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[91.78.208.152]) by smtp.googlemail.com with ESMTPSA id 22sm10489766ljq.69.2020.04.06.13.02.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 06 Apr 2020 13:02:42 -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> From: Dmitry Osipenko Message-ID: <782c8c4e-f5c2-d75e-0410-757172dd3090@gmail.com> Date: Mon, 6 Apr 2020 23:02:40 +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: <1585963507-12610-7-git-send-email-skomatineni@nvidia.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org 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()); Is it really okay that list_empty() isn't protected with a lock? Why wait_event is "interruptible"? > + /* > + * 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; > + > + /* dequeue the buffer and start capture */ > + spin_lock(&chan->start_lock); > + if (list_empty(&chan->capture)) > + break; > + buf = list_entry(chan->capture.next, > + struct tegra_channel_buffer, queue); list_first_entry() > + list_del_init(&buf->queue); > + spin_unlock(&chan->start_lock); > + > + err = tegra_channel_capture_frame(chan, buf); > + if (err) > + vb2_queue_error(&chan->queue); > + } > + > + if (kthread_should_stop()) > + break; > + } > + > + return 0; > +}