Commit bc677ff4 authored by Tim Harvey's avatar Tim Harvey Committed by Wim Van Sebroeck
Browse files

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 <festevam@gmail.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Stefan Roese <sr@denx.de>
Cc: Iain Paton <ipaton0@gmail.com>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: default avatarTim Harvey <tharvey@gateworks.com>
Reviewed-by: default avatarLucas Stach <l.stach@pengutronix.de>
Acked-by: default avatarShawn Guo <shawn.guo@linaro.org>
Tested-by: default avatarAkshay Bhat <akshay.bhat@timesys.com>
Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarWim Van Sebroeck <wim@iguana.be>
parent ebbf677a

Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt

+3 −1
Original line number Diff line number Diff line
@@ -5,10 +5,12 @@ Required properties: 
- reg : Should contain WDT registers location and length

- interrupts : Should contain WDT interrupt



Optional property:

Optional properties:

- big-endian: If present the watchdog device's registers are implemented

  in big endian mode, otherwise in native mode(same with CPU), for more

  detail please see: Documentation/devicetree/bindings/regmap/regmap.txt.

- fsl,ext-reset-output: If present the watchdog device is configured to

  assert its external reset (WDOG_B) instead of issuing a software reset.



Examples:

drivers/watchdog/imx2_wdt.c

+17 −2
Original line number Diff line number Diff line
@@ -37,6 +37,8 @@ 


#define IMX2_WDT_WCR		0x00		/* Control Register */

#define IMX2_WDT_WCR_WT		(0xFF << 8)	/* -> Watchdog Timeout Field */

#define IMX2_WDT_WCR_WDA	(1 << 5)	/* -> External Reset WDOG_B */

#define IMX2_WDT_WCR_SRS	(1 << 4)	/* -> Software Reset Signal */

#define IMX2_WDT_WCR_WRE	(1 << 3)	/* -> WDOG Reset Enable */

#define IMX2_WDT_WCR_WDE	(1 << 2)	/* -> Watchdog Enable */

#define IMX2_WDT_WCR_WDZST	(1 << 0)	/* -> Watchdog timer Suspend */
@@ -59,6 +61,7 @@ struct imx2_wdt_device { 
	struct clk *clk;

	struct regmap *regmap;

	struct watchdog_device wdog;

	bool ext_reset;

};



static bool nowayout = WATCHDOG_NOWAYOUT;
@@ -83,6 +86,12 @@ static int imx2_wdt_restart(struct watchdog_device *wdog, unsigned long action, 
	struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);

	unsigned int wcr_enable = IMX2_WDT_WCR_WDE;



	/* Use internal reset or external - not both */

	if (wdev->ext_reset)

		wcr_enable |= IMX2_WDT_WCR_SRS; /* do not assert int reset */

	else

		wcr_enable |= IMX2_WDT_WCR_WDA; /* do not assert ext-reset */



	/* Assert SRS signal */

	regmap_write(wdev->regmap, IMX2_WDT_WCR, wcr_enable);

	/*
@@ -112,8 +121,12 @@ static inline void imx2_wdt_setup(struct watchdog_device *wdog) 
	val |= IMX2_WDT_WCR_WDZST;

	/* Strip the old watchdog Time-Out value */

	val &= ~IMX2_WDT_WCR_WT;

	/* Generate reset if WDOG times out */

	/* Generate internal chip-level reset if WDOG times out */

	if (!wdev->ext_reset)

		val &= ~IMX2_WDT_WCR_WRE;

	/* Or if external-reset assert WDOG_B reset only on time-out */

	else

		val |= IMX2_WDT_WCR_WRE;

	/* Keep Watchdog Disabled */

	val &= ~IMX2_WDT_WCR_WDE;

	/* Set the watchdog's Time-Out value */
@@ -230,6 +243,8 @@ static int __init imx2_wdt_probe(struct platform_device *pdev) 
	regmap_read(wdev->regmap, IMX2_WDT_WRSR, &val);

	wdog->bootstatus = val & IMX2_WDT_WRSR_TOUT ? WDIOF_CARDRESET : 0;



	wdev->ext_reset = of_property_read_bool(pdev->dev.of_node,

						"fsl,ext-reset-output");

	wdog->timeout = clamp_t(unsigned, timeout, 1, IMX2_WDT_MAX_TIME);

	if (wdog->timeout != timeout)

		dev_warn(&pdev->dev, "Initial timeout out of range! Clamped from %u to %u\n",

CRA Git | Maintained and supported by SUSTech CRA and CCSE