Re: [PATCH v2 2/2] watchdog: max63xx_wdt: Add support for specifying WDI logic via GPIO

[Guenter Roeck]

On 5/2/22 20:57, Tzung-Bi Shih wrote:
> On Fri, Apr 29, 2022 at 03:13:49PM +0200, Pali Rohár wrote:
> > @@ -27,6 +27,7 @@
> >   #include <linux/io.h>
> >   #include <linux/slab.h>
> >   #include <linux/property.h>
> > +#include <linux/gpio/consumer.h>
>
> It would be better to keep them alphabetically.  Anyway, they aren't sorted
> originally...
>
> > +static void max63xx_gpio_ping(struct max63xx_wdt *wdt)
> > +{
> > +	spin_lock(&wdt->lock);
>
> Does it really need to acquire the lock?  It looks like the lock is to prevent
> concurrent accesses to the mmap in max63xx_mmap_ping() and max63xx_mmap_set().

Actually, that doesn't work at all. spin_lock() directly contradicts
with gpiod_set_value_cansleep().

> > +	gpiod_set_value_cansleep(wdt->gpio_wdi, 1);
> > +	udelay(1);
>
> Doesn't it need to include <linux/delay.h> for udelay()?
>
> > @@ -225,10 +240,19 @@ static int max63xx_wdt_probe(struct platform_device *pdev)
> >   		return -EINVAL;
> >   	}
> >   
> > +	wdt->gpio_wdi = devm_gpiod_get(dev, NULL, GPIOD_FLAGS_BIT_DIR_OUT);
> > +	if (IS_ERR(wdt->gpio_wdi) && PTR_ERR(wdt->gpio_wdi) != -ENOENT)
>
> Use devm_gpiod_get_optional() to make the intent clear.  Also, it gets rid of
> the check for -ENOENT.
>
> > +		return dev_err_probe(dev, PTR_ERR(wdt->gpio_wdi),
> > +				     "unable to request gpio: %ld\n",
> > +				     PTR_ERR(wdt->gpio_wdi));
>
> It doesn't need to again print for PTR_ERR(wdt->gpio_wdi).  dev_err_probe()
> prints the error.
>
> >   	err = max63xx_mmap_init(pdev, wdt);
> >   	if (err)
> >   		return err;
> >   
> > +	if (!IS_ERR(wdt->gpio_wdi))
> > +		wdt->ping = max63xx_gpio_ping;
>
> Thus, the max63xx_gpio_ping() overrides max63xx_mmap_ping() if the GPIO was
> provided?  It would be better to mention the behavior in the commit message.
>
> Also, could both the assignments of `wdt->gpio_wdi` and `wdt->ping` happen
> after max63xx_mmap_init()?