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Date:   Mon, 1 Nov 2021 20:06:52 +0100
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Subject: Re: [PATCH 04/17] media: atomisp: pci: do not use err var when
 checking port validity for ISP2400
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To:     Mauro Carvalho Chehab <mchehab@kernel.org>,
        Tsuchiya Yuto <kitakar@gmail.com>
Cc:     Sakari Ailus <sakari.ailus@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-media@vger.kernel.org, linux-staging@lists.linux.dev,
        linux-kernel@vger.kernel.org,
        Nable <nable.maininbox@googlemail.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Fabio Aiuto <fabioaiuto83@gmail.com>,
        "andrey.i.trufanov" <andrey.i.trufanov@gmail.com>,
        Patrik Gfeller <patrik.gfeller@gmail.com>
References: <20211017161958.44351-1-kitakar@gmail.com>
 <20211017161958.44351-5-kitakar@gmail.com> <20211026092637.196447aa@sal.lan>
 <1a295721fd1f1e512cd54a659a250aef162bfb6f.camel@gmail.com>
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 <af7cdf9de020171567c2e75b713deb2ed073e4e3.camel@gmail.com>
 <20211101141058.36ea2c8e@sal.lan>
From:   Hans de Goede <hdegoede@redhat.com>
In-Reply-To: <20211101141058.36ea2c8e@sal.lan>
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Hi,

On 11/1/21 15:10, Mauro Carvalho Chehab wrote:

<snip>

>>> Did you test on Baytrail (ISP2400), and with the compile-time option
>>> enabled/disabled?  
>>
>> Sorry, I should have clarified on the cover later. For ISP2400, I did
>> compile test only (CONFIG_VIDEO_ATOMISP_ISP2401 enabled/disabled).
> 
> Maybe Hans could help us on that. I guess he has an Asus T100 device, 
> which is BYT based.
> 
> Hans, if you're willing to do the tests, you could either use nvt
> or v4l2grab to test it.
> 
> It seems that BYT has an additional issue, though: the ISP seems to
> require 12 non-visible lines/columns (in addition to 16 ones required
> by CHT?) for it to work.
> 
> So, you may need to tweak the resolution a bit, as otherwise the
> driver will return an -EINVAL.
> 
> See:
> 
> 	https://git.linuxtv.org/media_stage.git/commit/?id=dcbc4f570495dbd490975979471687cbe2246f99
> 
> For the workaround I had to add for CHT to properly report the
> visible resolution.

Testing BYT support definitely is on my radar. Note that BYT
also has the additional issue that the atomisp2 on BYT can be
enumerated as either a PCI dev (which may work) or an ACPI/platform
dev which is unsupported in the original atomisp2 code-drop and
seems non trivial (because of pci config space writes) to get to
work.

On the T100TA the device is actually enumerated as an ACPI/platform
device and the BIOS option to change this is hidden. In the mean
time I've gained quite a lot of experience with changing hidden
BIOS options though, so I can easily put it in PCI mode for
testing. But eventually we also need to tackle ACPI enumeration
support...

Anyways I've let me self get distracted (hobby time wise) by
looking into PMIC/charger/fuel-gauge issues on the Xiaomi Mi Pad 2.
I've made a list of 3 (small-ish) loose ends which I want to
tie up there and then I plan to start looking into atomisp2
support in my hobby time. ATM my plan is:

   -Test on T101HA to reproduce Mauro's work
   -Try to get things to work on the T116
   -Patch to not load atomisp_foo sensor drivers on !BYT && !CHT
   
And I've just added:

   -Try out BYT support 

As 4th item. Eventually I want to look into writing a proper
regulator driver for the PMICs and then try to make the atomisp2
code work with the non "atomisp_xxx" versions of the sensor drivers.

Regards,

Hans