linux-kernel - Re: [PATCH v3 06/24] ARM: dts: imx6-sabrelite: add OV5642 and OV5640 camera sensors

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Message-ID: <23975350.L90NWivx6X@avalon>
Date:   Sun, 05 Feb 2017 17:24:30 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
Cc:     Steve Longerbeam <slongerbeam@...il.com>, robh+dt@...nel.org,
        mark.rutland@....com, shawnguo@...nel.org, kernel@...gutronix.de,
        fabio.estevam@....com, mchehab@...nel.org, hverkuil@...all.nl,
        nick@...anahar.org, markus.heiser@...marit.de,
        p.zabel@...gutronix.de, laurent.pinchart+renesas@...asonboard.com,
        bparrot@...com, geert@...ux-m68k.org, arnd@...db.de,
        sudipm.mukherjee@...il.com, minghsiu.tsai@...iatek.com,
        tiffany.lin@...iatek.com, jean-christophe.trotin@...com,
        horms+renesas@...ge.net.au, niklas.soderlund+renesas@...natech.se,
        robert.jarzmik@...e.fr, songjun.wu@...rochip.com,
        andrew-ct.chen@...iatek.com, gregkh@...uxfoundation.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
        devel@...verdev.osuosl.org,
        Steve Longerbeam <steve_longerbeam@...tor.com>
Subject: Re: [PATCH v3 06/24] ARM: dts: imx6-sabrelite: add OV5642 and OV5640 camera sensors

Hi Russell,

On Monday 30 Jan 2017 22:51:33 Russell King - ARM Linux wrote:
> On Fri, Jan 06, 2017 at 06:11:24PM -0800, Steve Longerbeam wrote:
> > +	ov5640: camera@40 {
> > +		compatible = "ovti,ov5640";
> > +		pinctrl-names = "default";
> > +		pinctrl-0 = <&pinctrl_ov5640>;
> > +		clocks = <&mipi_xclk>;
> > +		clock-names = "xclk";
> > +		reg = <0x40>;
> > +		xclk = <22000000>;
> > +		reset-gpios = <&gpio2 5 GPIO_ACTIVE_LOW>; /* NANDF_D5 */
> > +		pwdn-gpios = <&gpio6 9 GPIO_ACTIVE_HIGH>; /* NANDF_WP_B */
> > +
> > +		port {
> > +			#address-cells = <1>;
> > +			#size-cells = <0>;
> > +
> > +			ov5640_to_mipi_csi: endpoint@1 {
> > +				reg = <1>;
> > +				remote-endpoint = 
<&mipi_csi_from_mipi_sensor>;
> > +				data-lanes = <0 1>;
> > +				clock-lanes = <2>;
> 
> How do you envision a four-lane sensor being described?
> 
> 	data-lanes = <0 1 3 4>;
> 	clock-lanes = <2>;
> 
> ?
> 
> The binding document for video-interfaces.txt says:
> 
> - clock-lanes: an array of physical clock lane indexes. Position of an entry
> determines the logical lane number, while the value of an entry indicates
> physical lane, e.g. for a MIPI CSI-2 bus we could have "clock-lanes =
> <0>;", which places the clock lane on hardware lane 0. This property is
> valid for serial busses only (e.g. MIPI CSI-2). Note that for the MIPI
> CSI-2 bus this array contains only one entry.
> 
> So I think you need to have a good reason to make the clock lane non-zero.

The purpose of the data-lanes and clock-lanes properties is to describe lane 
assignment for hardware that supports lane routing. As far as I know the 
OV5640 doesn't support lane routing and has dedicated pins for the clock and 
data lanes. The data-lanes and clock-lanes properties should probably not be 
specified at all.

-- 
Regards,

Laurent Pinchart