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

[Dmitry Osipenko]

06.04.2020 23:50, Sowjanya Komatineni ÐÐÑÐÑ:
> 
> On 4/6/20 1:45 PM, Dmitry Osipenko wrote:
>> External email: Use caution opening links or attachments
>>
>>
>> 04.04.2020 04:25, Sowjanya Komatineni ÐÐÑÐÑ:
>>> +static int chan_capture_kthread_start(void *data)
>>> +{
>>> +ÂÂÂÂ struct tegra_vi_channel *chan = data;
>>> +ÂÂÂÂ struct tegra_channel_buffer *buf;
>>> +ÂÂÂÂ int err = 0;
>>> +ÂÂÂÂ int caps_inflight;
>>> +
>>> +ÂÂÂÂ set_freezable();
>>> +
>>> +ÂÂÂÂ while (1) {
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂ try_to_freeze();
>>> +
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂ wait_event_interruptible(chan->start_wait,
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ !list_empty(&chan->capture) ||
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ kthread_should_stop());
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂ /*
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂ * Frame start and MW_ACK_DONE syncpoint condition
>>> FIFOs are
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂ * of max depth 2. So make sure max 2 capture requests are
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂ * in process by the hardware at a time.
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂ */
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂ while (!(kthread_should_stop() ||
>>> list_empty(&chan->capture))) {
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ caps_inflight = chan->capture_reqs -
>>> chan->sequence;
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ /*
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ * Source is not streaming if error is non-zero.
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ * So, do not dequeue buffers on capture error
>>> or when
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ * syncpoint requests in FIFO are full.
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ */
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ if (err || caps_inflight >= SYNCPT_FIFO_DEPTH)
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ break;
>> Am I understanding correctly that this thread will take 100% CPU,
>> spinning here, if more than 2 frame-captures queued?
> on more than 2 frames captures, it breaks thread and on next wakeup it
> continues

The wait_event() won't wait if condition is true.