Re: [V7, 1/2] media: dt-bindings: media: i2c: Document OV02A10 bindings

[Dongchun Zhu <dongchun.zhu@mediatek.com>]

Hi Sakari,

Thanks for the review.

On Wed, 2020-05-06 at 14:21 +0300, Sakari Ailus wrote:
> Hi Dongchun,
> 
> On Tue, May 05, 2020 at 10:17:18PM +0800, Dongchun Zhu wrote:
> > Hi Sakari,
> > 
> > Thanks for the review.
> > 
> > On Tue, 2020-05-05 at 10:04 +0300, Sakari Ailus wrote:
> > > Hi Dongchun,
> > > 
> > > On Thu, Apr 30, 2020 at 04:09:23PM +0800, Dongchun Zhu wrote:
> > > > Add DT bindings documentation for Omnivision OV02A10 image sensor.
> > > > 
> > > > Signed-off-by: Dongchun Zhu <dongchun.zhu@mediatek.com>
> > > > ---
> > > >  .../bindings/media/i2c/ovti,ov02a10.yaml           | 148 +++++++++++++++++++++
> > > >  MAINTAINERS                                        |   7 +
> > > >  2 files changed, 155 insertions(+)
> > > >  create mode 100644 Documentation/devicetree/bindings/media/i2c/ovti,ov02a10.yaml
> > > > 
> > > > diff --git a/Documentation/devicetree/bindings/media/i2c/ovti,ov02a10.yaml b/Documentation/devicetree/bindings/media/i2c/ovti,ov02a10.yaml
> > > > new file mode 100644
> > > > index 0000000..2be4bd2
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/media/i2c/ovti,ov02a10.yaml
> > > > @@ -0,0 +1,148 @@
> > > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > > > +# Copyright (c) 2020 MediaTek Inc.
> > > > +%YAML 1.2
> > > > +---
> > > > +$id: http://devicetree.org/schemas/media/i2c/ovti,ov02a10.yaml#
> > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > +
> > > > +title: Omnivision OV02A10 CMOS Sensor Device Tree Bindings
> > > > +
> > > > +maintainers:
> > > > +  - Dongchun Zhu <dongchun.zhu@mediatek.com>
> > > > +
> > > > +description: |-
> > > > +  The Omnivision OV02A10 is a low-cost, high performance, 1/5-inch, 2 megapixel
> > > > +  image sensor, which is the latest production derived from Omnivision's CMOS
> > > > +  image sensor technology. Ihis chip supports high frame rate speeds up to 30fps
> > > > +  @ 1600x1200 (UXGA) resolution transferred over a 1-lane MIPI interface. The
> > > > +  sensor output is available via CSI-2 serial data output.
> > > > +
> > > > +properties:
> > > > +  compatible:
> > > > +    const: ovti,ov02a10
> > > > +
> > > > +  reg:
> > > > +    maxItems: 1
> > > > +
> > > > +  clocks:
> > > > +    items:
> > > > +      - description: top mux camtg clock
> > > > +      - description: devider clock
> > > > +
> > > > +  clock-names:
> > > > +    items:
> > > > +      - const: eclk
> > > > +      - const: freq_mux
> > > > +
> > > > +  clock-frequency:
> > > > +    description:
> > > > +      Frequency of the eclk clock in Hertz.
> > > > +
> > > > +  dovdd-supply:
> > > > +    description:
> > > > +      Definition of the regulator used as interface power supply.
> > > > +
> > > > +  avdd-supply:
> > > > +    description:
> > > > +      Definition of the regulator used as analog power supply.
> > > > +
> > > > +  dvdd-supply:
> > > > +    description:
> > > > +      Definition of the regulator used as digital power supply.
> > > > +
> > > > +  powerdown-gpios:
> > > > +    description:
> > > > +      The phandle and specifier for the GPIO that controls sensor powerdown.
> > > > +
> > > > +  reset-gpios:
> > > > +    description:
> > > > +      The phandle and specifier for the GPIO that controls sensor reset.
> > > > +
> > > > +  rotation:
> > > > +    description:
> > > > +      Definition of the sensor's placement, valid values are 0 and 180.
> > > > +    allOf:
> > > > +      - $ref: "/schemas/types.yaml#/definitions/uint32"
> > > > +      - enum:
> > > > +          - 0    # Sensor Mounted Upright
> > > > +          - 180  # Sensor Mounted Upside Down
> > > > +
> > > > +  ovti,mipi-tx-speed:
> > > > +    description:
> > > > +      Indication of MIPI transmission speed select.
> > > 
> > > What exactly does this signify? And how do you come up with the number?
> > > 
> > 
> > Apologies for not addressing this number clear.
> > 
> > From the datasheet, P1:0xA1 register represents TX_SPEED_AREA_SEL with
> > the default val: 0x03.
> > The description of this RW register is as below:
> > Bit[2:0]: MIPI transmission speed select.
> > 
> > Thus the enum should be definited as [ 0, 1, 2, 3, 4, 5, 6, 7 ].
> > This would be fixed in next release.
> > 
> > In the meantime, as the default val of P1:0xA1 is 0x03, we hope to keep
> > that value if there is no setting for this private property in DT.
> > The caller in driver would be updated like this in next release.
> > if (ov02a10->mipi_clock_tx_speed)
> > 	ret = i2c_smbus_write_byte_data(...,...);
> 
> How did you pick the value in the example? And why do you believe it is
> specific to a platform, and not e.g. a sensor mode?
> 

We look into P1:0XA1, one register that defines MIPI transmission speed
select.
From the datasheet, we can get the possible values that could be set to
P1:0xA1.

