Hi Hans, On 18.08.2017 10:45, Hans Verkuil wrote: > 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. Thank you for the review again. I'll post two additional patches to add explanations of the abbreviations. > > 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/ >> > -- Best regards, Todor Tomov
