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Message-ID: <20210118223636.GA3@valkosipuli.retiisi.org.uk>
Date: Tue, 19 Jan 2021 00:40:28 +0200
From: Sakari Ailus <sakari.ailus@....fi>
To: AngeloGioacchino Del Regno
<angelogioacchino.delregno@...ainline.org>
Cc: mchehab@...nel.org, robh+dt@...nel.org, shawnguo@...nel.org,
s.hauer@...gutronix.de, linux-media@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
phone-devel@...r.kernel.org, konrad.dybcio@...ainline.org,
marijn.suijten@...ainline.org, martin.botka@...ainline.org
Subject: Re: [PATCH v4 2/2] media: dt-bindings: media: i2c: Add IMX300 CMOS
sensor binding
On Sun, Jan 17, 2021 at 06:51:04PM +0100, AngeloGioacchino Del Regno wrote:
> Il 17/01/21 00:44, Sakari Ailus ha scritto:
> > Hi AngeloGioacchino,
> >
> > On Wed, Jan 13, 2021 at 07:29:34PM +0100, AngeloGioacchino Del Regno wrote:
> > > Add YAML device tree binding for IMX300 CMOS image sensor, and
> > > the relevant MAINTAINERS entries.
> > >
> > > Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...ainline.org>
> > > ---
> > > .../bindings/media/i2c/sony,imx300.yaml | 112 ++++++++++++++++++
> > > MAINTAINERS | 7 ++
> > > 2 files changed, 119 insertions(+)
> > > create mode 100644 Documentation/devicetree/bindings/media/i2c/sony,imx300.yaml
> > >
> > > diff --git a/Documentation/devicetree/bindings/media/i2c/sony,imx300.yaml b/Documentation/devicetree/bindings/media/i2c/sony,imx300.yaml
> > > new file mode 100644
> > > index 000000000000..4fa767feea80
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/media/i2c/sony,imx300.yaml
> > > @@ -0,0 +1,112 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/media/i2c/sony,imx300.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Sony 1/2.3-Inch 25Mpixel Stacked CMOS Digital Image Sensor
> > > +
> > > +maintainers:
> > > + - AngeloGioacchino Del Regno <angelogioacchino.delregno@...ainline.org>
> > > +
> > > +description: |-
> > > + The Sony IMX300 is a 1/2.3-inch Stacked CMOS (Exmor-RS) digital image
> > > + sensor with a pixel size of 1.08um and an active array size of
> > > + 5948H x 4140V. It is programmable through I2C interface at address 0x10.
> > > + Image data is sent through MIPI CSI-2, which is configured as either 2 or
> > > + 4 data lanes.
> > > +
> > > +properties:
> > > + compatible:
> > > + const: sony,imx300
> > > +
> > > + reg:
> > > + maxItems: 1
> > > +
> > > + clocks:
> > > + maxItems: 1
> >
> > Please add assigned clock related properties; see
> > Documentation/driver-api/media/camera-sensor.rst .
> >
> Will do!
>
> > > +
> > > + vdig-supply:
> > > + description:
> > > + Digital I/O voltage supply, 1.15-1.20 volts
> > > +
> > > + vana-supply:
> > > + description:
> > > + Analog voltage supply, 2.2 volts
> > > +
> > > + vddl-supply:
> > > + description:
> > > + Digital core voltage supply, 1.8 volts
> > > +
> > > + reset-gpios:
> > > + description: |-
> > > + Reference to the GPIO connected to the xclr pin, if any.
> > > + Must be released (set high) after all supplies are applied.
> > > +
> > > + # See ../video-interfaces.txt for more details
> > > + port:
> > > + type: object
> > > + properties:
> > > + endpoint:
> > > + type: object
> > > +
> > > + properties:
> > > + data-lanes:
> > > + description: |-
> > > + The driver only supports four-lane operation.
> >
> > This can be removed as bindings describe hardware, not driver operation.
> >
> Ack.
>
> > > + items:
> > > + - const: 0
> > > + - const: 1
> > > + - const: 2
> > > + - const: 3
> >
> > Two lanes here, too?
> >
>
> The driver only supports four-lane operation.
> I am 100% sure that this sensor can also work with two lanes, but it needs
> special configuration which I'm not able to produce, nor test.
