linux-kernel - Re: [PATCH 1/3] watchdog: imx2_wdg: suspend watchdog in WAIT mode

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Date:   Wed, 19 Oct 2022 08:33:06 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Andrej Picej <andrej.picej@...ik.com>
Cc:     linux-watchdog@...r.kernel.org, shawnguo@...nel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-imx@....com, festevam@...il.com,
        kernel@...gutronix.de, s.hauer@...gutronix.de,
        wim@...ux-watchdog.org, robh+dt@...nel.org
Subject: Re: [PATCH 1/3] watchdog: imx2_wdg: suspend watchdog in WAIT mode

On Wed, Oct 19, 2022 at 01:17:12PM +0200, Andrej Picej wrote:
> Putting device into the "Suspend-To-Idle" mode causes watchdog to
> trigger and reset the board after set watchdog timeout period elapses.
> 
> Introduce new device-tree property "fsl,suspend-in-wait" which suspends
> watchdog in WAIT mode. This is done by setting WDW bit in WCR
> (Watchdog Control Register) Watchdog operation is restored after exiting
> WAIT mode as expected. WAIT mode coresponds with Linux's
> "Suspend-To-Idle".
> 

Does that have any impact on suspend/resume handling in the driver,
specifically with the "no_ping" variable used for fsl,imx7d-wdt ?

Thanks,
Guenter

> Signed-off-by: Andrej Picej <andrej.picej@...ik.com>
> ---
>  drivers/watchdog/imx2_wdt.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
> index d0c5d47ddede..150ba83ce176 100644
> --- a/drivers/watchdog/imx2_wdt.c
> +++ b/drivers/watchdog/imx2_wdt.c
> @@ -35,6 +35,7 @@
>  
>  #define IMX2_WDT_WCR		0x00		/* Control Register */
>  #define IMX2_WDT_WCR_WT		(0xFF << 8)	/* -> Watchdog Timeout Field */
> +#define IMX2_WDT_WCR_WDW	BIT(7)		/* -> Watchdog disable for WAIT */
>  #define IMX2_WDT_WCR_WDA	BIT(5)		/* -> External Reset WDOG_B */
>  #define IMX2_WDT_WCR_SRS	BIT(4)		/* -> Software Reset Signal */
>  #define IMX2_WDT_WCR_WRE	BIT(3)		/* -> WDOG Reset Enable */
> @@ -67,6 +68,7 @@ struct imx2_wdt_device {
>  	bool ext_reset;
>  	bool clk_is_on;
>  	bool no_ping;
> +	bool sleep_wait;
>  };
>  
>  static bool nowayout = WATCHDOG_NOWAYOUT;
> @@ -129,6 +131,9 @@ static inline void imx2_wdt_setup(struct watchdog_device *wdog)
>  
>  	/* Suspend timer in low power mode, write once-only */
>  	val |= IMX2_WDT_WCR_WDZST;
> +	/* Suspend timer in low power WAIT mode, write once-only */
> +	if (wdev->sleep_wait)
> +		val |= IMX2_WDT_WCR_WDW;
>  	/* Strip the old watchdog Time-Out value */
>  	val &= ~IMX2_WDT_WCR_WT;
>  	/* Generate internal chip-level reset if WDOG times out */
> @@ -313,6 +318,8 @@ static int __init imx2_wdt_probe(struct platform_device *pdev)
>  
>  	wdev->ext_reset = of_property_read_bool(dev->of_node,
>  						"fsl,ext-reset-output");
> +	wdev->sleep_wait = of_property_read_bool(dev->of_node,
> +						"fsl,suspend-in-wait");
>  	/*
>  	 * The i.MX7D doesn't support low power mode, so we need to ping the watchdog
>  	 * during suspend.
> -- 
> 2.25.1
>