1*4882a593Smuzhiyun.. SPDX-License-Identifier: GPL-2.0 2*4882a593Smuzhiyun 3*4882a593Smuzhiyun========================= 4*4882a593Smuzhiyuni.MX Video Capture Driver 5*4882a593Smuzhiyun========================= 6*4882a593Smuzhiyun 7*4882a593SmuzhiyunEvents 8*4882a593Smuzhiyun====== 9*4882a593Smuzhiyun 10*4882a593Smuzhiyun.. _imx_api_ipuX_csiY: 11*4882a593Smuzhiyun 12*4882a593SmuzhiyunipuX_csiY 13*4882a593Smuzhiyun--------- 14*4882a593Smuzhiyun 15*4882a593SmuzhiyunThis subdev can generate the following event when enabling the second 16*4882a593SmuzhiyunIDMAC source pad: 17*4882a593Smuzhiyun 18*4882a593Smuzhiyun- V4L2_EVENT_IMX_FRAME_INTERVAL_ERROR 19*4882a593Smuzhiyun 20*4882a593SmuzhiyunThe user application can subscribe to this event from the ipuX_csiY 21*4882a593Smuzhiyunsubdev node. This event is generated by the Frame Interval Monitor 22*4882a593Smuzhiyun(see below for more on the FIM). 23*4882a593Smuzhiyun 24*4882a593SmuzhiyunControls 25*4882a593Smuzhiyun======== 26*4882a593Smuzhiyun 27*4882a593Smuzhiyun.. _imx_api_FIM: 28*4882a593Smuzhiyun 29*4882a593SmuzhiyunFrame Interval Monitor in ipuX_csiY 30*4882a593Smuzhiyun----------------------------------- 31*4882a593Smuzhiyun 32*4882a593SmuzhiyunThe adv718x decoders can occasionally send corrupt fields during 33*4882a593SmuzhiyunNTSC/PAL signal re-sync (too little or too many video lines). When 34*4882a593Smuzhiyunthis happens, the IPU triggers a mechanism to re-establish vertical 35*4882a593Smuzhiyunsync by adding 1 dummy line every frame, which causes a rolling effect 36*4882a593Smuzhiyunfrom image to image, and can last a long time before a stable image is 37*4882a593Smuzhiyunrecovered. Or sometimes the mechanism doesn't work at all, causing a 38*4882a593Smuzhiyunpermanent split image (one frame contains lines from two consecutive 39*4882a593Smuzhiyuncaptured images). 40*4882a593Smuzhiyun 41*4882a593SmuzhiyunFrom experiment it was found that during image rolling, the frame 42*4882a593Smuzhiyunintervals (elapsed time between two EOF's) drop below the nominal 43*4882a593Smuzhiyunvalue for the current standard, by about one frame time (60 usec), 44*4882a593Smuzhiyunand remain at that value until rolling stops. 45*4882a593Smuzhiyun 46*4882a593SmuzhiyunWhile the reason for this observation isn't known (the IPU dummy 47*4882a593Smuzhiyunline mechanism should show an increase in the intervals by 1 line 48*4882a593Smuzhiyuntime every frame, not a fixed value), we can use it to detect the 49*4882a593Smuzhiyuncorrupt fields using a frame interval monitor. If the FIM detects a 50*4882a593Smuzhiyunbad frame interval, the ipuX_csiY subdev will send the event 51*4882a593SmuzhiyunV4L2_EVENT_IMX_FRAME_INTERVAL_ERROR. Userland can register with 52*4882a593Smuzhiyunthe FIM event notification on the ipuX_csiY subdev device node. 53*4882a593SmuzhiyunUserland can issue a streaming restart when this event is received 54*4882a593Smuzhiyunto correct the rolling/split image. 55*4882a593Smuzhiyun 56*4882a593SmuzhiyunThe ipuX_csiY subdev includes custom controls to tweak some dials for 57*4882a593SmuzhiyunFIM. If one of these controls is changed during streaming, the FIM will 58*4882a593Smuzhiyunbe reset and will continue at the new settings. 