Actually this register is an independent of sensor mode, it is just
included in sensor mode's register setting table.

In addition, this private DT Property is created to fix the MIPI test
failure. The register values are adjusted and verified from vendor to
make sensor signal meet MIPI specification.

> > 
> > > > +    allOf:
> > > > +      - $ref: "/schemas/types.yaml#/definitions/uint32"
> > > > +      - enum: [ 3, 4 ]
> > > > +
> > > > +  # See ../video-interfaces.txt for details
> > > > +  port:
> > > > +    type: object
> > > > +    additionalProperties: false
> > > > +
> > > > +    properties:
> > > > +      endpoint:
> > > > +        type: object
> > > > +        additionalProperties: false
> > > > +
> > > > +        properties:
> > > > +          remote-endpoint: true
> > > > +          link-frequencies: true
> > > > +
> > > > +    required:
> > > > +      - endpoint
> > > > +
> > > > +required:
> > > > +  - compatible
> > > > +  - reg
> > > > +  - clocks
> > > > +  - clock-names
> > > > +  - clock-frequency
> > > > +  - dovdd-supply
> > > > +  - avdd-supply
> > > > +  - dvdd-supply
> > > > +  - powerdown-gpios
> > > > +  - reset-gpios
> > > > +  - port
> > > > +
> > > > +additionalProperties: false
> > > > +
> > > > +examples:
> > > > +  - |
> > > > +    #include <dt-bindings/clock/mt8183-clk.h>
> > > > +    #include <dt-bindings/gpio/gpio.h>
> > > > +
> > > > +    i2c {
> > > > +        clock-frequency = <400000>;
> > > > +        #address-cells = <1>;
> > > > +        #size-cells = <0>;
> > > > +
> > > > +        ov02a10: camera-sensor@3d {
> > > > +            compatible = "ovti,ov02a10";
> > > > +            reg = <0x3d>;
> > > > +            pinctrl-names = "default";
> > > > +            pinctrl-0 = <&clk_24m_cam>;
> > > > +
> > > > +            clocks = <&topckgen CLK_TOP_MUX_CAMTG>,
> > > > +                     <&topckgen CLK_TOP_UNIVP_192M_D8>;
> > > > +            clock-names = "eclk", "freq_mux";
> > > > +            clock-frequency = <24000000>;
> > > > +
> > > > +            rotation = <180>;
> > > > +            ovti,mipi-tx-speed = <3>;
> > > > +
> > > > +            dovdd-supply = <&mt6358_vcamio_reg>;
> > > > +            avdd-supply = <&mt6358_vcama1_reg>;
> > > > +            dvdd-supply = <&mt6358_vcn18_reg>;
> > > > +            powerdown-gpios = <&pio 107 GPIO_ACTIVE_LOW>;
> > > > +            reset-gpios = <&pio 109 GPIO_ACTIVE_HIGH>;
> > > > +
> > > > +            port {
> > > > +                wcam_out: endpoint {
> > > > +                    remote-endpoint = <&mipi_in_wcam>;
> > > > +                    link-frequencies = /bits/ 64 <390000000>;
> > > > +                };
> > > > +            };
> > > > +        };
> > > > +    };
> > > > +
> > > > +...
> > > > diff --git a/MAINTAINERS b/MAINTAINERS
> > > > index e64e5db..63a2335 100644
> > > > --- a/MAINTAINERS
> > > > +++ b/MAINTAINERS
> > > > @@ -12389,6 +12389,13 @@ M:	Harald Welte <laforge@gnumonks.org>
> > > >  S:	Maintained
> > > >  F:	drivers/char/pcmcia/cm4040_cs.*
> > > >  
> > > > +OMNIVISION OV02A10 SENSOR DRIVER
> > > > +M:	Dongchun Zhu <dongchun.zhu@mediatek.com>
> > > > +L:	linux-media@vger.kernel.org
> > > > +S:	Maintained
> > > > +T:	git git://linuxtv.org/media_tree.git
> > > > +F:	Documentation/devicetree/bindings/media/i2c/ovti,ov02a10.yaml
> > > > +
> > > >  OMNIVISION OV13858 SENSOR DRIVER
> > > >  M:	Sakari Ailus <sakari.ailus@linux.intel.com>
> > > >  L:	linux-media@vger.kernel.org
> > > 
> > 
>