Re: [PATCH v4 1/2] dt-bindings: media: i2c: Add IMX296 CMOS sensor binding

Laurent Pinchart
2019-10-31T14:11:52Z

Hi Mani,

On Thu, Oct 31, 2019 at 07:15:12PM +0530, Manivannan Sadhasivam wrote:
> On Thu, Oct 31, 2019 at 03:15:38PM +0200, Laurent Pinchart wrote:
> > On Wed, Oct 30, 2019 at 03:19:01PM +0530, Manivannan Sadhasivam wrote:
> >> Add YAML devicetree binding for IMX296 CMOS image sensor. Let's also
> >> add MAINTAINERS entry for the binding and driver.
> >>
> >> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> >> ---
> >> .../devicetree/bindings/media/i2c/imx296.yaml | 94 +++++++++++++++++++
> >> MAINTAINERS | 8 ++
> >> 2 files changed, 102 insertions(+)
> >> create mode 100644 Documentation/devicetree/bindings/media/i2c/imx296.yaml
> >>
> >> diff --git a/Documentation/devicetree/bindings/media/i2c/imx296.yaml b/Documentation/devicetree/bindings/media/i2c/imx296.yaml
> >> new file mode 100644
> >> index 000000000000..c04ec2203268
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/media/i2c/imx296.yaml
> >> @@ -0,0 +1,94 @@
> >> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> >> +%YAML 1.2
> >> +---
> >> +$id: http://devicetree.org/schemas/media/i2c/imx296.yaml#
> >> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> >> +
> >> +title: Sony IMX296 1/2.8-Inch CMOS Image Sensor
> >> +
> >> +maintainers:
> >> + - Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> >> +
> >> +description: |-
> >> + The Sony IMX296 is a 1/2.9-Inch active pixel type CMOS Solid-state image
> >> + sensor with square pixel array and 1.58 M effective pixels. This chip
> >> + features a global shutter with variable charge-integration time. It is
> >> + programmable through I2C and 4-wire interfaces. The sensor output is
> >> + available via CSI-2 serial data output (1 Lane).
> >> +
> >> +properties:
> >> + compatible:
> >> + const: sony,imx296
> >> +
> >> + reg:
> >> + maxItems: 1
> >> +
> >> + clocks:
> >> + maxItems: 1
> >> +
> >> + clock-names:
> >> + description:
> >> + Input clock for the sensor.
> >> + items:
> >> + - const: mclk
> >
> > The pin is named INCK, let's name the clock accordingly.
>
> Okay, I thought generic names are preferred here!
>
> >> + clock-frequency:
> >> + description:
> >> + Frequency of the mclk clock in Hertz.
> >
> > This shouldn't be needed, you can retrieve the clock frequency at
> > runtime from the clock source.
>
> Unless the clock source is a fixed one! What if the clock source comes from
> SoC? We need to set the rate, right?

In that case, if you want to hardcode the clock in DT, the preferred way
is to use the assigned-clock-rates property. Otherwise, if the driver
requires a specific clock frequency, it's better to hardcode it in the
driver itself. In this specific case, I think assigned-clock-rates is
best as the device can support three different clock frequencies.

> >> + vddo-supply:
> >> + description:
> >> + Definition of the regulator used as interface power supply.
> >> +
> >> + vdda-supply:
> >> + description:
> >> + Definition of the regulator used as analog power supply.
> >> +
> >> + vddd-supply:
> >> + description:
> >> + Definition of the regulator used as digital power supply.
> >
> > Do we really need three regulators ? I agree that the sensor has three
> > power rails, but aren't they usually powered by regulators that are
> > tied together, without individual control ? The IMX926 specifications
> > require the three power supplies to raise within 200ms, which we should
> > be able to ensure in software. What does your board use, does it have
> > multiple GPIOs to control each power supply ? If not I wonder if we
> > could just define vddd-supply now, and add vdda-supply and vddo-supply
> > later if we need to support systems that can control the supplies
> > individually.
>
> The whole power supply model is a bit rotten. In my case, there are 3 different
> regulators used with no software control. So, I can't control the rise time
> (I assume that they are handled by the external power regulator itself).
>
> So to be sane, I just documented with the assumption of fixed-regulators.

Should we then go for one supply, and add the other two when (and if)
needed ?

> >> + reset-gpios:
> >> + description:
> >> + The phandle and specifier for the GPIO that controls sensor reset.
> >> + maxItems: 1
> >> +
> >> + port: true
> >> +
> >> +required:
> >> + - compatible
> >> + - reg
> >> + - clocks
> >> + - clock-names
> >> + - clock-frequency
> >> + - vddo-supply
> >> + - vdda-supply
> >> + - vddd-supply
> >> +
> >> +additionalProperties: false
> >> +
> >> +examples:
> >> + - |
> >> + #include <dt-bindings/gpio/gpio.h>
> >> +
> >> + imx296: camera-sensor@1a {
> >> + compatible = "sony,imx296";
> >> + reg = <0x1a>;
> >> + reset-gpios = <&msmgpio 35 GPIO_ACTIVE_LOW>;
> >> + pinctrl-names = "default";
> >> + pinctrl-0 = <&camera_rear_default>;
> >> + clocks = <&gcc 90>;
> >> + clock-names = "mclk";
> >> + clock-frequency = <37125000>;
> >> + vddo-supply = <&camera_vddo_1v8>;
> >> + vdda-supply = <&camera_vdda_3v3>;
> >> + vddd-supply = <&camera_vddd_1v2>;
> >> +
> >> + port {
> >> + imx296_ep: endpoint {
> >> + remote-endpoint = <&csiphy0_ep>;
> >> + };
> >> + };
> >> + };
> >> +
> >> +...
> >> diff --git a/MAINTAINERS b/MAINTAINERS
> >> index 55199ef7fa74..51194bb2c392 100644
> >> --- a/MAINTAINERS
> >> +++ b/MAINTAINERS
> >> @@ -15140,6 +15140,14 @@ S: Maintained
> >> F: drivers/media/i2c/imx274.c
> >> F: Documentation/devicetree/bindings/media/i2c/imx274.txt
> >>
> >> +SONY IMX296 SENSOR DRIVER
> >> +M: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> >> +L: linux-media@vger.kernel.org
> >> +T: git git://linuxtv.org/media_tree.git
> >> +S: Maintained
> >> +F: drivers/media/i2c/imx296.c
> >> +F: Documentation/devicetree/bindings/media/i2c/imx296.yaml
> >> +
> >> SONY IMX319 SENSOR DRIVER
> >> M: Bingbu Cao <bingbu.cao@intel.com>
> >> L: linux-media@vger.kernel.org

--
Regards,

Laurent Pinchart