Specification: > +https://developer.qualcomm.com/download/sd410/snapdragon-410-processor-device-specification.pdf > +Referenced 2016-11-24. > + > + > +References > +---------- > + > +.. [#f1] https://source.codeaurora.org/quic/la/kernel/msm-3.10/ >
