linux-kernel - Re: [PATCH v2 0/7] Add support of OV9655 camera

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Message-ID: <8050f688-fc6e-c3c0-460a-93ad3ae8d735@st.com>
Date:   Thu, 20 Jul 2017 09:17:38 +0000
From:   Hugues FRUCHET <hugues.fruchet@...com>
To:     "H. Nikolaus Schaller" <hns@...delico.com>,
        Sakari Ailus <sakari.ailus@....fi>,
        Sylwester Nawrocki <snawrocki@...nel.org>,
        "Hans Verkuil" <hverkuil@...all.nl>
CC:     Guennadi Liakhovetski <g.liakhovetski@....de>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre TORGUE <alexandre.torgue@...com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        devicetree <devicetree@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Yannick FERTRE" <yannick.fertre@...com>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>
Subject: Re: [PATCH v2 0/7] Add support of OV9655 camera



On 07/20/2017 10:37 AM, H. Nikolaus Schaller wrote:
> Hi,
> 
>> Am 18.07.2017 um 21:52 schrieb Sakari Ailus <sakari.ailus@....fi>:
>>
>> On Tue, Jul 18, 2017 at 12:53:12PM +0000, Hugues FRUCHET wrote:
>>>
>>>
>>> On 07/18/2017 02:17 PM, H. Nikolaus Schaller wrote:
>>>> Hi,
>>>>
>>>>> Am 18.07.2017 um 13:59 schrieb Hans Verkuil <hverkuil@...all.nl>:
>>>>>
>>>>> On 12/07/17 22:01, Sylwester Nawrocki wrote:
>>>>>> Hi Hugues,
>>>>>>
>>>>>> On 07/03/2017 11:16 AM, Hugues Fruchet wrote:
>>>>>>> This patchset enables OV9655 camera support.
>>>>>>>
>>>>>>> OV9655 support has been tested using STM32F4DIS-CAM extension board
>>>>>>> plugged on connector P1 of STM32F746G-DISCO board.
>>>>>>> Due to lack of OV9650/52 hardware support, the modified related code
>>>>>>> could not have been checked for non-regression.
>>>>>>>
>>>>>>> First patches upgrade current support of OV9650/52 to prepare then
>>>>>>> introduction of OV9655 variant patch.
>>>>>>> Because of OV9655 register set slightly different from OV9650/9652,
>>>>>>> not all of the driver features are supported (controls). Supported
>>>>>>> resolutions are limited to VGA, QVGA, QQVGA.
>>>>>>> Supported format is limited to RGB565.
>>>>>>> Controls are limited to color bar test pattern for test purpose.
>>>>>>
>>>>>> I appreciate your efforts towards making a common driver but IMO it would be
>>>>>> better to create a separate driver for the OV9655 sensor.  The original driver
>>>>>> is 1576 lines of code, your patch set adds half of that (816).  There are
>>>>>> significant differences in the feature set of both sensors, there are
>>>>>> differences in the register layout.  I would go for a separate driver, we
>>>>>> would then have code easier to follow and wouldn't need to worry about possible
>>>>>> regressions.  I'm afraid I have lost the camera module and won't be able
>>>>>> to test the patch set against regressions.
>>>>>>
>>>>>> IMHO from maintenance POV it's better to make a separate driver. In the end
>>>>>> of the day we wouldn't be adding much more code than it is being done now.
>>>>>
>>>>> I agree. We do not have great experiences in the past with trying to support
>>>>> multiple variants in a single driver (unless the diffs are truly small).
>>>>
>>>> Well,
>>>> IMHO the diffs in ov965x are smaller (but untestable because nobody seems
>>>> to have an ov9650/52 board) than within the bq27xxx chips, but I can dig out
>>>> an old pdata based separate ov9655 driver and extend that to become DT compatible.
>>>>
>>>> I had abandoned that separate approach in favour of extending the ov965x driver.
>>>>
>>>> Have to discuss with Hugues how to proceed.
>>>>
>>>> BR and thanks,
>>>> Nikolaus
>>>>
>>>
>>> As Sylwester and Hans, I'm also in flavour of a separate driver, the
>>> fact that register set seems similar but in fact is not and that we
>>> cannot test for non-regression of 9650/52 are killer for me to continue
>>> on a single driver.
>>> We can now restart from a new fresh state of the art sensor driver
>>> getting rid of legacy (pdata, old gpio, etc...).
>>
>> Agreed. I bet the result will look cleaner indeed although this wasn't one
>> of the complex drivers.
> 
> I finally managed to find the bug why mplayer did select-timeout on the GTA04.
> Was a bug in pinmux setup of the GTA04 for the omap3isp.
> 
> And I have resurrected our years old 3.12 camera driver, which was based on the
> MT9P031 code. It was already separate from ov9650/52.
> 
> I have extended it to support DT by including some parts of Hugues' work.
> 
> It still needs some cleanup and discussion but will be a simple patch (one
> for ov9655.c + Kconfig + Makefile) and one for bindings (I hope it includes
> all your comments).
> 
> I will post v1 in the next days.
> 
> BR,
> Nikolaus
> 

Thanks Nikolaus,

I was ready to push the new version in new file ov9655.c with all 
comments included, but as my version is very minimal and I suspect that 
yours is more complete, let's merge things together.
Can I consider that you now take ownership of this driver upstream ?
If so I'll send to you my current patchset so you can compare, 
double-check review comments and add missing support on your side 
(RGB565 and VGA/QVGA resolution matter on my side).

Thanks again Nikolaus for this work,

BR,
Hugues.