Re: [PATCH 00/14] Allwinner MIPI CSI-2 support for A31/V3s/A83T

Helen Koike
2020-10-30T22:44:43Z

Hi Paul,

I have some comments through the series, I hope this helps.

On 10/23/20 2:45 PM, Paul Kocialkowski wrote:
> This series introduces support for MIPI CSI-2, with the A31 controller that is
> found on most SoCs (A31, V3s and probably V5) as well as the A83T-specific
> controller. While the former uses the same MIPI D-PHY that is already supported
> for DSI, the latter embeds its own D-PHY.
>
> In order to distinguish the use of the D-PHY between Rx mode (for MIPI CSI-2)
> and Tx mode (for MIPI DSI), a submode is introduced for D-PHY in the PHY API.
> This allows adding Rx support in the A31 D-PHY driver.
>
> A few changes and fixes are applied to the A31 CSI controller driver, in order
> to support the MIPI CSI-2 use-case.
>
> Follows is the V4L2 device topology representing the interactions between
> the MIPI CSI-2 sensor, the MIPI CSI-2 controller (which controls the D-PHY)
> and the CSI controller:
> - entity 1: sun6i-csi (1 pad, 1 link)
> type Node subtype V4L flags 0
> device node name /dev/video0
> pad0: Sink
> <- "sun6i-mipi-csi2":1 [ENABLED,IMMUTABLE]
>
> - entity 5: sun6i-mipi-csi2 (2 pads, 2 links)
> type V4L2 subdev subtype Unknown flags 0
> pad0: Sink
> <- "ov5648 0-0036":0 [ENABLED,IMMUTABLE]
> pad1: Source
> -> "sun6i-csi":0 [ENABLED,IMMUTABLE]
>
> - entity 8: ov5648 0-0036 (1 pad, 1 link)
> type V4L2 subdev subtype Sensor flags 0
> device node name /dev/v4l-subdev0

Question: I noticed is that sun6i-mipi-csi2 doesn't expose a node under /dev/, but the sensor
exposes it. Probably because it uses V4L2_SUBDEV_FL_HAS_DEVNODE and sun6i-csi() calls
v4l2_device_register_subdev_nodes().

I find this weird from a userspace pov, since usually we don't mix manual and auto propagation
of the configs, so I started wondering if sun6i-csi driver should be calling
v4l2_device_register_subdev_nodes() in the first place.

Also, sun6i-csi doesn't seem to be used by any board dts (it's declared on the dtsi, but I
didn't find any dts enabling it), so I wonder if it would be a bad thing if we update it.

> pad0: Source
> [fmt:SBGGR8_1X8/640x480@1/30 field:none colorspace:raw xfer:none ycbcr:601 quantization:full-range]
> -> "sun6i-mipi-csi2":0 [ENABLED,IMMUTABLE]

If I understand correctly, this is very similar to ipu3:
sensor->bus->dma_engine

in the case of ipu3-cio2:
sensor->ipu3-csi2->ipu3-cio2

in this case:
ov5648->sun6i-mipi-csi2->sun6i-csi

On thing that is confusing me is the name csi2 with csi (that makes me think of csi
vesun6i-csirsion one, which is not the case), I would rename it to sun6i-video (or maybe
it is just me who gets confused).
I know this driver is already upstream and not part of this series, but on the other hand it
doesn't seem to be used.

On another note, I always wonder if we should expose the bus in the topology, I'm not
sure if it provides any useful API or information for userspace, and you could have
a cleaner code (maybe code could be under phy subsystem). But at the same time, it
seems this is a pattern on v4l2.

I'd like to hear what others think on the above.