>
> As you may imagine (and as you can read in the driver itself), all of this
> was reverse-engineering work, as Sony has never released any datasheet for
> this sensor - and I have a hunch - they never will (but that's another
> story).
That's all fine. The bindings describe the hardware, not the driver's
capabilities.
>
> > > +
> > > + clock-noncontinuous: true
> > > +
> > > + link-frequencies:
> > > + $ref: /schemas/types.yaml#/definitions/uint64-array
> > > + description:
> > > + Allowed data bus frequencies. The driver currently needs
> > > + to switch between 780000000 and 480000000 Hz in order to
> > > + guarantee functionality of all modes.
> >
> > You can omit this description, too.
> >
>
> The intention here was to be clear and provide as much information as I
> could gather during the very time-consuming reverse engineering process that
> took place in the making of this driver.
>
> But okay, I will remove this.
Again, this is about the hardware, not the driver. That information is also
part of the driver.
>
> > > +
> > > + required:
> > > + - data-lanes
> > > + - link-frequencies
> > > +
> > > +required:
> > > + - compatible
> > > + - reg
> > > + - clocks
> > > + - vana-supply
> > > + - vdig-supply
> > > + - vddl-supply
> >
> > Are the regulators really required? I'm not quite sure about the
> > established practices; still the common case is that one or two of these
> > are hard-wired.
> >
>
> On all the Sony phones that I have (....many), with MSM8956, MSM8996,
> SDM630, equipped with the IMX300 camera assy, none of these three are
> hard-wired: sometimes they're wired to the LDOs of the PMIC, sometimes
> they're wired to fixed LDOs, enabled through GPIOs (fixed-regulator binding
> in this case).
>
> So.. yeah, they're really required.
As noted, that depends on the board. You just happen to have some where
they are not hard-wired.
>
> > > + - port
> > > +
> > > +additionalProperties: false
> > > +
> > > +examples:
> > > + - |
> > > + i2c0 {
> > > + #address-cells = <1>;
> > > + #size-cells = <0>;
> > > +
> > > + imx300: sensor@10 {
> > > + compatible = "sony,imx300";
> > > + reg = <0x10>;
> > > + clocks = <&imx300_xclk>;
> > > + vana-supply = <&imx300_vana>; /* 2.2v */
> > > + vdig-supply = <&imx300_vdig>; /* 1.2v */
> > > + vddl-supply = <&imx300_vddl>; /* 1.8v */
> > > +
> > > + port {
> > > + imx300_0: endpoint {
> > > + remote-endpoint = <&csi1_ep>;
> > > + data-lanes = <0 1 2 3>;
> > > + clock-noncontinuous;
> > > + link-frequencies = /bits/ 64 <780000000 480000000>;
> > > + };
> > > + };
> > > + };
> > > + };
> > > +
> > > +...
> > > diff --git a/MAINTAINERS b/MAINTAINERS
> > > index ad9abb42f852..5e0f08f48d48 100644
> > > --- a/MAINTAINERS
> > > +++ b/MAINTAINERS
> > > @@ -16633,6 +16633,13 @@ T: git git://linuxtv.org/media_tree.git
> > > F: Documentation/devicetree/bindings/media/i2c/imx290.txt
> > > F: drivers/media/i2c/imx290.c
> > > +SONY IMX300 SENSOR DRIVER
> > > +M: AngeloGioacchino Del Regno <angelogioacchino.delregno@...ainline.org>
> > > +L: linux-media@...r.kernel.org
> >
> > Please also add the git tree.
> >
> > Ideally also the MAINTAINERS change comes with the first patch adding the
> > files, which should be the DT bindings. I.e. just reverse the order of the
> > patches.
> >
>
> I haven't added it because last time I did that I got reviews saying that if
> I'm not the owner of the git tree I shall not put it in.
> Though, if that's a requirement for media, then I didn't know that...
The documentation in MAINTAINERS doesn't say that at least.
I think it'd be useful to have it.
>
> > > +S: Maintained
> > > +F: Documentation/devicetree/bindings/media/i2c/sony,imx300.yaml
> > > +F: drivers/media/i2c/imx300.c
> > > +
> > > SONY IMX319 SENSOR DRIVER
> > > M: Bingbu Cao <bingbu.cao@...el.com>
> > > L: linux-media@...r.kernel.org
> >
>
> Thank you for your review!
You're welcome!
--
Sakari Ailus
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