Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver
From: Sowjanya Komatineni
Date: Tue Apr 07 2020 - 19:38:16 EST
On 4/7/20 4:36 PM, Sowjanya Komatineni wrote:
On 4/7/20 4:12 PM, Dmitry Osipenko wrote:
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08.04.2020 01:22, Sowjanya Komatineni ÐÐÑÐÑ:
On 4/7/20 3:08 PM, Dmitry Osipenko wrote:
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08.04.2020 00:08, Sowjanya Komatineni ÐÐÑÐÑ:
...
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.
The wait_event_interruptible seems should be okay.
We don't want to prevent that as we already have buffers available for
capture so as soon as VI HW issuing single shot is done and when min 1
slot is empty we should continue with issuing for another capture.
As long as buffers are available, we should continue to capture and
should not hold
I suppose that taking a shot takes at least few milliseconds, which
should be unacceptable to waste.
As long as buffers are in queue we have to keep processing each buffer
and between buffers obviously we have to wait for previous frames to
finish and this why we have separate thread for frame finish where we
can have next buffer capture ready and issue while previous frame
memory write happens