1.\" 2.\" Copyright (c) 2018 Ian Lepore <ian@freebsd.org> 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25.\" 26.Dd July 7, 2018 27.Dt IMX_WDOG 4 28.Os 29.Sh NAME 30.Nm imx_wdog 31.Nd device driver for the NXP i.MX5 and i.MX6 watchdog timer 32.Sh SYNOPSIS 33To compile this driver into the kernel, 34place the following line in your 35kernel configuration file: 36.Bd -ragged -offset indent 37.Cd "device imxwdt" 38.Ed 39.Pp 40Alternatively, to load the driver as a 41module at boot time, place the following line in 42.Xr loader.conf 5 : 43.Bd -literal -offset indent 44imx_wdog_load="YES" 45.Ed 46.Sh DESCRIPTION 47The 48.Nm 49driver provides 50.Xr watchdog 4 51support for the watchdog timer present on NXP i.MX5 and i.MX6 processors. 52The i.MX watchdog hardware supports programmable timeouts ranging from 530.5 to 128 seconds, in half-second increments. 54Once activated, the watchdog hardware cannot be deactivated, but the 55timeout period can be changed to any valid non-zero value. 56.Pp 57At power-on, a special 16-second 58.Sq power-down timer 59mode is automatically enabled by the hardware. 60It will assert the external WDOG_B signal, which may be connected to 61external hardware that causes the system to reset or power-down. 62The power-down timer is often reset by the boot loader (typically U-Boot). 63If the power-down timer is still active at the time when the normal 64watchdog is first enabled, the 65.Nm 66driver automatically disables it. 67.Pp 68The 69.Nm 70driver supports the FDT 71.Va fsl,external-reset 72property by enabling the assertion of the WDOG_B external timeout signal 73when the property is present. 74When running this way, the need to reset the system due to watchdog 75timeout is signaled by driving the WDOG_B line low; some external 76entity is expected to assert the chip's POR pin in response. 77The 78.Nm 79driver attempts to backstop this external reset by scheduling an 80interrupt to occur as well. 81The interrupt handler waits 1 second for the external reset to occur, 82then it triggers a normal software reset. 83Note that the WDOG_B signal can be configured to use a variety of 84pins on the chip. 85For the 86.Va fsl,external-reset 87property to be effective, the signal must be connected to an appropriate 88pin by the system's FDT pinctrl data. 89.Pp 90The 91.Nm 92driver supports the FDT 93.Va timeout-secs 94property by enabling the watchdog as soon as the driver attaches, 95using the given timeout value. 96This extends watchdog protection to much of the system startup process, 97but it still requires that 98.Xr watchdogd 4 99be configured to service the watchdog. 100.Sh SEE ALSO 101.Xr fdt 4 , 102.Xr watchdog 4 , 103.Xr watchdog 8 , 104.Xr watchdogd 8 , 105.Xr watchdog 9 106.Sh HISTORY 107The 108.Nm 109driver first appeared in 110.Fx 10.0 . 111