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

From: Guenter Roeck
Date: Tue May 03 2022 - 00:37:27 EST


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()?