watchdog: imx2_wdt: add external reset support via dt prop

The IMX6 watchdog supports assertion of a signal (WDOG_B) which
can be pinmux'd to an external pin. This is typically used for boards that
have PMIC's in control of the IMX6 power rails. In fact, failure to use
such an external reset on boards with external PMIC's can result in various
hangs due to the IMX6 not being fully reset [1] as well as the board failing
to reset because its PMIC has not been reset to provide adequate voltage for
the CPU when coming out of reset at 800Mhz.

This uses a new device-tree property 'fsl,ext-reset-output' to indicate the
board has such a reset and to cause the watchdog to be configured to assert
WDOG_B instead of an internal reset both on a watchdog timeout and in
system_restart.

[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-March/333689.html

Cc: Fabio Estevam <[email protected]>
Cc: Lucas Stach <[email protected]>
Cc: Stefan Roese <[email protected]>
Cc: Iain Paton <[email protected]>
Cc: Sascha Hauer <[email protected]>
Signed-off-by: Tim Harvey <[email protected]>
Reviewed-by: Lucas Stach <[email protected]>
Acked-by: Shawn Guo <[email protected]>
Tested-by: Akshay Bhat <[email protected]>
Signed-off-by: Guenter Roeck <[email protected]>
Signed-off-by: Wim Van Sebroeck <[email protected]>

0 files changed, 0 insertions, 0 deletions