Re: [PATCH v6 01/13] Documentation: admin-guide: media: add rockchip camera interface

["Heiko Stübner" <heiko@sntech.de>]

Hey Michael,

Am Mittwoch, 30. April 2025, 11:15:50 Mitteleuropäische Sommerzeit schrieb Michael Riesch via B4 Relay:
> From: Michael Riesch <michael.riesch@collabora.com>
> 
> Add a document that describes the different variants of the Rockchip
> Camera Interface (CIF), their hardware layout, as well as their
> representation in the media controller centric rkcif device driver,
> which is located under drivers/media/platform/rockchip/rkcif.
> 
> Signed-off-by: Michael Riesch <michael.riesch@collabora.com>

> diff --git a/Documentation/admin-guide/media/rkcif.rst b/Documentation/admin-guide/media/rkcif.rst
> new file mode 100644
> index 000000000000..f35f644a54a0
> --- /dev/null
> +++ b/Documentation/admin-guide/media/rkcif.rst
> @@ -0,0 +1,83 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +=========================================
> +Rockchip Camera Interface (CIF)
> +=========================================
> +
> +Introduction
> +============
> +
> +The Rockchip Camera Interface (CIF) is featured in many Rockchip SoCs in
> +different variants.
> +The different variants are combinations of common building blocks, such as
> +
> +* INTERFACE blocks of different types, namely
> +
> +  * the Digital Video Port (DVP, a parallel data interface)
> +  * the interface block for the MIPI CSI-2 receiver
> +
> +* CROP units
> +
> +* MIPI CSI-2 receiver (not available on all variants): This unit is referred
> +  to as MIPI CSI HOST in the Rockchip documentation.
> +  Technically, it is a separate hardware block, but it is strongly coupled to
> +  the CIF and therefore included here.
> +
> +* MUX units (not available on all variants) that pass the video data to an
> +  image signal processor (ISP)
> +
> +* SCALE units (not available on all variants)
> +
> +* DMA engines that transfer video data into system memory using a
> +  double-buffering mechanism called ping-pong mode
> +
> +* Support for four streams per INTERFACE block (not available on all
> +  variants), e.g., for MIPI CSI-2 Virtual Channels (VCs)
> +
> +This document describes the different variants of the CIF, their hardware
> +layout, as well as their representation in the media controller centric rkcif
> +device driver, which is located under drivers/media/platform/rockchip/rkcif.
> +
> +Variants
> +========
> +
> +Rockchip PX30 Video Input Processor (VIP)
> +-----------------------------------------
> +
> +The PX30 Video Input Processor (VIP) features a digital video port that accepts
> +parallel video data or BT.656.
> +Since these protocols do not feature multiple streams, the VIP has one DMA
> +engine that transfers the input video data into system memory.
> +
> +The rkcif driver represents this hardware variant by exposing one V4L2 subdevice
> +(the DVP INTERFACE/CROP block) and one V4L2 device (the DVP DMA engine).
> +
> +Rockchip RK3568 Video Capture (VICAP)
> +-------------------------------------
> +
> +The RK3568 Video Capture (VICAP) unit features a digital video port and a MIPI
> +CSI-2 receiver that can receive video data independently.
> +The DVP accepts parallel video data, BT.656 and BT.1120.
> +Since the BT.1120 protocol may feature more than one stream, the RK3568 VICAP
> +DVP features four DMA engines that can capture different streams.
> +Similarly, the RK3568 VICAP MIPI CSI-2 receiver features four DMA engines to
> +handle different Virtual Channels (VCs).
> +
> +The rkcif driver represents this hardware variant by exposing up to three V4L2
> +subdevices:
> +
> +* rkcif-dvp0: INTERFACE/CROP block for the DVP
> +* rockchip-mipi-csi fdfb0000.csi: MIPI CSI-2 receiver
> +* rkcif-mipi0: INTERFACE/CROP block for the MIPI CSI-2 receiver
> +
> +and up to five V4L2 devices:
> +
> +* rkcif-dvp0-id0: The support for multiple streams on the DVP is not yet
> +  implemented, as it is hard to find test hardware. Thus, this video device
> +  represents the first DMA engine of the RK3568 DVP.
> +* rkcif-mipi0-id[0...3]: The four DMA engines of the RK3568 MIPI CSI-2
> +  receiver. Each DMA engine can capture a certain MIPI CSI-2 Virtual Channel.
> +
> +.. kernel-figure:: rkcif-rk3568-vicap.dot
> +    :alt:   Topology of the RK3568 Video Capture (VICAP) unit
> +    :align: center

in patch 6 you already have a block stating

	Finally, the RK3588 VICAP unit constitutes an essential piece of the
	camera interface with one DVP, six MIPI CSI-2 receivers, scale/crop
	units, and a data path multiplexer (to scaler units, to ISP, ...).

so the rk3588 seems to be on the table "soonish" ;-) .
So maybe also already include it here in the description already, if there
is a next version, and your investigation is already that far along?

Otherwise a really nice (and concise) read, and made me understand the
setup somewhat nicely.

Reviewed-by: Heiko Stuebner <heiko@sntech.de>