[RFC PATCH 2/2] mfd: rohm-bd71828: Add power off functionality

[Andreas Kemnade <andreas@kemnade.info>]

Since the chip can power off the system, add the corresponding
functionality.
Based on https://github.com/kobolabs/Kobo-Reader/raw/master/hw/imx6sll-clara2e/kernel.tar.bz2
No information source about the magic numbers found.

Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
---
 drivers/mfd/rohm-bd71828.c | 31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/drivers/mfd/rohm-bd71828.c b/drivers/mfd/rohm-bd71828.c
index 594718f7e8e1..5a55aa3620d0 100644
--- a/drivers/mfd/rohm-bd71828.c
+++ b/drivers/mfd/rohm-bd71828.c
@@ -464,6 +464,24 @@ static int set_clk_mode(struct device *dev, struct regmap *regmap,
 				  OUT32K_MODE_CMOS);
 }
 
+static struct i2c_client *bd71828_dev;
+static void bd71828_power_off(void)
+{
+	i2c_smbus_write_byte_data(bd71828_dev, 0x03, 0xff);
+	mdelay(500);
+	i2c_smbus_write_byte_data(bd71828_dev, BD71828_REG_INT_DCIN2, 0x02);
+	mdelay(500);
+	while (true) {
+		i2c_smbus_write_byte_data(bd71828_dev, BD71828_REG_PS_CTRL_1, 0x02);
+		mdelay(500);
+	}
+}
+
+static void bd71828_remove_poweroff(void *data)
+{
+	bd71828_dev = NULL;
+}
+
 static int bd71828_i2c_probe(struct i2c_client *i2c)
 {
 	struct regmap_irq_chip_data *irq_data;
@@ -542,7 +560,18 @@ static int bd71828_i2c_probe(struct i2c_client *i2c)
 	ret = devm_mfd_add_devices(&i2c->dev, PLATFORM_DEVID_AUTO, mfd, cells,
 				   NULL, 0, regmap_irq_get_domain(irq_data));
 	if (ret)
-		dev_err_probe(&i2c->dev, ret, "Failed to create subdevices\n");
+		return	dev_err_probe(&i2c->dev, ret, "Failed to create subdevices\n");
+
+	if (of_device_is_system_power_controller(i2c->dev.of_node)) {
+		if (!pm_power_off) {
+			bd71828_dev = i2c;
+			pm_power_off = bd71828_power_off;
+			ret = devm_add_action_or_reset(&i2c->dev,
+						       bd71828_remove_poweroff,
+						       NULL);
+		} else
+			dev_warn(&i2c->dev, "Poweroff callback already assigned\n");
+	}
 
 	return ret;
 }
-- 
2.39.2