Re: [PATCH v2 1/2] [media] media: i2c/ov5645: add the device tree binding document

[Todor Tomov <todor.tomov@linaro.org>]

On 05/20/2016 03:16 AM, Rob Herring wrote:
> On Thu, May 19, 2016 at 3:14 AM, Todor Tomov <todor.tomov@linaro.org> wrote:
>> Hi Rob,
>>
>> Thank you for your time to review. My responses are below:
>>
>> On 05/19/2016 02:16 AM, Rob Herring wrote:
>>> On Wed, May 18, 2016 at 02:50:07PM +0300, Todor Tomov wrote:
>>>> Add the document for ov5645 device tree binding.
>>>>
>>>> Signed-off-by: Todor Tomov <todor.tomov@linaro.org>
>>>> ---
>>>>  .../devicetree/bindings/media/i2c/ov5645.txt       | 56 ++++++++++++++++++++++
>>>>  1 file changed, 56 insertions(+)
>>>>  create mode 100644 Documentation/devicetree/bindings/media/i2c/ov5645.txt
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/media/i2c/ov5645.txt b/Documentation/devicetree/bindings/media/i2c/ov5645.txt
>>>> new file mode 100644
>>>> index 0000000..8799000
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/media/i2c/ov5645.txt
>>>> @@ -0,0 +1,56 @@
>>>> +* Omnivision 1/4-Inch 5Mp CMOS Digital Image Sensor
>>>> +
>>>> +The Omnivision OV5645 is a 1/4-Inch CMOS active pixel digital image sensor with
>>>> +an active array size of 2592H x 1944V. It is programmable through a serial SCCB
>>>
>>> s/SCCB/I2C/ because that is the more common name.
>> Ok.
>>
>>>
>>>> +interface.
>>>> +
>>>> +Required Properties:
>>>> +- compatible: value should be "ovti,ov5645"
>>>> +- clocks: reference to the xclk clock
>>>> +- clock-names: should be "xclk"
>>>> +- assigned-clocks: reference to the xclk clock
>>>
>>> This should be optional as it only makes sense if there is more than one
>>> option.
>> I have only used assigned-clocks to specify for which clock the
>> assigned-clock-rates property is. This is the way I understood it.
>> Isn't this correct? (Also please see below.)
> 
> AIUI, assigned-clocks is which parent you want to assign for the clock
> specified in "clocks". Whether you have a parent option or not is
> board/chip dependent.
> 
>>>> +- assigned-clock-rates: should be "23880000"
>>>
>>> Doesn't this depend on the board? Most parts take a range of
>>> frequencies. The driver should know what the range is and request a rate
>>> within this range.
>> This is the sensor external clock. Actually the driver depends on this value -
>> the sensor mode settings which the driver configures are calculated based on
>> this value. If you change this clock rate you need to change the sensor mode
>> settings. However they usually come from the vendor of the sensor so they
>> usually never change. So this clock rate for this driver is fixed to 23.88MHz
>> and is not expected to change.
> 
> If fixed in the driver, then it doesn't need to be in DT.
Ok, I'll remove these two and leave the external clock value in the driver.

> 
>>>> +
>>>> +Optional Properties:
>>>> +- reset-gpios: Chip reset GPIO
>>>> +- pwdn-gpios: Chip power down GPIO
>>>
>>> Use enable-gpios as it is more common and would just be the inverse of
>>> this.
>> pwdn is the notation which OV use for this gpio, so I'd personally prefer
>> to keep the name. Do you think it is still better to change it?
> 
> Yes.
Ok, I'll change it to enable-gpios. Thanks.

> 
> Rob
> 

-- 
Best regards,
Todor Tomov