Working with the OV13850 camera sensor on the NanoPC-T4

Sun Nov 15 13:41:57 EST 2020

On Sun, 15 Nov 2020 at 08:11, Sebastian Fricke
<sebastian.fricke.linux at gmail.com> wrote:
>
> Hello,
>

Hello Sebastian,

Let me first add my colleagues Helen and Dafna, who maintain this driver,
and who will surely yell if I stop making sense here.

> I am currently trying to get the OV13850 camera sensor
> (https://www.friendlyarm.com/index.php?route=product/product&product_id=228) to work on my friendlyElec NanoPC-T4.
>
> I have problems with connecting the RkISP1 ISP to the OV13850 sensor and I am not sure,
> where the problem could be. The device tree seems to load correctly and
> I can detect the sensor as a device on the i2c bus:
>
> root at nanopct4:~# cat /sys/bus/i2c/devices/1-0010/name
> ov13850
>

OK, good start :-)

> And the driver module is loaded as well:
>
> root at nanopct4:~# lsmod | grep ov13850
> ov13850                28672  0
> v4l2_fwnode            28672  2 rockchip_isp1,ov13850
> videodev              266240  9 rockchip_vdec,v4l2_fwnode,rockchip_isp1,videobuf2_v4l2,hantro_vpu,rockchip_rga,videobuf2_common,v4l2_mem2mem,ov13850
> mc                     61440  8 rockchip_vdec,videodev,rockchip_isp1,videobuf2_v4l2,hantro_vpu,videobuf2_common,v4l2_mem2mem,ov13850
>
> The driver reports using dummy regulators instead of the requested ones,
> I am not sure yet if this is part of the problem, as the driver doesn't
> bail out after requesting the regulators. But from what I currently
> understand, these warnings mean that for some reason my system didn't
> map these regulators but acts as if they were there.
>
> More info below, I hope that someone can help to find the error I made,
> thanks in advance!
>
> -----------------------------
>
> I attached the two patches I created:
> 1. For the device tree I combined a patch from Helen Koike (which is not merged yet),
>    where she adds the isp0 to the rk3399.dtsi file, with my addition which
>    activates the mipi_dphy_rx0, adds the camera sensor to i2c1 and
>    connects the pads of the ISP with the sensor. I followed the
>    documentation for the ISP part and got most of the camera sensor
>    parts from the BSP Kernel:
>    (https://github.com/friendlyarm/kernel-rockchip/blob/nanopi4-linux-v4.4.y/arch/arm64/boot/dts/rockchip/rk3399-nanopi4-rkisp1.dtsi#L52).
> 2. I ported the driver from the BSP kernel of friendlyElec:
>    (https://github.com/friendlyarm/kernel-rockchip/blob/nanopi4-linux-v4.4.y/drivers/media/i2c/ov13850.c)
>    I changed a few lines in order to have the module compile correctly.
>    ```
>     +#include <linux/compat.h>
>     -       sd->entity.type = MEDIA_ENT_T_V4L2_SUBDEV_SENSOR;
>     -       ret = media_entity_init(&sd->entity, 1, &ov13850->pad, 0);
>     +       sd->entity.function = MEDIA_ENT_F_CAM_SENSOR;
>     +       ret = media_entity_pads_init(&sd->entity, 1, &ov13850->pad);
>     ```
>

Keep in mind that, with some exceptions, the upstream community
doesn't provide much help with downstream/vendor kernels.

> ----------------------------------------
>
> I was able to create an armbian image for the media_tree (https://git.linuxtv.org/media_tree.git/):

Ah, upstream is better :-)

> root at nanopct4:~# uname -a
> Linux nanopct4 5.10.0-rc1-rockchip64 #trunk SMP PREEMPT Fri Nov 13 15:08:05 CET 2020 aarch64 GNU/Linux
>
> When I boot up the board I can spot the following messages in the kernel
> log:
> [    7.216307] ov13850 1-0010: driver version: 00.01.01
> [    7.216322] ov13850 1-0010: could not get module information!
> [    7.216565] ov13850 1-0010: supply avdd not found, using dummy regulator
> [    7.216761] ov13850 1-0010: supply dovdd not found, using dummy regulator
> [    7.216846] ov13850 1-0010: supply dvdd not found, using dummy regulator
> [    7.219535] ov13850 1-0010: Detected OV00d850 sensor, REVISION 0xb1

OK, good.

I can be wrong (since I haven't looked at your driver) but this
usually indicates
your sensor is powered and properly configured to at least read
some CHIP_ID register.

The regulators are likely always-on in your sensor module,
so maybe probably that's why it works.

See for instance arch/arm64/boot/dts/renesas/aistarvision-mipi-adapter-2.1.dtsi
for an example of how regulators can be declared. There are other ways,
it's just an example.

> ...
> [    7.352292] rockchip_isp1: module is from the staging directory, the quality is unknown, you have been warned.
> ...
> [    7.356178] rkisp1 ff910000.isp0: Adding to iommu group 4
> ...
> [    7.357637] rkisp1: registered rkisp1_mainpath as /dev/video0
> [    7.357816] rkisp1: registered rkisp1_selfpath as /dev/video1
>
> ----------------------------------------
>
> And this command (try to stream 50 frames from video1 which the mainpath
> on the RkISP1):
> root at nanopct4:~# v4l2-ctl --stream-to /home/basti/test.raw --stream-mmap 50 -d /dev/video0 --verbose
>
> I get this output:
> VIDIOC_STREAMON returned -1 (No such device)
>
> And this kernel log message:
> [16939.667867] rkisp1 ff910000.isp0: No link between isp and sensor
>

This error seems useful. It would indicate your sensor is not
connected (software-connected) to the ISP.

See below.

> -----------------------------------------
>
> Here is the output for media-ctl -p:
>
> Media controller API version 5.10.0
>
> Media device information
> ------------------------
> driver          rkisp1
> model           rkisp1
> serial
> bus info        platform:rkisp1
> hw revision     0x0
> driver version  5.10.0
>
> Device topology
> - entity 1: rkisp1_isp (4 pads, 4 links)
>             type V4L2 subdev subtype Unknown flags 0
>             device node name /dev/v4l-subdev0
>         pad0: Sink
>                 [fmt:SRGGB10_1X10/800x600 field:none
>                  crop.bounds:(0,0)/800x600
>                  crop:(0,0)/800x600]
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Note that here the rkisp1_isp entity sink pad 0
should be connected to the bayer sensor, but it
seems not connected to anything.

I can be wrong, but I don't see your sensor
appearing anywhere in the topology.

See for instance, the example in the driver
documentation:

https://www.kernel.org/doc/html/latest/admin-guide/media/rkisp1.html

And note the section where the topology is set, connecting
the imx219 sensor to rkisp1_isp sink pad0:

"media-ctl" "-d" "platform:rkisp1" "-l" "'imx219 4-0010':0 ->
'rkisp1_isp':0 [1]"

So I would say you are very much on the right track,
but you still need a bit more work to construct the capture pipeline.

Not sure if this helps, or makes things more complicated, but instead
of  v4l2-ctl, I would personally start with libcamera, and work from there.

Cheers,
Ezequiel