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Subject: Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver
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From:   Sowjanya Komatineni <skomatineni@nvidia.com>
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Date:   Tue, 7 Apr 2020 15:22:05 -0700
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On 4/7/20 3:08 PM, Dmitry Osipenko wrote:
> External email: Use caution opening links or attachments
>
>
> 08.04.2020 00:08, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
> ...
>>>> I think you need a semaphore with resource count =3D 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 >=3D SYNCPT_FIFO_DEPTH. So some change
> should be needed to prevent this.
>
> The wait_event_interruptible seems should be okay.

We don't want to prevent that as we already have buffers available for=20
capture so as soon as VI HW issuing single shot is done and when min 1=20
slot is empty we should continue with issuing for another capture.

As long as buffers are available, we should continue to capture and=20
should not hold