linux-kernel - Re: [PATCH 1/2] media: rcar-csi2: Fix registering camera endpoint to VIN

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Date:   Sat, 7 Mar 2020 13:03:04 +0000
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Niklas <niklas.soderlund@...natech.se>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media <linux-media@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH 1/2] media: rcar-csi2: Fix registering camera endpoint to VIN

Hi Niklas,

Thank you for the review.

On Wed, Mar 4, 2020 at 8:47 PM Niklas <niklas.soderlund@...natech.se> wrote:
>
> Hi Lad,
>
> Thanks for your work.
>
> On 2020-02-28 16:50:10 +0000, Lad Prabhakar wrote:
> > CSI2 registers camera/sensor as v4l2 async sub device with fwnode is
> > remote endpoint and the camera/sensor register itself as v4l2 sub device
> > with fwnode is remote device as a result the match.fwnode should be
> > fwnode_graph_get_remote_port_parent and not
> > fwnode_graph_get_remote_endpoint.
> >
> > This patch makes use of v4l2 helper function
> > v4l2_async_notifier_add_fwnode_remote_subdev() which uses
> > fwnode_graph_get_remote_port_parent as match.fwnode fixing the issue
> > of registering camera endpoint to the driver.
> >
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
>
> I'm afraid this is not the right solution. The rcar-csi2 driver uses the
> v4l2-async framework to do endpoint matching instead of node matching.
> This is needed as it needs to work with the adv748x driver which
> register it self in v4l2-async using endpoints instead of nodes. The
> reason for this is that from a single DT node it creates multiple
> subdevices, one for each endpoint IIRC.
>
> Without this patch the two CSI-2 receivers on R-Car M3-n registers the
> two following 'paths' in v4l2 to be able to find the two subdevice CSI-2
> transmitters created by the ADV748x.
>
> rcar-csi2 fea80000.csi2: '/soc/i2c@...d8000/video-receiver@...port@...ndpoint'
> rcar-csi2 feaa0000.csi2: '/soc/i2c@...d8000/video-receiver@...port@...ndpoint'
>
> With this patch applied it registers the following which can't be found
> as they are not present in the v4l2-async list of subdevices (as they
> are registerd as above).
>
> rcar-csi2 fea80000.csi2: '/soc/i2c@...d8000/video-receiver@70'
> rcar-csi2 feaa0000.csi2: '/soc/i2c@...d8000/video-receiver@70'
> rcar-csi2: probe of feaa0000.csi2 failed with error -17
>
> This patch may unlock your use-case as it's a known problem that
> endpoint and node matching do not mix. But it will break the already
> upstream use-case and for that reason, I'm really sorry about this.
>
Completely missed it, thank you for pointing out.

> Nacked-by: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
>
> The real solution to this problem IMHO is to make all of v4l2-async
> operate using endpoint matching or possibly some kind of fallback to
> node matching if no endpoint can be found. Never the less some work is
> required in the v4l2-async core to sort out node and endpoint matching
> coexistence.
>
Thank you for the pointers, I shall do some digging in v4l2-asyn.

Cheers,
--Prabhakar

> > ---
> >  drivers/media/platform/rcar-vin/rcar-csi2.c | 14 ++++++--------
> >  1 file changed, 6 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/media/platform/rcar-vin/rcar-csi2.c b/drivers/media/platform/rcar-vin/rcar-csi2.c
> > index faa9fb23a2e9..5b04e4768eb1 100644
> > --- a/drivers/media/platform/rcar-vin/rcar-csi2.c
> > +++ b/drivers/media/platform/rcar-vin/rcar-csi2.c
> > @@ -833,20 +833,18 @@ static int rcsi2_parse_dt(struct rcar_csi2 *priv)
> >               return ret;
> >       }
> >
> > -     priv->asd.match.fwnode =
> > -             fwnode_graph_get_remote_endpoint(of_fwnode_handle(ep));
> > -     priv->asd.match_type = V4L2_ASYNC_MATCH_FWNODE;
> > -
> > -     of_node_put(ep);
> > -
> >       v4l2_async_notifier_init(&priv->notifier);
> >
> > -     ret = v4l2_async_notifier_add_subdev(&priv->notifier, &priv->asd);
> > +     ret = v4l2_async_notifier_add_fwnode_remote_subdev(&priv->notifier,
> > +                                                        of_fwnode_handle(ep),
> > +                                                        &priv->asd);
> >       if (ret) {
> > -             fwnode_handle_put(priv->asd.match.fwnode);
> > +             of_node_put(ep);
> >               return ret;
> >       }
> >
> > +     of_node_put(ep);
> > +
> >       priv->notifier.ops = &rcar_csi2_notify_ops;
> >
> >       dev_dbg(priv->dev, "Found '%pOF'\n",
> > --
> > 2.20.1
> >
>
> --
> Regards,
> Niklas Söderlund