From: Robert Foss <robert.foss@linaro.org>
To: Maxime Ripard <maxime@cerno.tech>
Cc: Dongchun Zhu <dongchun.zhu@mediatek.com>,
Fabio Estevam <festevam@gmail.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Sakari Ailus <sakari.ailus@iki.fi>,
Tomasz Figa <tfiga@chromium.org>,
linux-media <linux-media@vger.kernel.org>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v6 1/3] media: dt-bindings: ov8856: Document YAML bindings
Date: Thu, 2 Apr 2020 12:10:00 +0200 [thread overview]
Message-ID: <CAG3jFyvUd08U9yNVPUD9Y=nd5Xpcx34GcHJRhtvAAycoq3qimg@mail.gmail.com> (raw)
In-Reply-To: <20200401080705.j4goeqcqhoswhx4u@gilmour.lan>
Hey Maxime,
On Wed, 1 Apr 2020 at 10:07, Maxime Ripard <maxime@cerno.tech> wrote:
>
> Hi,
>
> On Tue, Mar 31, 2020 at 03:33:44PM +0200, Robert Foss wrote:
> > From: Dongchun Zhu <dongchun.zhu@mediatek.com>
> >
> > This patch adds documentation of device tree in YAML schema for the
> > OV8856 CMOS image sensor.
> >
> > Signed-off-by: Dongchun Zhu <dongchun.zhu@mediatek.com>
> > Signed-off-by: Robert Foss <robert.foss@linaro.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@intel.com>
> > + - Dongchun Zhu <dongchun.zhu@mediatek.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.
>
> 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
next prev parent reply other threads:[~2020-04-02 10:10 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-31 13:33 [PATCH v3 0/3] media: ov8856: Add devicetree support Robert Foss
2020-03-31 13:33 ` [PATCH v6 1/3] media: dt-bindings: ov8856: Document YAML bindings Robert Foss
2020-03-31 15:12 ` Marco Felsch
2020-04-02 9:57 ` Robert Foss
2020-04-03 19:21 ` Marco Felsch
2020-04-01 8:07 ` Maxime Ripard
2020-04-02 10:10 ` Robert Foss [this message]
2020-04-03 23:27 ` Sakari Ailus
2020-04-04 9:34 ` Maxime Ripard
2020-04-06 8:25 ` Robert Foss
2020-04-06 8:35 ` Sakari Ailus
2020-04-07 8:36 ` Maxime Ripard
2020-04-07 11:29 ` Robert Foss
2020-04-07 12:32 ` Maxime Ripard
2020-04-07 15:47 ` Robert Foss
2020-04-07 16:39 ` Sakari Ailus
2020-04-07 16:46 ` Tomasz Figa
2020-04-07 17:20 ` Sakari Ailus
2020-04-08 12:21 ` Maxime Ripard
2020-04-08 12:35 ` Tomasz Figa
2020-04-08 13:43 ` Maxime Ripard
2020-04-08 15:28 ` Sakari Ailus
2020-04-08 15:30 ` Sakari Ailus
2020-04-08 16:34 ` Andy Shevchenko
2020-04-15 10:18 ` Maxime Ripard
2020-04-15 11:10 ` Robert Foss
2020-04-15 16:16 ` Sakari Ailus
2020-04-20 15:02 ` Maxime Ripard
2020-04-09 8:32 ` Robert Foss
2020-04-07 16:20 ` Sakari Ailus
2020-04-04 9:23 ` Maxime Ripard
2020-03-31 13:33 ` [PATCH v3 2/3] media: ov8856: Add devicetree support Robert Foss
2020-03-31 14:01 ` Andy Shevchenko
2020-04-06 13:37 ` Robert Foss
2020-04-06 15:06 ` Andy Shevchenko
2020-04-06 15:25 ` Robert Foss
2020-04-03 23:33 ` Sakari Ailus
2020-03-31 13:33 ` [PATCH v3 3/3] media: ov8856: Implement sensor module revision identification Robert Foss
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