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.\" $FreeBSD$ 27.\" 28.Dd July 7, 2018 29.Dt IMX_WDOG 4 30.Os 31.Sh NAME 32.Nm imx_wdog 33.Nd device driver for the NXP i.MX5 and i.MX6 watchdog timer 34.Sh SYNOPSIS 35To compile this driver into the kernel, 36place the following line in your 37kernel configuration file: 38.Bd -ragged -offset indent 39.Cd "device imxwdt" 40.Ed 41.Pp 42Alternatively, to load the driver as a 43module at boot time, place the following line in 44.Xr loader.conf 5 : 45.Bd -literal -offset indent 46imx_wdog_load="YES" 47.Ed 48.Sh DESCRIPTION 49The 50.Nm 51driver provides 52.Xr watchdog 4 53support for the watchdog timer present on NXP i.MX5 and i.MX6 processors. 54The i.MX watchdog hardware supports programmable timeouts ranging from 550.5 to 128 seconds, in half-second increments. 56Once activated, the watchdog hardware cannot be deactivated, but the 57timeout period can be changed to any valid non-zero value. 58.Pp 59At power-on, a special 16-second 60.Sq power-down timer 61mode is automatically enabled by the hardware. 62It will assert the external WDOG_B signal, which may be connected to 63external hardware that causes the system to reset or power-down. 64The power-down timer is often reset by the boot loader (typically U-Boot). 65If the power-down timer is still active at the time when the normal 66watchdog is first enabled, the 67.Nm 68driver automatically disables it. 69.Pp 70The 71.Nm 72driver supports the FDT 73.Va fsl,external-reset 74property by enabling the assertion of the WDOG_B external timeout signal 75when the property is present. 76When running this way, the need to reset the system due to watchdog 77timeout is signaled by driving the WDOG_B line low; some external 78entity is expected to assert the chip's POR pin in response. 79The 80.Nm 81driver attempts to backstop this external reset by scheduling an 82interrupt to occur as well. 83The interrupt handler waits 1 second for the external reset to occur, 84then it triggers a normal software reset. 85Note that the WDOG_B signal can be configured to use a variety of 86pins on the chip. 87For the 88.Va fsl,external-reset 89property to be effective, the signal must be connected to an appropriate 90pin by the system's FDT pinctrl data. 91.Pp 92The 93.Nm 94driver supports the FDT 95.Va timeout-secs 96property by enabling the watchdog as soon as the driver attaches, 97using the given timeout value. 98This extends watchdog protection to much of the system startup process, 99but it still requires that 100.Xr watchdogd 4 101be configured to service the watchdog. 102.Sh SEE ALSO 103.Xr fdt 4 , 104.Xr watchdog 4 , 105.Xr watchdog 8 , 106.Xr watchdogd 8 , 107.Xr watchdog 9 108.Sh HISTORY 109The 110.Nm 111driver first appeared in 112.Fx 10.0 . 113