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

Sowjanya Komatineni
2020-04-06T20:55:17Z

On 4/6/20 1:53 PM, Dmitry Osipenko wrote:
> External email: Use caution opening links or attachments
>
>
> 06.04.2020 23:50, Sowjanya Komatineni пишет:
>> 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 пишет:
>>>> +static int chan_capture_kthread_start(void *data)
>>>> +{
>>>> + struct tegra_vi_channel *chan = data;
>>>> + struct tegra_channel_buffer *buf;
>>>> + int err = 0;
>>>> + int caps_inflight;
>>>> +
>>>> + set_freezable();
>>>> +
>>>> + while (1) {
>>>> + try_to_freeze();
>>>> +
>>>> + wait_event_interruptible(chan->start_wait,
>>>> + !list_empty(&chan->capture) ||
>>>> + kthread_should_stop());
>>>> + /*
>>>> + * Frame start and MW_ACK_DONE syncpoint condition
>>>> FIFOs are
>>>> + * of max depth 2. So make sure max 2 capture requests are
>>>> + * in process by the hardware at a time.
>>>> + */
>>>> + while (!(kthread_should_stop() ||
>>>> list_empty(&chan->capture))) {
>>>> + caps_inflight = chan->capture_reqs -
>>>> chan->sequence;
>>>> + /*
>>>> + * Source is not streaming if error is non-zero.
>>>> + * So, do not dequeue buffers on capture error
>>>> or when
>>>> + * syncpoint requests in FIFO are full.
>>>> + */
>>>> + if (err || caps_inflight >= SYNCPT_FIFO_DEPTH)
>>>> + 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.
condition is checked when waitqueue is woken up