linux-kernel - Re: [PATCH v10 2/3] media: rockchip: Add a driver for Rockchip's camera interface

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Date:   Wed, 15 Nov 2023 10:16:20 +0100
From:   Mehdi Djait <mehdi.djait@...tlin.com>
To:     Michael Riesch <michael.riesch@...fvision.net>
Cc:     mchehab@...nel.org, heiko@...ech.de, hverkuil-cisco@...all.nl,
        krzysztof.kozlowski+dt@...aro.org, robh+dt@...nel.org,
        conor+dt@...nel.org, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        thomas.petazzoni@...tlin.com, alexandre.belloni@...tlin.com,
        maxime.chevallier@...tlin.com, paul.kocialkowski@...tlin.com
Subject: Re: [PATCH v10 2/3] media: rockchip: Add a driver for Rockchip's
 camera interface

On Mon, Nov 13, 2023 at 05:05:12PM +0100, Michael Riesch wrote:
> Hi Mehdi,
> 
> On 11/13/23 16:28, Mehdi Djait wrote:
> > Hi Michael,
> > 
> > On Fri, Nov 10, 2023 at 03:33:34PM +0100, Michael Riesch wrote:
> >> Hi Mehdi,
> >>
> >> Sorry, forgot one thing:
> >>
> >> On 11/8/23 17:38, Mehdi Djait wrote:
> >>> +static int cif_subdev_notifier(struct cif_device *cif_dev)
> >>> +{
> >>> +	struct v4l2_async_notifier *ntf = &cif_dev->notifier;
> >>> +	struct device *dev = cif_dev->dev;
> >>> +	struct v4l2_async_connection *asd;
> >>> +	struct v4l2_fwnode_endpoint vep = {
> >>> +		.bus_type = V4L2_MBUS_PARALLEL,
> >>
> >> This is surprising. I had to set this to V4L2_MBUS_UNKNOWN, otherwise
> >> v4l2_fwnode_endpoint_parse would yield -ENXIO, which indicates a bus
> >> type mismatch. Does this really work for your (BT.656, right?) setup?
> >>
> > 
> > Yes it works.
> > 
> >> I think we should get the bus type from the device tree, right?
> >>
> > 
> > I am looking into this.
> > 
> >> Thanks and best regards,
> >> Michael
> >>
> > 
> > I assume you have a "bus-type = <MEDIA_BUS_TYPE_BT656>;" in the device
> > tree definition of your endpoint ? This caused the mismatch as the
> > v4l2_fwnode_endpoint is set to PARALLEL
> 
> Yes that's correct.
> 
> The documentation is quite sparse here, but I would guess that the PX30
> VIP accepts parallel data without embedded syncs (=
> MEDIA_BUS_TYPE_PARALLEL) as well as parallel data with embedded syncs (=
> MEDIA_BUS_TYPE_BT656). If this is actually the case, I think we should
> put V4L2_MBUS_UNKNOWN and let the device tree decide.

Yes, I will do this.

> 
> We can be sure, however, that the PX30 VIP supports BT.656, so I guess
> the safe approach would be to use .bus_type = V4L2_MBUS_BT656.
> 
> What do you think?

I agree

--
Kind Regards
Mehdi Djait

> 
> Best regards,
> Michael