From: "Andreas Färber" <afaerber@suse.de>
To: "H. Nikolaus Schaller" <hns@goldelico.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
Hugues Fruchet <hugues.fruchet@st.com>,
Suman Anna <s-anna@ti.com>, Mark Rutland <mark.rutland@arm.com>,
devicetree <devicetree@vger.kernel.org>,
Benjamin Gaignard <benjamin.gaignard@linaro.org>,
Discussions about the Letux Kernel
<letux-kernel@openphoenux.org>,
Alexandre Torgue <alexandre.torgue@st.com>,
LKML <linux-kernel@vger.kernel.org>,
Hans Verkuil <hverkuil@xs4all.nl>,
Rob Herring <robh+dt@kernel.org>,
Maxime Coquelin <mcoquelin.stm32@gmail.com>,
Yannick Fertre <yannick.fertre@st.com>,
Sylwester Nawrocki <sylvester.nawrocki@gmail.com>,
Mauro Carvalho Chehab <mchehab@kernel.org>,
Guennadi Liakhovetski <g.liakhovetski@gmx.de>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
linux-media@vger.kernel.org
Subject: Re: [PATCH v1 1/6] DT bindings: add bindings for ov965x camera module
Date: Fri, 23 Jun 2017 16:57:19 +0200 [thread overview]
Message-ID: <88d0e8ea-74e4-6845-4e0d-8cd0f3a054be@suse.de> (raw)
In-Reply-To: <24C976BF-52FD-4509-BCE4-9AE41B335482@goldelico.com>
Am 23.06.2017 um 16:53 schrieb H. Nikolaus Schaller:
> Hi Laurent,
>
>> Am 23.06.2017 um 13:58 schrieb Laurent Pinchart <laurent.pinchart@ideasonboard.com>:
>>
>> Hi Nikolaus,
>>
>> On Friday 23 Jun 2017 12:59:24 H. Nikolaus Schaller wrote:
>>> Am 23.06.2017 um 12:46 schrieb Andreas Färber <afaerber@suse.de>:
>>>> Am 23.06.2017 um 12:25 schrieb H. Nikolaus Schaller:
>>>>>> diff --git a/Documentation/devicetree/bindings/media/i2c/ov965x.txt
>>>>>> b/Documentation/devicetree/bindings/media/i2c/ov965x.txt new file mode
>>>>>> 100644
>>>>>> index 0000000..0e0de1f
>>>>>> --- /dev/null
>>>>>> +++ b/Documentation/devicetree/bindings/media/i2c/ov965x.txt
>>>>>> @@ -0,0 +1,37 @@
>>>>>> +* Omnivision OV9650/9652/9655 CMOS sensor
>>>>>> +
>>>>>> +The Omnivision OV965x sensor support multiple resolutions output, such
>>>>>> as
>>>>>> +CIF, SVGA, UXGA. It also can support YUV422/420, RGB565/555 or raw RGB
>>>>>> +output format.
>>>>>> +
>>>>>> +Required Properties:
>>>>>> +- compatible: should be one of
>>>>>> + "ovti,ov9650"
>>>>>> + "ovti,ov9652"
>>>>>> + "ovti,ov9655"
>>>>>> +- clocks: reference to the mclk input clock.
>>>>>
>>>>> I wonder why you have removed the clock-frequency property?
>>>>>
>>>>> In some situations the camera driver must be able to tell the clock
>>>>> source which frequency it wants to see.
>>>>
>>>> That's what assigned-clock-rates property is for:
>>>>
>>>> https://www.kernel.org/doc/Documentation/devicetree/bindings/clock/clock-b
>>>> indings.txt
>>>>
>>>> AFAIU clock-frequency on devices is deprecated and equivalent to having
>>>> a clocks property pointing to a fixed-clock, which is different from a
>>>> clock with varying rate.
>>>
>>> I am not sure if that helps here. The OMAP3-ISP does not have a fixed clock
>>> rate so we can only have the driver define what it wants to see.
>>>
>>> And common practise for OMAP3-ISP based camera modules (e.g. N900, N9) is
>>> that they do it in the driver.
>>>
>>> Maybe ISP developers can comment?
>>
>> The OMAP3 ISP is a variable-frequency clock provider. The clock frequency is
>> controlled by the clock consumer. As such, it's up to the consumer to decide
>> whether to compute and request the clock rate dynamically at runtime, or use
>> the assigned-clock-rates property in DT.
>>
>> Some ISPs include a clock generator, others don't. It should make no
>> difference whether the clock is provided by the ISP, by a dedicated clock
>> source in the SoC or by a discrete on-board adjustable clock source.
>
> Thanks for explaining the background.
>
> Do you have an hint or example how to use the assigned-clock-rates property in
> a DT for a camera module connected to the omap3isp?
>
> Or does it just mean that it defines the property name?
