linux-kernel - RE: [v4 1/6] dt-bindings: media: Document bindings for DW MIPI CSI-2 Host

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Message-ID: <MN2PR12MB371026A6547B449EEC0439B1CBF00@MN2PR12MB3710.namprd12.prod.outlook.com>
Date:   Wed, 10 Jul 2019 10:20:55 +0000
From:   Luis de Oliveira <Luis.Oliveira@...opsys.com>
To:     Sakari Ailus <sakari.ailus@....fi>,
        Luis de Oliveira <Luis.Oliveira@...opsys.com>
CC:     "mchehab@...nel.org" <mchehab@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "Jonathan.Cameron@...wei.com" <Jonathan.Cameron@...wei.com>,
        "robh@...nel.org" <robh@...nel.org>,
        "nicolas.ferre@...rochip.com" <nicolas.ferre@...rochip.com>,
        "paulmck@...ux.ibm.com" <paulmck@...ux.ibm.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "kishon@...com" <kishon@...com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Joao.Pinto@...opsys.com" <Joao.Pinto@...opsys.com>
Subject: RE: [v4 1/6] dt-bindings: media: Document bindings for DW MIPI CSI-2
 Host

Hi Sakari,

From: Sakari Ailus <sakari.ailus@....fi>
Date: Tue, Jul 09, 2019 at 19:25:00

> Hi Luis,
> 
> On Mon, Jul 08, 2019 at 03:21:50PM +0000, Luis de Oliveira wrote:
> > Hi Sakari,
> > 
> > Thank you for your feedback.
> > I have my comments inline.
> > 
> > From: Sakari Ailus <sakari.ailus@....fi>
> > Date: Fri, Jun 28, 2019 at 15:13:26
> > 
> > > Hi Luis,
> > > 
> > > Thank you for the patchset.
> > > 
> > > On Tue, Jun 11, 2019 at 09:20:50PM +0200, Luis Oliveira wrote:
> > > > From: Luis Oliveira <lolivei@...opsys.com>
> > > > 
> > > > Add bindings for Synopsys DesignWare MIPI CSI-2 host.
> > > > 
> > > > Signed-off-by: Luis Oliveira <lolivei@...opsys.com>
> > > > ---
> > > > Changelog
> > > > v3-v4
> > > > - remove "plat" from the block name @rob @laurent
> > > > - remove "phy-names" when single-entry @rob
> > > > - remove "snps,output-type" -> went to the driver config @laurent
> > > > 
> > > >  .../devicetree/bindings/media/snps,dw-csi.txt      | 41 ++++++++++++++++++++++
> > > >  1 file changed, 41 insertions(+)
> > > >  create mode 100644 Documentation/devicetree/bindings/media/snps,dw-csi.txt
> > > > 
> > > > diff --git a/Documentation/devicetree/bindings/media/snps,dw-csi.txt b/Documentation/devicetree/bindings/media/snps,dw-csi.txt
> > > > new file mode 100644
> > > > index 0000000..613b7f9
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/media/snps,dw-csi.txt
> > > > @@ -0,0 +1,41 @@
> > > > +Synopsys DesignWare CSI-2 Host controller
> > > > +
> > > > +Description
> > > > +-----------
> > > > +
> > > > +This HW block is used to receive image coming from an MIPI CSI-2 compatible
> > > > +camera.
> > > > +
> > > > +Required properties:
> > > > +- compatible		: shall be "snps,dw-csi"
> > > > +- reg			: physical base address and size of the device memory
> > > > +			  mapped registers;
> > > > +- interrupts		: DW CSI-2 Host interrupts
> > > > +- phys			: List of one PHY specifier (as defined in
> > > > +			  Documentation/devicetree/bindings/phy/phy-bindings.txt).
> > > > +			  This PHY is a MIPI DPHY working in RX mode.
> > > > +- resets		: Reference to a reset controller (optional)
> > > > +
> > > > +The per-board settings:
> > > > + - port sub-node describing a single endpoint connected to the camera as
> > > > +   described in video-interfaces.txt[1].
> > > 
> > > Which endpoint properties in video-interfaces.txt are relevant for the
> > > hardware? Which values may they have?
> > > 
> > 
> > Currently I'm using only two properties "data-lanes" and "bus-width", but 
> > I have plans to add blanking info also.
> > I will add more info.
> 
> Isn't blanking defined by what the transmitter seneds? Or do you have
> hardware limitations on the receiver side?
> 

When we use this IP in prototyping we configure blanking at the receiver 
side.
Some cameras don't have blanking configuration capabilities so we 
configure it on the RX side.

> I've only heard of one such case before, and it was a very old parallel
> receiver.
> 
> If you have a CSI-2 receiver, bus-width isn't relevant --- it's for paralle
> interfaces only. Please add data-lanes to required endpoint properties.
> 

I used bus-width property in the Synopsys IPI (Image Pixel Interface) 
that enables direct video stream access.
This interface is an output that can be 16-bit or 48-bit, that's why I 
used bus-width property.

> -- 
> Regards,
> 
> Sakari Ailus

Thank you,
Luis