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Date:   Wed, 3 Oct 2018 13:42:51 +0300
From:   Sakari Ailus <sakari.ailus@linux.intel.com>
To:     Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Cc:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Hans Verkuil <hans.verkuil@cisco.com>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-media <linux-media@vger.kernel.org>, jacopo@jmondi.org,
        phdm@macq.eu, devicetree@vger.kernel.org
Subject: Re: [PATCH v4 1/2] [media] imx214: device tree binding
Message-ID: <20181003104251.ly3uusi4lqbeqize@paasikivi.fi.intel.com>
References: <20181002140515.16299-1-ricardo.ribalda@gmail.com>
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 <CAPybu_02_hMAVWO2r1-t+S60HPaqEtnQzgF-Moxg7Zx+-PGj6A@mail.gmail.com>
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On Wed, Oct 03, 2018 at 08:23:43AM +0200, Ricardo Ribalda Delgado wrote:
> Hi Laurent
> On Tue, Oct 2, 2018 at 10:06 PM Laurent Pinchart
> <laurent.pinchart@ideasonboard.com> wrote:
> >
> > Hi Ricardo,
> >
> > Thank you for the patch.
> >
> > On Tuesday, 2 October 2018 17:05:15 EEST Ricardo Ribalda Delgado wrote:
> > > Document bindings for imx214 camera sensor
> > >
> > > Cc: devicetree@vger.kernel.org
> > > Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
> > > ---
> > > Changelog from v3:
> > >
> > > Sakari Ailus:
> > > -s/should/shall/
> > > -remove clock-lanes
> > >
> > > Philippe De Muyter:
> > > -s/imx274/imx214/
> > >
> > > Laurent Pinchart:
> > > -s/to to/to/
> > > -Better description of lanes
> > > -clock-names: Shall be "xclk"
> > > -Drop clock-freq
> > >
> > >  .../devicetree/bindings/media/i2c/imx214.txt  | 53 +++++++++++++++++++
> > >  1 file changed, 53 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/media/i2c/imx214.txt
> > >
> > > diff --git a/Documentation/devicetree/bindings/media/i2c/imx214.txt
> > > b/Documentation/devicetree/bindings/media/i2c/imx214.txt new file mode
> > > 100644
> > > index 000000000000..421a019ab7f9
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/media/i2c/imx214.txt
> > > @@ -0,0 +1,53 @@
> > > +* Sony 1/3.06-Inch 13.13Mp CMOS Digital Image Sensor
> > > +
> > > +The Sony imx214 is a 1/3.06-inch CMOS active pixel digital image sensor
> > > with +an active array size of 4224H x 3200V. It is programmable through an
> > > I2C +interface. The I2C address can be configured to 0x1a or 0x10,
> > > depending on +how the hardware is wired.
> > > +Image data is sent through MIPI CSI-2, through 2 or 4 lanes at a maximum
> > > +throughput of 1.2Gbps/lane.
> > > +
> > > +
> > > +Required Properties:
> > > +- compatible: value should be "sony,imx214" for imx214 sensor
> > > +- reg: I2C bus address of the device
> > > +- enable-gpios: GPIO descriptor for the enable pin.
> > > +- vdddo-supply: Chip digital IO regulator (1.8V).
> > > +- vdda-supply: Chip analog regulator (2.7V).
> > > +- vddd-supply: Chip digital core regulator (1.12V).
> > > +- clocks: Reference to the xclk clock.
> > > +- clock-names:  Shall be "xclk".
> > > +
> > > +Optional Properties:
> > > +- flash-leds: See ../video-interfaces.txt
> > > +- lens-focus: See ../video-interfaces.txt
> > > +
> > > +The imx214 device node shall contain one 'port' child node with
> > > +an 'endpoint' subnode. For further reading on port node refer to
> > > +Documentation/devicetree/bindings/media/video-interfaces.txt.
> > > +
> > > +Required Properties on endpoint:
> > > +- data-lanes: check ../video-interfaces.txt
> >
> > As I suppose you got access to the datasheet which doesn't appear to be
> > public, I'll take this as an opportunity to fish for information :-) Does the
> > sensor support remapping data lanes ? Could you please document that here ?
> >
> > You should also state that only the 2 lanes and 4 lanes options are valid, and
> > what lanes can be used in those cases. I assume that would be <1 2> and <1 2 3
> > 4>, but if other options are possible, it would be useful to document that.
> 
> I wish I had. This is the best documentation that I got access to,
> after a lot of googling:
> http://www.ahdsensor.com/downloadRepository/3acdda8d-b531-4a76-a27d-9dd09be980ee.pdf
> 
> I never understood this secrecy around datasheets. How the f*&& are we
> going to buy chips and make desings around them if we cannot get
> information?! Sorry that was my daily vent
> 
> The 2 and 4 lane option was obtained from the functional description
> of the chip (page 1). The obvious order would be <1 2>, but I have
> also seen <1 3> in other chips, so I rather not mention it on the
> devicetree doc.

<1 3> makes sense if lane remapping is supported by the hardware. If it's
not, you should use a monotonically incrementing sequence.

-- 
Sakari Ailus
sakari.ailus@linux.intel.com