Please read the documentation link I sent - it's in the very bottom and
should have an example.
Regards,
Andreas
--
SUSE Linux GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
next prev parent reply other threads:[~2017-06-23 14:57 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-22 15:05 [PATCH v1 0/6] Add support of OV9655 camera Hugues Fruchet
2017-06-22 15:05 ` [PATCH v1 1/6] DT bindings: add bindings for ov965x camera module Hugues Fruchet
2017-06-23 10:25 ` H. Nikolaus Schaller
2017-06-23 10:46 ` Andreas Färber
2017-06-23 10:59 ` H. Nikolaus Schaller
2017-06-23 11:58 ` Laurent Pinchart
2017-06-23 14:53 ` H. Nikolaus Schaller
2017-06-23 14:57 ` Andreas Färber [this message]
2017-06-23 15:22 ` H. Nikolaus Schaller
2017-06-23 18:05 ` Suman Anna
2017-06-23 18:59 ` H. Nikolaus Schaller
2017-06-23 22:24 ` Suman Anna
2017-06-26 6:00 ` H. Nikolaus Schaller
2017-06-26 10:35 ` Hugues FRUCHET
2017-06-26 20:04 ` Sylwester Nawrocki
2017-06-27 5:48 ` H. Nikolaus Schaller
2017-06-27 22:57 ` Sylwester Nawrocki
2017-06-28 9:12 ` H. Nikolaus Schaller
2017-06-28 10:50 ` Sylwester Nawrocki
2017-06-28 11:24 ` H. Nikolaus Schaller
2017-06-28 12:28 ` Hugues FRUCHET
2017-06-26 18:56 ` Rob Herring
2017-06-26 18:54 ` Rob Herring
2017-06-22 15:05 ` [PATCH v1 2/6] [media] ov9650: add device tree support Hugues Fruchet
2017-06-26 16:31 ` Sakari Ailus
2017-06-26 17:46 ` H. Nikolaus Schaller
2017-06-27 5:36 ` Sakari Ailus
2017-06-27 10:14 ` Hugues FRUCHET
2017-06-22 15:05 ` [PATCH v1 3/6] [media] ov9650: select the nearest higher resolution Hugues Fruchet
2017-06-22 15:05 ` [PATCH v1 4/6] [media] ov9650: use write_array() for resolution sequences Hugues Fruchet
2017-06-26 16:33 ` Sakari Ailus
2017-06-29 13:59 ` Hugues FRUCHET
2017-06-22 15:05 ` [PATCH v1 5/6] [media] ov9650: add multiple variant support Hugues Fruchet
2017-06-25 12:36 ` kbuild test robot
2017-06-22 15:05 ` [PATCH v1 6/6] [media] ov9650: add support of OV9655 variant Hugues Fruchet
2017-06-25 16:07 ` [PATCH] ov9650: fix semicolon.cocci warnings kbuild test robot
2017-06-25 16:07 ` [PATCH v1 6/6] [media] ov9650: add support of OV9655 variant kbuild test robot
2017-06-26 6:03 ` H. Nikolaus Schaller
2017-06-26 11:49 ` Hugues FRUCHET
2017-06-22 15:41 ` [PATCH v1 0/6] Add support of OV9655 camera H. Nikolaus Schaller
2017-06-23 10:25 ` H. Nikolaus Schaller
2017-06-25 9:18 ` omap3isp camera was " Pavel Machek
2017-06-26 6:05 ` H. Nikolaus Schaller
2017-06-26 8:39 ` Pavel Machek
2017-06-26 9:53 ` H. Nikolaus Schaller
2017-06-26 11:16 ` Pavel Machek
2017-06-27 5:49 ` H. Nikolaus Schaller
2017-06-26 13:19 ` Hugues FRUCHET
[not found] ` <E4E1E683-9CD0-4F23-AB03-080C52D0D73B@goldelico.com>
2017-06-27 7:57 ` Hugues FRUCHET
[not found] ` <95B10899-9966-4844-9667-D2434968A492@goldelico.com>
[not found] ` <85e62c47-e319-c801-376c-95f4d9cbf75a@st.com>
[not found] ` <E183E921-B8F4-4F8A-A302-58297A874990@goldelico.com>
[not found] ` <77bd3b8fe52643d68ecc821ec22bc0e6@SFHDAG5NODE1.st.com>
2017-07-01 21:00 ` H. Nikolaus Schaller
2017-07-03 8:16 ` Hugues FRUCHET
2017-07-03 9:14 ` H. Nikolaus Schaller
2017-07-03 12:03 ` Hugues FRUCHET
2017-07-03 12:23 ` H. Nikolaus Schaller
2017-07-05 14:02 ` H. Nikolaus Schaller
2017-07-08 20:55 ` Sakari Ailus
2017-06-26 6:02 ` H. Nikolaus Schaller
2017-06-26 10:05 ` Hugues FRUCHET
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