Re: nxp imx8m CSI drivers

[Martin Kepplinger <martin.kepplinger@puri.sm>]

On 09.07.20 11:32, Martin Kepplinger wrote:
> hi linux-media people,
> 
> TL-DR: when exactly is "sd->entity.function == MEDIA_ENT_F_VID_MUX"?
> 
> 
> I try to use the camera on our librem5-devkit (imx8mq): I try to use
> only mainline drivers except for "mxc-mipi-csi2_yav" taken from
> linux-imx (which we can prepare to submit if a PoC works. This is the
> tree I'm experimenting with:
> 
> https://source.puri.sm/martin.kepplinger/linux-next/-/commits/5.8-rc4/librem5___csi
> 
> * "imx7-media-csi" / imx-media-capture / imx-media-utils currently in
> staging (that should work according to NXP)
> * ov5640 mainline driver
> * mxc-mipi-csi2_yav from NXP tree (linux-imx) with
> v4l2_subdev_video_ops' mipi_csis_g_parm and mipi_csis_s_parm callbacks
> removed (due to missing API in mainline)
> 
> the drivers probe and run but the following fails when trying to use the
> camera (gstreamer):
> 
> in imx-media-utils' imx_media_pipeline_set_stream() the call to
> v4l2_subdev_call(sd, video, s_stream, 1) returns with 32 (broken pipe)
> and thus the application that tries to use the camera too.
> 
> One problem is definitely the trees' last commit (that I did as a
> workaround) in this tree that makes the drivers probe but only by
> ignoring this probably needed check:
> 
> imx7-media-csi's imx7_csi_notify_bound() callback implementation gets
> called during startup. But if (WARN_ON(sd->entity.function !=
> MEDIA_ENT_F_VID_MUX)) is true so this is the wrong type of subdev (?).
> 
> I just want to put this out there and check if the general approach is
> valid at all and if there's anything that comes to your mind.
> 
> thanks a lot,
>                               martin
> 

(added Pavel Machek)

still I'm only on the librem5 Devkit: the situation regarding a tree
that should use the imx7-media-csi csi_bridge driver hasn't changed, see
above for the details. The tree I tried now is this one:

https://source.puri.sm/martin.kepplinger/linux-next/-/commits/5.8-rc7/librem5___csi_ml1

A tree that includes NXP's csi_bridge and mipi-csi drivers (and camera
driver) on the other hand works, and I have one based on v5.8-rcX too:

https://source.puri.sm/martin.kepplinger/linux-next/-/commits/5.8-rc7/librem5___csi_nxp

Since I want to look into a different camera driver, I might use that
nxp-drivers tree to work on that, but our goal is obviously to use what
is already in staging and should work (the csi bridge driver at least).
In case you know more about the v4l2 details that don't match over
there, please have a look.

thanks a lot in advance,

                               martin