linux-kernel - Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver

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Message-ID: <0227d65f-283a-1488-a48c-7bab600eae35@nvidia.com>
Date:   Mon, 6 Apr 2020 13:30:54 -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>, <helen.koike@...labora.com>
CC:     <sboyd@...nel.org>, <linux-media@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-clk@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver


On 4/6/20 1:28 PM, Dmitry Osipenko wrote:
> External email: Use caution opening links or attachments
>
>
> 06.04.2020 23:05, Sowjanya Komatineni пишет:
> ..
>>>> Wait time for HW syncpt to reach threshold is tuned to work for all
>>>> frame rates. So if increment doesn't happen by then, its definitely
>>>> missed event.
>>> This is questionable. Technically, speculating about whether the tuned
>>> value is good for all possible cases is incorrect thing to do.
>>>
>>> Although, I guess in practice it should be good enough for the starter
>>> and could be improved later on, once the host1x driver will be improved.
>> By tuned value I meant about 200ms wait timeout for frame event to
>> happen is what we have been using in downstream and with BSP release
>> images which works good for all sensors and bridges we supported so far.
> I don't know anything about the state of today's downstream, but
> downstream of older Tegra SoCs was pretty awful in regards to the host1x
> syncing, unfortunately it was borrowed into the upstream host1x years
> ago and nothing was done about it so far. I'd suggest to be careful
> about it.
200ms timeout we wait for event to happen is the case even with 
T186/T194 as well and internally it was tuned from lots of testing with 
various sensors and frame rate computations which is known to work good.