Regards,
Helen

>
> Happy reviewing!
>
> Paul Kocialkowski (14):
> phy: Distinguish between Rx and Tx for MIPI D-PHY with submodes
> phy: allwinner: phy-sun6i-mipi-dphy: Support D-PHY Rx mode for MIPI
> CSI-2
> media: sun6i-csi: Support an optional dedicated memory pool
> media: sun6i-csi: Fix the image storage bpp for 10/12-bit Bayer
> formats
> media: sun6i-csi: Only configure the interface data width for parallel
> media: sun6i-csi: Support feeding from the MIPI CSI-2 controller
> dt-bindings: media: i2c: Add A31 MIPI CSI-2 bindings documentation
> media: sunxi: Add support for the A31 MIPI CSI-2 controller
> ARM: dts: sun8i: v3s: Add CSI0 camera interface node
> ARM: dts: sun8i: v3s: Add MIPI D-PHY and MIPI CSI-2 interface nodes
> dt-bindings: media: i2c: Add A83T MIPI CSI-2 bindings documentation
> media: sunxi: Add support for the A83T MIPI CSI-2 controller
> ARM: dts: sun8i: a83t: Add MIPI CSI-2 controller node
> media: sunxi: sun8i-a83t-mipi-csi2: Avoid using the (unsolicited)
> interrupt
>
> .../media/allwinner,sun6i-a31-mipi-csi2.yaml | 168 +++++
> .../media/allwinner,sun8i-a83t-mipi-csi2.yaml | 158 +++++
> arch/arm/boot/dts/sun8i-a83t.dtsi | 26 +
> arch/arm/boot/dts/sun8i-v3s.dtsi | 62 ++
> drivers/media/platform/sunxi/Kconfig | 2 +
> drivers/media/platform/sunxi/Makefile | 2 +
> .../platform/sunxi/sun6i-csi/sun6i_csi.c | 54 +-
> .../platform/sunxi/sun6i-csi/sun6i_csi.h | 20 +-
> .../platform/sunxi/sun6i-mipi-csi2/Kconfig | 11 +
> .../platform/sunxi/sun6i-mipi-csi2/Makefile | 4 +
> .../sunxi/sun6i-mipi-csi2/sun6i_mipi_csi2.c | 635 +++++++++++++++++
> .../sunxi/sun6i-mipi-csi2/sun6i_mipi_csi2.h | 116 +++
> .../sunxi/sun8i-a83t-mipi-csi2/Kconfig | 11 +
> .../sunxi/sun8i-a83t-mipi-csi2/Makefile | 4 +
> .../sun8i-a83t-mipi-csi2/sun8i_a83t_dphy.c | 92 +++
> .../sun8i-a83t-mipi-csi2/sun8i_a83t_dphy.h | 39 ++
> .../sun8i_a83t_mipi_csi2.c | 660 ++++++++++++++++++
> .../sun8i_a83t_mipi_csi2.h | 196 ++++++
> drivers/phy/allwinner/phy-sun6i-mipi-dphy.c | 164 ++++-
> drivers/staging/media/rkisp1/rkisp1-isp.c | 3 +-
> include/linux/phy/phy-mipi-dphy.h | 13 +
> 21 files changed, 2408 insertions(+), 32 deletions(-)
> create mode 100644 Documentation/devicetree/bindings/media/allwinner,sun6i-a31-mipi-csi2.yaml
> create mode 100644 Documentation/devicetree/bindings/media/allwinner,sun8i-a83t-mipi-csi2.yaml
> create mode 100644 drivers/media/platform/sunxi/sun6i-mipi-csi2/Kconfig
> create mode 100644 drivers/media/platform/sunxi/sun6i-mipi-csi2/Makefile
> create mode 100644 drivers/media/platform/sunxi/sun6i-mipi-csi2/sun6i_mipi_csi2.c
> create mode 100644 drivers/media/platform/sunxi/sun6i-mipi-csi2/sun6i_mipi_csi2.h
> create mode 100644 drivers/media/platform/sunxi/sun8i-a83t-mipi-csi2/Kconfig
> create mode 100644 drivers/media/platform/sunxi/sun8i-a83t-mipi-csi2/Makefile
> create mode 100644 drivers/media/platform/sunxi/sun8i-a83t-mipi-csi2/sun8i_a83t_dphy.c
> create mode 100644 drivers/media/platform/sunxi/sun8i-a83t-mipi-csi2/sun8i_a83t_dphy.h
> create mode 100644 drivers/media/platform/sunxi/sun8i-a83t-mipi-csi2/sun8i_a83t_mipi_csi2.c
> create mode 100644 drivers/media/platform/sunxi/sun8i-a83t-mipi-csi2/sun8i_a83t_mipi_csi2.h
>