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[91.78.208.152]) by smtp.googlemail.com with ESMTPSA id n17sm10795873ljc.76.2020.04.06.13.53.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 06 Apr 2020 13:53:33 -0700 (PDT) Subject: Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver To: Sowjanya Komatineni , thierry.reding@gmail.com, jonathanh@nvidia.com, frankc@nvidia.com, hverkuil@xs4all.nl, sakari.ailus@iki.fi, helen.koike@collabora.com Cc: sboyd@kernel.org, linux-media@vger.kernel.org, devicetree@vger.kernel.org, linux-clk@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org 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> From: Dmitry Osipenko Message-ID: Date: Mon, 6 Apr 2020 23:53:31 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <23bfab09-b464-6e51-9843-06d13000e9b9@nvidia.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.