watchdog: add sl28cpld watchdog driver
The watchdog timer is part of the sl28cpld management controller. The
watchdog timer usually supervises the bootloader boot-up and if it bites
the failsafe bootloader will be activated. Apart from that it supports
the usual board level reset and one SMARC speciality: driving the
WDT_TIMEOUT# signal.
Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>
diff --git a/doc/board/kontron/sl28.rst b/doc/board/kontron/sl28.rst
index c7b18be..c2cdc5e 100644
--- a/doc/board/kontron/sl28.rst
+++ b/doc/board/kontron/sl28.rst
@@ -35,23 +35,6 @@
disabled the builtin watchdog you might have to manually enter failsafe
mode by asserting the ``FORCE_RECOV#`` line during board reset.
-Disable the builtin watchdog
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-- boot into the failsafe bootloader, either by asserting the
- ``FORCE_RECOV#`` line or if you still have the original bootloader
- installed you can use the command::
-
- > wdt dev cpld_watchdog@4a; wdt expire 1
-
-- in the failsafe bootloader use the "sl28 nvm" command to disable
- the automatic start of the builtin watchdog::
-
- > sl28 nvm 0008
-
-- power-cycle the board
-
-
Update image
------------
@@ -81,6 +64,42 @@
> i2c md 4a 3.1 1
+
+Builtin watchdog
+----------------
+
+The builtin watchdog will supervise the bootloader startup. If anything
+goes wrong it will reset the board and boot into the failsafe bootloader.
+
+Once the bootloader is started successfully, it will disable the watchdog
+timer.
+
+wdt command flags
+^^^^^^^^^^^^^^^^^
+
+The `wdt start` as well as the `wdt expire` command take a flags argument.
+The supported bitmask is as follows.
+
+| Bit | Description |
+| --- | ----------------------------- |
+| 0 | Enable failsafe mode |
+| 1 | Lock the control register |
+| 2 | Disable board reset |
+| 3 | Enable WDT_TIME_OUT# line |
+
+For example, you can use `wdt expire 1` to issue a reset and boot into the
+failsafe bootloader.
+
+Disable the builtin watchdog
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+If for some reason, this isn't a desired behavior, the watchdog can also
+be configured to not be enabled on board reset. It's configuration is saved
+in the non-volatile board configuration bits. To change these you can use
+the `sl28 nvm` command.
+
+For more information on the non-volatile board configuration bits, see the
+following section.
Non-volatile Board Configuration Bits
-------------------------------------