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Date: Thu, 2 Apr 2020 11:57:10 +0200
From: Robert Foss <robert.foss@...aro.org>
To: Marco Felsch <m.felsch@...gutronix.de>
Cc: Dongchun Zhu <dongchun.zhu@...iatek.com>,
Fabio Estevam <festevam@...il.com>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Sakari Ailus <sakari.ailus@....fi>,
Tomasz Figa <tfiga@...omium.org>,
linux-media <linux-media@...r.kernel.org>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@...r.kernel.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE"
<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v6 1/3] media: dt-bindings: ov8856: Document YAML bindings
'Hey Marco,
On Tue, 31 Mar 2020 at 17:13, Marco Felsch <m.felsch@...gutronix.de> wrote:
>
> Hi Robert,
>
> On 20-03-31 15:33, Robert Foss wrote:
> > From: Dongchun Zhu <dongchun.zhu@...iatek.com>
> >
> > This patch adds documentation of device tree in YAML schema for the
> > OV8856 CMOS image sensor.
> >
> > Signed-off-by: Dongchun Zhu <dongchun.zhu@...iatek.com>
> > Signed-off-by: Robert Foss <robert.foss@...aro.org>
> > ---
> >
> > - Changes since v5:
> > * Add assigned-clocks and assigned-clock-rates
> > * robher: dt-schema errors
> >
> > - Changes since v4:
> > * Fabio: Change reset-gpio to GPIO_ACTIVE_LOW, explain in description
> > * Add clock-lanes property to example
> > * robher: Fix syntax error in devicetree example
> >
> > - Changes since v3:
> > * robher: Fix syntax error
> > * robher: Removed maxItems
> > * Fixes yaml 'make dt-binding-check' errors
> >
> > - Changes since v2:
> > Fixes comments from from Andy, Tomasz, Sakari, Rob.
> > * Convert text documentation to YAML schema.
> >
> > - Changes since v1:
> > Fixes comments from Sakari, Tomasz
> > * Add clock-frequency and link-frequencies in DT
> >
> > .../devicetree/bindings/media/i2c/ov8856.yaml | 150 ++++++++++++++++++
> > MAINTAINERS | 1 +
> > 2 files changed, 151 insertions(+)
> > create mode 100644 Documentation/devicetree/bindings/media/i2c/ov8856.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/media/i2c/ov8856.yaml b/Documentation/devicetree/bindings/media/i2c/ov8856.yaml
> > new file mode 100644
> > index 000000000000..beeddfbb8709
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/media/i2c/ov8856.yaml
> > @@ -0,0 +1,150 @@
> > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > +# Copyright (c) 2019 MediaTek Inc.
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/media/i2c/ov8856.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Omnivision OV8856 CMOS Sensor Device Tree Bindings
> > +
> > +maintainers:
> > + - Ben Kao <ben.kao@...el.com>
> > + - Dongchun Zhu <dongchun.zhu@...iatek.com>
> > +
> > +description: |-
> > + The Omnivision OV8856 is a high performance, 1/4-inch, 8 megapixel, CMOS
> > + image sensor that delivers 3264x2448 at 30fps. It provides full-frame,
> > + sub-sampled, and windowed 10-bit MIPI images in various formats via the
> > + Serial Camera Control Bus (SCCB) interface. This chip is programmable
> > + through I2C and two-wire SCCB. The sensor output is available via CSI-2
> > + serial data output (up to 4-lane).
> > +
> > +properties:
> > + compatible:
> > + const: ovti,ov8856
> > +
> > + reg:
> > + maxItems: 1
> > +
> > + clocks:
> > + maxItems: 1
> > +
> > + clock-names:
> > + description:
> > + Input clock for the sensor.
> > + items:
> > + - const: xvclk
> > +
> > + clock-frequency:
> > + description:
> > + Frequency of the xvclk clock in Hertz.
>
> Why do we need this here?
>
> > + assigned-clocks:
> > + description:
> > + Input clock for the sensor.
> > +
> > + assigned-clock-rates:
> > + description:
> > + Frequency of the xvclk clock in Hertz.
>
> Also this isn't related to the chip. You need this because you are using
> a qcom platform which provides the clock.
