[PATCH 1/2] watchdog: imx2_wdt: add external reset support via 'ext-reset' dt property

[l.stach@pengutronix.de (Lucas Stach)]

Am Donnerstag, den 28.05.2015, 15:54 -0700 schrieb Tim Harvey:
> 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 voltate for
> the CPU when comming out of reset at 800Mhz.
> 
> This uses a new device-tree property 'ext-reset' 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
> 
> Signed-off-by: Tim Harvey <tharvey@gateworks.com>
> ---
>  .../devicetree/bindings/watchdog/fsl-imx-wdt.txt       |  2 ++
>  drivers/watchdog/imx2_wdt.c                            | 18 ++++++++++++++++--
>  2 files changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt b/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt
> index 8dab6fd..14e04ac 100644
> --- a/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt
> +++ b/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt
> @@ -9,6 +9,8 @@ Optional property:
>  - 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.
> +- ext-reset: If present the watchdog device is configured to assert its
> +  external reset (WDOG_B) instead of issuing a software reset.
>  

Probably a bit of personal taste, but I would prefer the naming to
include the property that this is a output. So something like
"ext-reset-output".
 
>  Examples:
>  
> diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
> index 5e6d808..9ffd516 100644
> --- a/drivers/watchdog/imx2_wdt.c
> +++ b/drivers/watchdog/imx2_wdt.c
> @@ -41,6 +41,8 @@
>  
>  #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 Assert */
> +#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 */
> @@ -65,6 +67,7 @@ struct imx2_wdt_device {
>  	struct timer_list timer;	/* Pings the watchdog when closed */
>  	struct watchdog_device wdog;
>  	struct notifier_block restart_handler;
> +	bool ext_reset;
>  };
>  
>  static bool nowayout = WATCHDOG_NOWAYOUT;
> @@ -86,10 +89,17 @@ static const struct watchdog_info imx2_wdt_info = {
>  static int imx2_restart_handler(struct notifier_block *this, unsigned long mode,
>  				void *cmd)
>  {
> -	unsigned int wcr_enable = IMX2_WDT_WCR_WDE;
> +	unsigned int wcr_enable;
>  	struct imx2_wdt_device *wdev = container_of(this,
>  						    struct imx2_wdt_device,
>  						    restart_handler);
> +
> +	if (!wdev->ext_reset)
> +		wcr_enable = IMX2_WDT_WCR_WDE;
> +	/* Use external reset */
> +	else
> +		wcr_enable = IMX2_WDT_WCR_WDE | IMX2_WDT_WCR_SRS;
> +

This doesn't look nice. Please write this simply as:

if (wdev->ext_reset)
	wcr_enable |= IMX2_WDT_WCR_SRS;

>  	/* Assert SRS signal */
>  	regmap_write(wdev->regmap, 0, wcr_enable);
>  	/*
> @@ -120,7 +130,10 @@ static inline void imx2_wdt_setup(struct watchdog_device *wdog)
>  	/* Strip the old watchdog Time-Out value */
>  	val &= ~IMX2_WDT_WCR_WT;
>  	/* Generate reset if WDOG times out */
> -	val &= ~IMX2_WDT_WCR_WRE;
> +	if (!wdev->ext_reset)
> +		val &= ~IMX2_WDT_WCR_WRE;
> +	else
> +		val |= IMX2_WDT_WCR_WRE;	/* assert WDOG_B on time-out */

The comment above this sections doesn't seem to match the code anymore
after your change.

>  	/* Keep Watchdog Disabled */
>  	val &= ~IMX2_WDT_WCR_WDE;
>  	/* Set the watchdog's Time-Out value */
> @@ -262,6 +275,7 @@ 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, "ext-reset");
>  	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",

-- 
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