i.MX51 EVK Linux Reference Manual
Freescale Semiconductor
31-1
Chapter 31
Watchdog (WDOG) Driver
The Watchdog Timer module protects against system failures by providing an escape from unexpected
hang or infinite loop situations or programming errors. Some platforms may have two WDOG modules
with one of them having interrupt capability.
31.1
Hardware Operation
Once the WDOG timer is activated, it must be serviced by software on a periodic basis. If servicing does
not take place in time, the WDOG times out. Upon a time-out, the WDOG either asserts the
wdog_b
signal
or a
wdog_rst_b
system reset signal, depending on software configuration. The watchdog module cannot
be deactivated once it is activated.
31.2
Software Operation
The Linux OS has a standard WDOG interface that allows support of a WDOG driver for a specific
platform. WDOG can be suspended/resumed in STOP/DOZE and WAIT modes independently. Since
some bits of the WGOD registers are only one-time programmable after booting, ensure these registers are
written correctly.
31.3
Generic WDOG Driver
The generic WGOD driver is implemented in the
<ltib_dir>/rpm/BUILD/linux/drivers/watchdog/mxc_wdt.c
file. It provides functions for various IOCTLs
and read/write calls from the user level program to control the WDOG.
31.3.1
Driver Features
This WDOG implementation includes the following features:
•
Generates the reset signal if it is enabled but not serviced within a predefined timeout value
(defined in milliseconds in one of the WDOG source files)
•
Does not generate the reset signal if it is serviced within a predefined timeout value
•
Provides IOCTL/read/write required by the standard WDOG subsystem
31.3.2
Menu Configuration Options
The following Linux kernel configuration option is provided for this module. To get to this option, use the
./ltib -c
command when located in the
<ltib dir>
. On the screen displayed, select
Configure the
Kernel
and exit. When the next screen appears, select the following option to enable this module:
Summary of Contents for i.MX51 EVK
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Page 38: ...Machine Specific Layer MSL i MX51 EVK Linux Reference Manual 2 8 Freescale Semiconductor...
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