[PATCH v4] gpio: fxl6408: Add suspend/resume support

[Jisheng Zhang <jszhang@kernel.org>]

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

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
---
since v3:
 - simplify the patch a lot by removing fxl6408_chip wrapper structure,
   thank Bart for the suggestion.

since v2:
 - drop the reset pin support patch since no users now

since v1:
 - fix W=1 build error on nios2 platform

 drivers/gpio/gpio-fxl6408.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/gpio/gpio-fxl6408.c b/drivers/gpio/gpio-fxl6408.c
index 86ebc66b1104..afc1b8461dab 100644
--- a/drivers/gpio/gpio-fxl6408.c
+++ b/drivers/gpio/gpio-fxl6408.c
@@ -123,6 +123,8 @@ static int fxl6408_probe(struct i2c_client *client)
 	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)
@@ -131,6 +133,16 @@ static int fxl6408_probe(struct i2c_client *client)
 	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" },
 	{ }
@@ -146,6 +158,7 @@ MODULE_DEVICE_TABLE(i2c, fxl6408_id);
 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,
-- 
2.51.0