Re: [PATCH v2 1/3] watchdog: imx2_wdg: suspend watchdog in WAIT mode

[Andrej Picej <andrej.picej@xxxxxxxxx>]

Hi Alexander,

On 25. 10. 22 11:38, Alexander Stein wrote:
> Am Dienstag, 25. Oktober 2022, 09:25:31 CEST schrieb Andrej Picej:
> > 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".
> >
> > Signed-off-by: Andrej Picej <andrej.picej@xxxxxxxxx>
> > Reviewed-by: Fabio Estevam <festevam@xxxxxxxxx>
> > ---
> > Changes in v2:
> >   - validate the property with compatible string, as this functionality
> >     is not supported by all devices.
> > ---
> >   drivers/watchdog/imx2_wdt.c | 37 +++++++++++++++++++++++++++++++++++++
> >   1 file changed, 37 insertions(+)
> >
> > diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
> > index d0c5d47ddede..dd9866c6f1e5 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 +68,27 @@ struct imx2_wdt_device {
> >   	bool ext_reset;
> >   	bool clk_is_on;
> >   	bool no_ping;
> > +	bool sleep_wait;
> > +};
> > +
> > +static const char * const wdw_boards[] __initconst = {
> > +	"fsl,imx25-wdt",
> > +	"fsl,imx35-wdt",
> > +	"fsl,imx50-wdt",
> > +	"fsl,imx51-wdt",
> > +	"fsl,imx53-wdt",
> > +	"fsl,imx6q-wdt",
> > +	"fsl,imx6sl-wdt",
> > +	"fsl,imx6sll-wdt",
> > +	"fsl,imx6sx-wdt",
> > +	"fsl,imx6ul-wdt",
> > +	"fsl,imx7d-wdt",
> > +	"fsl,imx8mm-wdt",
> > +	"fsl,imx8mn-wdt",
> > +	"fsl,imx8mp-wdt",
> > +	"fsl,imx8mq-wdt",
> > +	"fsl,vf610-wdt",
> > +	NULL
> >   };
>
> So the models listed in Documentation/devicetree/bindings/watchdog/fsl-imx-
> wdt.yaml not supporting this feature are
> * fsl,imx21-wdt
> * fsl,imx27-wdt
> * fsl,imx31-wdt
> * fsl,ls1012a-wdt
> * fsl,ls1043a-wdt
> ?
yes, you are correct.

> But all models are listed as compatible to fsl,imx21-wdt. So there is
> something wrong here. IMHO this sounds like the compatible list has to be
> split and updated. Depending on that this feature can be detected. Maintaining
> another list seems error prone to me.

So basically the compatible lists would be split into two groups, one 
for the devices which support this WDW bit and the rest which don't 
support this?
You got a point here, but...this means that every processors 
device-tree, which has two compatible strings (with "fsl,imx21-wdt") 
should be updated, right? That sounds like quite a lot of changes, which 
I'd like to avoid if possible.

Best regards,
Andrej

> Best regards,
> Alexander
>
> >   static bool nowayout = WATCHDOG_NOWAYOUT;
> > @@ -129,6 +151,9 @@ 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 +338,18 @@ static int __init imx2_wdt_probe(struct platform_device
> > *pdev)
> >
> >   	wdev->ext_reset = of_property_read_bool(dev->of_node,
> >   						"fsl,ext-
> reset-output");
> > +
> > +	if (of_property_read_bool(dev->of_node, "fsl,suspend-in-wait"))
> > +		if (of_device_compatible_match(dev->of_node,
> wdw_boards))
> > +			wdev->sleep_wait = 1;
> > +		else {
> > +			dev_warn(dev, "Warning: Suspending watchdog
> during " \
> > +				"WAIT mode is not supported for
> this device.\n");
> > +			wdev->sleep_wait = 0;
> > +		}
> > +	else
> > +		wdev->sleep_wait = 0;
> > +
> >   	/*
> >   	 * The i.MX7D doesn't support low power mode, so we need to ping
> the
> > watchdog * during suspend.