watchdog: da9063: use atomic safe i2c transfer in reset handler

This patch is based on commit 057b52b ("watchdog: da9062: make restart
handler atomic safe"), which uses the atomic transfer capability of the
i2c framework.

Signed-off-by: Yunus Bas <y.bas@phytec.de>
Signed-off-by: Andrej Picej <andrej.picej@norik.com>
Reviewed-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20211124080654.2601135-1-andrej.picej@norik.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/da9063_wdt.c

@@ -14,6 +14,7 @@
 #include <linux/platform_device.h>
 #include <linux/uaccess.h>
 #include <linux/slab.h>
+#include <linux/i2c.h>
 #include <linux/delay.h>
 #include <linux/mfd/da9063/registers.h>
 #include <linux/mfd/da9063/core.h>
@@ -169,14 +170,19 @@ static int da9063_wdt_restart(struct watchdog_device *wdd, unsigned long action,
 			      void *data)
 {
 	struct da9063 *da9063 = watchdog_get_drvdata(wdd);
+	struct i2c_client *client = to_i2c_client(da9063->dev);
 	int ret;
 
-	ret = regmap_write(da9063->regmap, DA9063_REG_CONTROL_F,
-			   DA9063_SHUTDOWN);
-	if (ret)
+	/* Don't use regmap because it is not atomic safe */
+	ret = i2c_smbus_write_byte_data(client, DA9063_REG_CONTROL_F,
+					DA9063_SHUTDOWN);
+	if (ret < 0)
 		dev_alert(da9063->dev, "Failed to shutdown (err = %d)\n",
 			  ret);
 
+	/* wait for reset to assert... */
+	mdelay(500);
+
 	return ret;
 }