gpio: fxl6408: Add suspend/resume support

Currently, during suspend, do nothing; during resume, just sync the
regmap cache to hw regs.

Signed-off-by: Jisheng Zhang <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Bartosz Golaszewski <[e-mail]>

drivers/gpio/gpio-fxl6408.c

···
 	if (ret)
 		return ret;
 
+	i2c_set_clientdata(client, gpio_config.regmap);
+
 	/* Disable High-Z of outputs, so that our OUTPUT updates actually take effect. */
 	ret = regmap_write(gpio_config.regmap, FXL6408_REG_OUTPUT_HIGH_Z, 0);
 	if (ret)
···
 
 	return PTR_ERR_OR_ZERO(devm_gpio_regmap_register(dev, &gpio_config));
 }
+
+static int fxl6408_resume(struct device *dev)
+{
+	struct regmap *regmap = dev_get_drvdata(dev);
+
+	regcache_mark_dirty(regmap);
+	return regcache_sync(regmap);
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(fxl6408_pm_ops, NULL, fxl6408_resume);
 
 static const __maybe_unused struct of_device_id fxl6408_dt_ids[] = {
 	{ .compatible = "fcs,fxl6408" },
···
 static struct i2c_driver fxl6408_driver = {
 	.driver = {
 		.name	= "fxl6408",
+		.pm	= pm_sleep_ptr(&fxl6408_pm_ops),
 		.of_match_table = fxl6408_dt_ids,
 	},
 	.probe		= fxl6408_probe,