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

[Andrej Picej <andrej.picej@xxxxxxxxx>]

On 25. 10. 22 16:21, Guenter Roeck wrote:
> On 10/25/22 00:25, 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.
>
> s/reset/resets/
>
> > 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
>
> '.' after ')' missing ?
>
> > WAIT mode as expected. WAIT mode coresponds with Linux's
>
> s/coresponds/corresponds/
Will fix this in v3, thank you.

> > "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
> >   };
> >   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;
>
> Since sleep_wait is bool:
>              wdev->sleep_wait = true;
>
> > +        else {
> > +            dev_warn(dev, "Warning: Suspending watchdog during " \
> > +                "WAIT mode is not supported for this device.\n");
>
> Do not split strings. "Warning:" is redundant. Please handle the error 
> first.
>
> > +            wdev->sleep_wait = 0;
>
> Unnecessary; false by default. Also, this should fail and return -EINVAL.
> Devicetree files should be correct, and warning messages tend to be 
> ignored.
>
> > +        }
>
> All branches of if/else need to wither use {} or no {}.
>
> > +    else
> > +        wdev->sleep_wait = 0;
> > +
> Unnecessary.
>
> I would suggest to replace the above code with something like
>
>      if (of_property_read_bool(dev->of_node, "fsl,suspend-in-wait")) {
>          if (!of_device_compatible_match(dev->of_node, wdw_boards)) {
>              dev_err(dev, "Suspending watchdog in WAIT mode is not 
> supported for this device\n");
>              return -EINVAL;
>          }
>          wdev->sleep_wait = true;
>      }

OK, this look cleaner, will use this, thanks.

> >       /*
> >        * The i.MX7D doesn't support low power mode, so we need to ping 
> > the watchdog
> >        * during suspend.
>
> I still wonder how that interacts with fsl,suspend-in-wait, but since we 
> have a
> property for that we can leave that for someone else to find out. Maybe 
> add a
> comment explaining that interaction with "fsl,suspend-in-wait" is unknown.
I'm assuming that i.MX7D doesn't enter any of low-power modes including 
WAIT mode. If this is the case the watchdog wouldn't get disabled.

Anyway, I will add a short comment regarding the unknown behaviour of 
this property with i.MX7D device.

Best regards,
Andrej