From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steve Longerbeam Subject: Re: [PATCH v5 15/39] [media] v4l2: add a frame interval error event Date: Sat, 11 Mar 2017 11:00:53 -0800 Message-ID: <1d3b4d81-587f-38c1-753f-4e7775dd4bca@gmail.com> References: <1489121599-23206-1-git-send-email-steve_longerbeam@mentor.com> <1489121599-23206-16-git-send-email-steve_longerbeam@mentor.com> <5b0a0e76-2524-4140-5ccc-380a8f949cfa@xs4all.nl> <6b574476-77df-0e25-a4d1-32d4fe0aec12@xs4all.nl> <5d5cf4a4-a4d3-586e-cd16-54f543dfcce9@gmail.com> <20170311185137.GE21222@n2100.armlinux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20170311185137.GE21222@n2100.armlinux.org.uk> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: driverdev-devel-bounces@linuxdriverproject.org Sender: "devel" To: Russell King - ARM Linux Cc: mark.rutland@arm.com, andrew-ct.chen@mediatek.com, minghsiu.tsai@mediatek.com, sakari.ailus@linux.intel.com, nick@shmanahar.org, songjun.wu@microchip.com, Hans Verkuil , pavel@ucw.cz, robert.jarzmik@free.fr, devel@driverdev.osuosl.org, markus.heiser@darmarIT.de, laurent.pinchart+renesas@ideasonboard.com, shuah@kernel.org, geert@linux-m68k.org, linux-media@vger.kernel.org, devicetree@vger.kernel.org, kernel@pengutronix.de, arnd@arndb.de, mchehab@kernel.org, bparrot@ti.com, robh+dt@kernel.org, horms+renesas@verge.net.au, tiffany.lin@mediatek.com, linux-arm-kernel@lists.infradead.org, niklas.soderlund+renesas@ragnatech.se, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, jean-christophe.trotin@st.com, p.zabel@pengutronix.de, fabio.estevam@nxp.com, shawnguo@kernel.org, sudipm.mukherjee@gmail.com List-Id: devicetree@vger.kernel.org On 03/11/2017 10:51 AM, Russell King - ARM Linux wrote: > On Sat, Mar 11, 2017 at 10:14:49AM -0800, Steve Longerbeam wrote: >> On 03/11/2017 03:39 AM, Hans Verkuil wrote: >>> It's fine to use an internal event as long as the end-user doesn't >>> see it. But if you lose vsyncs, then you never capture another frame, >>> right? >> >> No, that's not correct. By loss of vertical sync, I mean the IPU >> captures portions of two different frames, resulting in a permanent >> "split image", with one frame containing portions of two consecutive >> images. Or, the video rolls continuously, if you remember the old CRT >> television sets of yore, it's the same rolling effect. > > I have seen that rolling effect, but the iMX6 regains correct sync > within one complete "roll" just fine here with IMX219. However, it > has always recovered. > > So, I don't think there's a problem with the iMX6 part of the > processing, and so I don't think we should cripple the iMX6 capture > drivers for this problem. And there is no crippling going on. Measuring the frame intervals adds very little overhead. Steve