linux-kernel - Re: [RFC PATCH v5 13/14] media: tegra-video: Add CSI MIPI pads calibration

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Date:   Wed, 29 Jul 2020 16:59:52 -0700
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <frankc@...dia.com>, <hverkuil@...all.nl>,
        <sakari.ailus@....fi>, <robh+dt@...nel.org>,
        <helen.koike@...labora.com>
CC:     <sboyd@...nel.org>, <gregkh@...uxfoundation.org>,
        <linux-media@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-i2c@...r.kernel.org>
Subject: Re: [RFC PATCH v5 13/14] media: tegra-video: Add CSI MIPI pads
 calibration


On 7/29/20 4:25 PM, Dmitry Osipenko wrote:
> 28.07.2020 18:59, Sowjanya Komatineni пишет:
> ...
>>>> +        ret = tegra_mipi_finish_calibration(csi_chan->mipi);
>>>> +        if (ret < 0)
>>>> +            dev_err(csi_chan->csi->dev,
>>>> +                "MIPI calibration failed: %d\n", ret);
>>> Doesn't v4l2_subdev_call(OFF) need to be invoked here on error?
>> Not required as on error streaming fails and runtime PM will turn off
>> power anyway.
> I see that camera drivers bump theirs RPM on s_stream=1, and thus,
> s_stream=0 should be invoked in order to balance the RPM. What am I missing?
>
> https://elixir.bootlin.com/linux/v5.8-rc4/source/drivers/media/i2c/ov2740.c#L634

Sensor drivers take care of RPM put when any failure happens during 
s_stream.

So bridge driver don't have to call v4l2_subdev_call s_stream off incase 
if sensor subdev stream on fails.

>> Also we only did csi subdev s_stream on and during sensor subdev
>> s_stream on fail, actual stream dont happen and on tegra side frame
>> capture by HW happens only when kthreads run.
> Secondly, perhaps a failed calibration isn't a very critical error?
> Hence just printing a warning message should be enough.

Using dev_err to report calibration failure. Are you suggesting to use 
dev_warn instead of dev_err?

>
> Could you please make a patch that factors all ON/OFF code paths into a
> separate functions? It's a bit difficult to follow the combined code,
> especially partial changes in the patches. Thanks in advance!

what do you mean by partial changes in patches?

Can you please be more clear?

Thanks

Sowjanya