>
> IMHO you only need to specify the clock. You can get the frequency with
> the clk_get_rate() function.
The way I understood this, was that clk_get_rate() would fetch the
clock rate as defined by the 'assigned-clock-rates'
Is this not the case? And if so, what rate would cllk_get_rate()
actually retrieve?
>
> > + dovdd-supply:
> > + description:
> > + Definition of the regulator used as interface power supply.
>
> Phandle to the interface power supply regulator?
>
> > +
> > + avdd-supply:
> > + description:
> > + Definition of the regulator used as analog power supply.
> > +
> > + dvdd-supply:
> > + description:
> > + Definition of the regulator used as digital power supply.
> > +
> > + reset-gpios:
> > + description:
> > + The phandle and specifier for the GPIO that controls sensor reset.
> > + This corresponds to the hardware pin XSHUTDOWN which is physically
> > + active low.
> > +
> > + port:
> > + type: object
> > + additionalProperties: false
> > + description:
> > + A node containing input and output port nodes with endpoint definitions
> > + as documented in
> > + Documentation/devicetree/bindings/media/video-interfaces.txt
> > +
> > + properties:
> > + endpoint:
> > + type: object
> > +
> > + properties:
> > + clock-lanes:
> > + maxItems: 1
> > +
> > + data-lanes:
> > + maxItems: 1
> > +
> > + remote-endpoint: true
> > +
> > + required:
> > + - clock-lanes
> > + - data-lanes
> > + - remote-endpoint
> > +
> > + required:
> > + - endpoint
> > +
> > +required:
> > + - compatible
> > + - reg
> > + - clocks
> > + - clock-names
> > + - clock-frequency
> > + - assigned-clocks
> > + - assigned-clock-rates
> > + - dovdd-supply
> > + - avdd-supply
> > + - dvdd-supply
> > + - reset-gpios
> > + - port
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > + - |
> > + #include <dt-bindings/gpio/gpio.h>
> > + #include <dt-bindings/clock/qcom,camcc-sdm845.h>
>
> IMHO we should avoid examples with hardware specific includes.
The HW specific include is used for the clocks property.
clocks = <&clock_camcc CAM_CC_MCLK0_CLK>;
Is there a non hw specific clock that would be better to use for examples?
>
> > +
> > + i2c {
> > + #address-cells = <1>;
> > + #size-cells = <0>;
> > +
> > + ov8856: camera@10 {
> > + compatible = "ovti,ov8856";
> > + reg = <0x10>;
> > +
> > + reset-gpios = <&pio 111 GPIO_ACTIVE_LOW>;
> > + pinctrl-names = "default";
> > + pinctrl-0 = <&clk_24m_cam>;
> > +
> > + clocks = <&clock_camcc CAM_CC_MCLK0_CLK>;
> > + clock-names = "xvclk";
> > + clock-frequency = <19200000>;
> > + assigned-clocks = <&clock_camcc CAM_CC_MCLK0_CLK>;
> > + assigned-clock-rates = <19200000>;
> > +
> > + avdd-supply = <&mt6358_vcama2_reg>;
> > + dvdd-supply = <&mt6358_vcamd_reg>;
> > + dovdd-supply = <&mt6358_vcamio_reg>;
> > +
> > + port {
> > + wcam_out: endpoint {
> > + remote-endpoint = <&mipi_in_wcam>;
> > + clock-lanes = <0>;
> > + data-lanes = <1 2 3 4>;
> > + link-frequencies = /bits/ 64 <360000000 180000000>;
>
> Should we add the link-frequencies as optional param?
>
> Regards,
> Marco
>
> > + };
> > + };
> > + };
> > + };
> > +...
> > \ No newline at end of file
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index a6fbdf354d34..0f99e863978a 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -12355,6 +12355,7 @@ L: linux-media@...r.kernel.org
> > T: git git://linuxtv.org/media_tree.git
> > S: Maintained
> > F: drivers/media/i2c/ov8856.c
> > +F: Documentation/devicetree/bindings/media/i2c/ov8856.yaml
> >
> > OMNIVISION OV9650 SENSOR DRIVER
> > M: Sakari Ailus <sakari.ailus@...ux.intel.com>
> > --
> > 2.25.1
> >
> >
>
> --
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