linux-kernel - Re: [PATCH 0/5] media: Allwinner A10 CSI support

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Message-ID: <cb504ffc-b74c-d6e3-7bde-6c5840c87997@cisco.com>
Date:   Tue, 13 Nov 2018 17:00:25 +0100
From:   Hans Verkuil <hansverk@...co.com>
To:     Maxime Ripard <maxime.ripard@...tlin.com>
Cc:     Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Hans Verkuil <hverkuil@...all.nl>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        linux-media@...r.kernel.org, Andrzej Hajda <a.hajda@...sung.com>,
        Chen-Yu Tsai <wens@...e.org>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>
Subject: Re: [PATCH 0/5] media: Allwinner A10 CSI support

On 11/13/18 16:52, Maxime Ripard wrote:
> On Tue, Nov 13, 2018 at 03:01:45PM +0100, Hans Verkuil wrote:
>> On 11/13/18 14:52, Maxime Ripard wrote:
>>> Hi Hans,
>>>
>>> On Tue, Nov 13, 2018 at 01:30:49PM +0100, Hans Verkuil wrote:
>>>> On 11/13/18 09:24, Maxime Ripard wrote:
>>>>> Hi,
>>>>>
>>>>> Here is a series introducing the support for the A10 (and SoCs of the same
>>>>> generation) CMOS Sensor Interface (called CSI, not to be confused with
>>>>> MIPI-CSI, which isn't support by that IP).
>>>>>
>>>>> That interface is pretty straightforward, but the driver has a few issues
>>>>> that I wanted to bring up:
>>>>>
>>>>>   * The only board I've been testing this with has an ov5640 sensor
>>>>>     attached, which doesn't work with the upstream driver. Copying the
>>>>>     Allwinner init sequence works though, and this is how it has been
>>>>>     tested. Testing with a second sensor would allow to see if it's an
>>>>>     issue on the CSI side or the sensor side.
>>>>>   * When starting a capture, the last buffer to capture will fail due to
>>>>>     double buffering being used, and we don't have a next buffer for the
>>>>>     last frame. I'm not sure how to deal with that though. It seems like
>>>>>     some drivers use a scratch buffer in such a case, some don't care, so
>>>>>     I'm not sure which solution should be preferred.
>>>>>   * We don't have support for the ISP at the moment, but this can be added
>>>>>     eventually.
>>>>>
>>>>>   * How to model the CSI module clock isn't really clear to me. It looks
>>>>>     like it goes through the CSI controller and then is muxed to one of the
>>>>>     CSI pin so that it can clock the sensor. I'm not quite sure how to
>>>>>     model it, if it should be a clock, the CSI driver being a clock
>>>>>     provider, or if the sensor should just use the module clock directly.
>>>>>
>>>>> Here is the v4l2-compliance output:
>>>>
>>>> Test v4l2-compliance with the -s option so you test streaming as well.
>>>> Even better is -f where it tests streaming with all available formats.
>>>
>>> I will, thanks for the tip!
>>>
>>>>> v4l2-compliance SHA   : 339d550e92ac15de8668f32d66d16f198137006c
>>>>
>>>> Hmm, I can't find this SHA. Was this built from the main v4l-utils repo?
>>>
>>> It was, but using Buildroot. The version packaged in the latest stable
>>> version I was using (2018.08) is 1.14.2.
>>
>> That's seriously out of date. That's why I show the SHA, to see if
>> someone is testing with a recent version of the utility, so it served
>> its purpose here :-)
>>
>> Latest release is 1.16.2.
>>
>> But when submitting new drivers you really need to build it yourself from
>> the master branch, that's the only way to be sure you have all the latest
>> compliance checks.
> 
> Ack, I'll update it and test again then.
> 
>>>
>>> Looking at the Makefile from v4l2-compliance, it looks like it just
>>> invokes git to retrieve the git commit and uses that as the hash. In
>>> Buildroot's case, since buildroot will download the tarball, this will
>>> end up returning the SHA commit of the buildroot repo building the
>>> sources, not the version of the sources themselves.
>>>
>>> I'm not sure how to address that properly though. Thomas, how do you
>>> usually deal with this?
>>
>> Note that cec-compliance and cec-follower do the same, for the same
>> reason.
>>
>> Where does the tarball come from?
> 
> This is the official tarball from linuxtv:
> https://git.buildroot.net/buildroot/tree/package/libv4l/libv4l.mk?h=2018.08.2#n8

Weird, if I build directly from that tarball, then v4l2-compliance should say:

v4l2-compliance SHA: not available, 64 bits

So that's what I expect to see from buildroot as well.

Regards,

	Hans