linux-kernel - Re: [PATCH v1 0/6] Add support of OV9655 camera

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Message-Id: <AA7BA0B2-F16F-4BEE-B2ED-7C452D7C4A6F@goldelico.com>
Date:   Mon, 26 Jun 2017 08:02:31 +0200
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Hugues Fruchet <hugues.fruchet@...com>
Cc:     Mark Rutland <mark.rutland@....com>,
        devicetree <devicetree@...r.kernel.org>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Alexandre Torgue <alexandre.torgue@...com>,
        LKML <linux-kernel@...r.kernel.org>,
        Hans Verkuil <hverkuil@...all.nl>,
        Rob Herring <robh+dt@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Yannick Fertre <yannick.fertre@...com>,
        Sylwester Nawrocki <sylvester.nawrocki@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Guennadi Liakhovetski <g.liakhovetski@....de>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-media@...r.kernel.org,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>
Subject: Re: [PATCH v1 0/6] Add support of OV9655 camera

Hi Hugues,

> Am 23.06.2017 um 12:25 schrieb H. Nikolaus Schaller <hns@...delico.com>:
> 
> Hi Hugues,
> 
>> Am 22.06.2017 um 17:41 schrieb H. Nikolaus Schaller <hns@...delico.com>:
>> 
>> 
>>> Am 22.06.2017 um 17:05 schrieb Hugues Fruchet <hugues.fruchet@...com>:
>>> 
>>> 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.
>>> 
>>> OV9655 initial support is based on a driver written by H. Nikolaus Schaller [1].
>> 
>> Great!
> 
> Thanks again for picking up or work and trying to get it upstream.
> 
>> 
>> I will test as soon as possible.

Here are some more test results and fixes:

> 
> I have tried and had to fix some issues first:
> * gpio properties have a different name than in our approach (but that is something maintainers have to decide and is easy to follow this or that way)
> * there is no clock-frequency property which makes the driver request a clock frequency (something our camera interface expects this way)

This can indeed be replaced by assigned-clock-rates and no additional
driver code. So there is no need to implement anything new here.

> * there is no vana-supply regulator and we need that to power on/off the camera on demand (reset and pwdn isn't enough in our hardware)

this is something we still need to have added by patch

<http://git.goldelico.com/?p=gta04-kernel.git;a=blobdiff;f=drivers/media/i2c/ov9650.c;h=ed5d0a53a9c72036d6e017094b68111b5eb7f00d;hp=c0819afdcefcb19da351741d51dad00aaf909254;hb=da8ae2b038a448c8f822b3a4f20ed378db6d2934;hpb=6db55fc472eea2ec6db03833df027aecf6649f88>

> * for some unknown reason the driver does not load automatically from DT compatibility string and needs to be explicitly modprobed

This turned out to be because the i2c device ids are upper case while compatible-strings
are lower-case. See comment for patch 6/6.

BR and looking forward to v2,
Nikolaus