59*4882a593Smuzhiyun 60*4882a593Smuzhiyun- V4L2_CID_IMX_FIM_ENABLE 61*4882a593Smuzhiyun 62*4882a593SmuzhiyunEnable/disable the FIM. 63*4882a593Smuzhiyun 64*4882a593Smuzhiyun- V4L2_CID_IMX_FIM_NUM 65*4882a593Smuzhiyun 66*4882a593SmuzhiyunHow many frame interval measurements to average before comparing against 67*4882a593Smuzhiyunthe nominal frame interval reported by the sensor. This can reduce noise 68*4882a593Smuzhiyuncaused by interrupt latency. 69*4882a593Smuzhiyun 70*4882a593Smuzhiyun- V4L2_CID_IMX_FIM_TOLERANCE_MIN 71*4882a593Smuzhiyun 72*4882a593SmuzhiyunIf the averaged intervals fall outside nominal by this amount, in 73*4882a593Smuzhiyunmicroseconds, the V4L2_EVENT_IMX_FRAME_INTERVAL_ERROR event is sent. 74*4882a593Smuzhiyun 75*4882a593Smuzhiyun- V4L2_CID_IMX_FIM_TOLERANCE_MAX 76*4882a593Smuzhiyun 77*4882a593SmuzhiyunIf any intervals are higher than this value, those samples are 78*4882a593Smuzhiyundiscarded and do not enter into the average. This can be used to 79*4882a593Smuzhiyundiscard really high interval errors that might be due to interrupt 80*4882a593Smuzhiyunlatency from high system load. 81*4882a593Smuzhiyun 82*4882a593Smuzhiyun- V4L2_CID_IMX_FIM_NUM_SKIP 83*4882a593Smuzhiyun 84*4882a593SmuzhiyunHow many frames to skip after a FIM reset or stream restart before 85*4882a593SmuzhiyunFIM begins to average intervals. 86*4882a593Smuzhiyun 87*4882a593Smuzhiyun- V4L2_CID_IMX_FIM_ICAP_CHANNEL / V4L2_CID_IMX_FIM_ICAP_EDGE 88*4882a593Smuzhiyun 89*4882a593SmuzhiyunThese controls will configure an input capture channel as the method 90*4882a593Smuzhiyunfor measuring frame intervals. This is superior to the default method 91*4882a593Smuzhiyunof measuring frame intervals via EOF interrupt, since it is not subject 92*4882a593Smuzhiyunto uncertainty errors introduced by interrupt latency. 93*4882a593Smuzhiyun 94*4882a593SmuzhiyunInput capture requires hardware support. A VSYNC signal must be routed 95*4882a593Smuzhiyunto one of the i.MX6 input capture channel pads. 96*4882a593Smuzhiyun 97*4882a593SmuzhiyunV4L2_CID_IMX_FIM_ICAP_CHANNEL configures which i.MX6 input capture 98*4882a593Smuzhiyunchannel to use. This must be 0 or 1. 99*4882a593Smuzhiyun 100*4882a593SmuzhiyunV4L2_CID_IMX_FIM_ICAP_EDGE configures which signal edge will trigger 101*4882a593Smuzhiyuninput capture events. By default the input capture method is disabled 102*4882a593Smuzhiyunwith a value of IRQ_TYPE_NONE. Set this control to IRQ_TYPE_EDGE_RISING, 103*4882a593SmuzhiyunIRQ_TYPE_EDGE_FALLING, or IRQ_TYPE_EDGE_BOTH to enable input capture, 104*4882a593Smuzhiyuntriggered on the given signal edge(s). 105*4882a593Smuzhiyun 106*4882a593SmuzhiyunWhen input capture is disabled, frame intervals will be measured via 107*4882a593SmuzhiyunEOF interrupt. 108*4882a593Smuzhiyun 109*4882a593Smuzhiyun 110*4882a593SmuzhiyunFile list 111*4882a593Smuzhiyun--------- 112*4882a593Smuzhiyun 113*4882a593Smuzhiyundrivers/staging/media/imx/ 114*4882a593Smuzhiyuninclude/media/imx.h 115*4882a593Smuzhiyuninclude/linux/imx-media.h 116*4882a593Smuzhiyun 117*4882a593Smuzhiyun 118*4882a593SmuzhiyunAuthors 119*4882a593Smuzhiyun------- 120*4882a593Smuzhiyun 121*4882a593Smuzhiyun- Steve Longerbeam <steve_longerbeam@mentor.com> 122*4882a593Smuzhiyun- Philipp Zabel <kernel@pengutronix.de> 123*4882a593Smuzhiyun- Russell King <linux@armlinux.org.uk> 124*4882a593Smuzhiyun 125*4882a593SmuzhiyunCopyright (C) 2012-2017 Mentor Graphics Inc. 126