From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Osipenko Subject: Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver Date: Mon, 6 Apr 2020 23:56:28 +0300 Message-ID: <12a834ac-52b1-6dc0-7d3a-3e6a1fa85a2a@gmail.com> References: <1585963507-12610-1-git-send-email-skomatineni@nvidia.com> <1585963507-12610-7-git-send-email-skomatineni@nvidia.com> <200bb96e-2d07-764f-9e14-55538dc742fd@gmail.com> <23bfab09-b464-6e51-9843-06d13000e9b9@nvidia.com> <08cd31d5-e8b9-4d3a-fb0e-0e4462947d96@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <08cd31d5-e8b9-4d3a-fb0e-0e4462947d96-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> Content-Language: en-US Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Sowjanya Komatineni , thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org, frankc-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org, hverkuil-qWit8jRvyhVmR6Xm/wNWPw@public.gmane.org, sakari.ailus-X3B1VOXEql0@public.gmane.org, helen.koike-ZGY8ohtN/8qB+jHODAdFcQ@public.gmane.org Cc: sboyd-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, linux-media-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-clk-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-tegra@vger.kernel.org 06.04.2020 23:55, Sowjanya Komatineni пишет: > > 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 https://elixir.bootlin.com/linux/v5.6.2/source/include/linux/wait.h#L462