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

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Message-ID: <ee4cce05-2c60-6de1-2639-fe54abbf8345@gmail.com>
Date:   Wed, 8 Apr 2020 01:14:05 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.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

08.04.2020 01:08, Dmitry Osipenko пишет:
> 08.04.2020 00:08, Sowjanya Komatineni пишет:
> ...
>>>> I think you need a semaphore with resource count = 2.
>>> we hold on to issuing capture if more than 2 buffers are queued and it
>>> continues only after fifo has min 1 slot empty
>>
>>
>> Just want to close on this part of feedback. Hope above explanation is
>> clear regarding triggering/issuing at max 2 frame capture to VI HW and
>> also regarding capture threads where they use wait_event_interruptible
>> to prevent blocking waiting for buffers to be available for captures.
>>
>> So no changes related to this part are needed in v7.
> From what I see in the code, you "hold on" by making kthread to spin in
> a busy-loop while caps_inflight >= SYNCPT_FIFO_DEPTH. So some change
> should be needed to prevent this.

Looks like some other media drivers do:

	schedule_timeout_uninterruptible(1);

to avoid CPU hogging when contention is detected.