Hey Maxime, On Wed, 1 Apr 2020 at 10:07, Maxime Ripard <maxime@xxxxxxxxxx> wrote: > > Hi, > > On Tue, Mar 31, 2020 at 03:33:44PM +0200, Robert Foss wrote: > > From: Dongchun Zhu <dongchun.zhu@xxxxxxxxxxxx> > > > > This patch adds documentation of device tree in YAML schema for the > > OV8856 CMOS image sensor. > > > > Signed-off-by: Dongchun Zhu <dongchun.zhu@xxxxxxxxxxxx> > > Signed-off-by: Robert Foss <robert.foss@xxxxxxxxxx> > > --- > > > > - 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@xxxxxxxxx> > > + - Dongchun Zhu <dongchun.zhu@xxxxxxxxxxxx> > > + > > +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. > > We also had that discussion recently for another omnivision sensor > (ov5645 iirc), but what is clock-frequency useful for? > > It seems that the sensor is passed in clocks, so if you need to > retrieve the clock rate you should use the clock API instead. > > Looking at the driver, it looks like it first retrieves the clock, set > it to clock-frequency, and then checks that this is OV8856_XVCLK_19_2 > (19.2 MHz). As far as I understand it, 19.2MHz is requirement for the sensor mode that currently defaults to. Some modes require higher clock speeds than this however. > > The datasheet says that the sensor can have any frequency in the 6 - > 27 MHz range, so this is a driver limitation and should be set in the > driver using the clock API, and you can always bail out if it doesn't > provide a rate that is not acceptable for the drivers assumption. > > In any case, you don't need clock-frequency here... So your suggestion is that we remove all clocks-rate properties, and replace the clk_get_rate() calls in the driver with clk_set_rate() calls for the desired frequencies? > > > + assigned-clocks: > > + description: > > + Input clock for the sensor. > > + > > + assigned-clock-rates: > > + description: > > + Frequency of the xvclk clock in Hertz. > > And you don't need assigned-clock-rates either. Ack. > > Maxime
