Re: [PATCH v7 2/6] media: admin-guide: Add starfive_camss.rst for Starfive Camera Subsystem

Jack Zhu
2023-07-31T03:39:49Z

Hi Laurent,

Thank you for your comments.

On 2023/7/27 18:23, Laurent Pinchart wrote:
> On Wed, Jul 26, 2023 at 12:26:18PM +0100, Bryan O'Donoghue wrote:
>> On 19/06/2023 12:28, Jack Zhu wrote:
>> > Add starfive_camss.rst file that documents the Starfive Camera
>> > Subsystem driver which is used for handing image sensor data.
>> >
>> > Signed-off-by: Jack Zhu <jack.zhu@starfivetech.com>
>> > ---
>> > .../admin-guide/media/starfive_camss.rst | 57 +++++++++++++++++++
>> > .../media/starfive_camss_graph.dot | 16 ++++++
>> > .../admin-guide/media/v4l-drivers.rst | 1 +
>> > MAINTAINERS | 1 +
>> > 4 files changed, 75 insertions(+)
>> > create mode 100644 Documentation/admin-guide/media/starfive_camss.rst
>> > create mode 100644 Documentation/admin-guide/media/starfive_camss_graph.dot
>> >
>> > diff --git a/Documentation/admin-guide/media/starfive_camss.rst b/Documentation/admin-guide/media/starfive_camss.rst
>> > new file mode 100644
>> > index 000000000000..a6378849384f
>> > --- /dev/null
>> > +++ b/Documentation/admin-guide/media/starfive_camss.rst
>> > @@ -0,0 +1,57 @@
>> > +.. SPDX-License-Identifier: GPL-2.0
>> > +
>> > +.. include:: <isonum.txt>
>> > +
>> > +================================
>> > +Starfive Camera Subsystem driver
>> > +================================
>> > +
>> > +Introduction
>> > +------------
>> > +
>> > +This file documents the driver for the Starfive Camera Subsystem found on
>> > +Starfive JH7110 SoC. The driver is located under drivers/media/platform/
>> > +starfive.
>> > +
>> > +The driver implements V4L2, Media controller and v4l2_subdev interfaces.
>> > +Camera sensor using V4L2 subdev interface in the kernel is supported.
>> > +
>> > +The driver has been successfully used on the Gstreamer 1.18.5 with
>> > +v4l2src plugin.
>> > +
>> > +
>> > +Starfive Camera Subsystem hardware
>> > +----------------------------------
>> > +
>> > +The Starfive Camera Subsystem hardware consists of:
>> > +
>> > +- MIPI DPHY Receiver: receives mipi data from a MIPI camera sensor.
>>
>> Feels like a terribe nit-pick but you have "mipi" and "MIPI" here. I'd
>> be consistent with one - recommend MIPI throughout your documentation.
>
> I'd drop the "mipi" and just write "data", not "MIPI data".
>

Ok, I will modify it.

>> > +- MIPI CSIRx Controller: is responsible for handling and decoding CSI2 protocol
>
> It's "CSI-2", not "CSI2".

Ok, I will modify it.

>
>> > + based camera sensor data stream.
>> > +- ISP: handles the image data streams from the MIPI CSIRx Controller.
>>
>> Maybe you've done this elsewhere but, it would be worthwhile describing
>> what the ISP does. Debayering ? 3As ? Just raw dumps ?
>>
>> > +- VIN(Video In): a top-level module, is responsible for controlling power
>> > + and clocks to other modules, dumps the input data to memory or transfers the
>> > + input data to ISP.
>
> A block diagram could be nice. Let me give it a try, based on my
> understanding:
>
> Starfive Camera Subsystem hardware
> ----------------------------------
>
> The Starfive Camera Subsystem hardware consists of::
>
> +---------------------------------------------+
> | VIN |
> +--------+ | +-------+ +-------+ +-----+ |
> | Camera |----->| D-PHY |-->| CSI-2 |-+->| DMA | |
> | Sensor | | | RX | | RX | | +-----+ |
> +--------+ | +-------+ +-------+ | |
> | | +-----+ +-----+ |
> | \->| ISP |-->| DMA | |
> | +-----+ +-----+ |
> +---------------------------------------------+
>
> - VIN (Video IN): The top-level module, responsible for controlling
> power and clocks, and routing data between modules.
>
> - D-PHY RX: The MIPI D-PHY receiver, receiving data from a MIPI CSI-2
> camera sensor.
>
> - CSI-2 RX: The MIPI CSI-2 receiver controller, responsible for decoding
> the CSI-2 protocol.
>
> - ISP: The ISP, processing raw Bayer data from the CSI-2 receiver and
> producing YUV frames.
>
>
> I haven't tried compiling this, so please fix formatting if anything is
> wrong (and of course feel free to adapt the diagram and text).
>

Ok, I will add a block diagram.

>> > +
>> > +
>> > +Topology
>> > +--------
>> > +
>> > +The media controller pipeline graph is as follows:
>> > +
>> > +.. _starfive_camss_graph:
>> > +
>> > +.. kernel-figure:: starfive_camss_graph.dot
>> > + :alt: starfive_camss_graph.dot
>> > + :align: center
>> > +
>> > +The driver has 2 video devices:
>> > +
>> > +- stf_vin0_wr_video0: capture device for images directly from the VIN module.
>>
>> OK so you can get the raw images.
>>
>> > +- stf_vin0_isp0_video1: capture device for images without scaling.
>> > +
>> > +The driver has 3 subdevices:
>> > +
>> > +- stf_isp0: is responsible for all the isp operations.
>> > +- stf_vin0_wr: used to dump RAW images to memory.
>> > +- stf_vin0_isp0: used to capture images for the stf_vin0_isp0_video1 device.
>>
>> But what is being output here ? RGB, jpeg, YUV ?
>> It would be worth adding a few bits of text to describe that so you
>> don't have to dive into code to understand it.
>

--
Regards,

Jack Zhu