mfd: rohm-bd71828: Add power off functionality

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

Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
Acked-by: Matti Vaittinen <mazziesaccount@gmail.com>
Link: https://lore.kernel.org/r/20240402111700.494004-3-andreas@kemnade.info
Signed-off-by: Lee Jones <lee@kernel.org>

Author: akemnade

drivers/mfd/rohm-bd71828.c

@@ -464,6 +464,27 @@ 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)
+{
+	while (true) {
+		s32 val;
+
+		/* We are not allowed to sleep, so do not use regmap involving mutexes here. */
+		val = i2c_smbus_read_byte_data(bd71828_dev, BD71828_REG_PS_CTRL_1);
+		if (val >= 0)
+			i2c_smbus_write_byte_data(bd71828_dev,
+						  BD71828_REG_PS_CTRL_1,
+						  BD71828_MASK_STATE_HBNT | (u8)val);
+		mdelay(500);
+	}
+}
+
+static void bd71828_remove_poweroff(void *data)
+{
+	pm_power_off = NULL;
+}
+
 static int bd71828_i2c_probe(struct i2c_client *i2c)
 {
 	struct regmap_irq_chip_data *irq_data;
@@ -542,7 +563,20 @@ 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) &&
+	    chip_type == ROHM_CHIP_TYPE_BD71828) {
+		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;
 }

include/linux/mfd/rohm-bd71828.h

@@ -4,6 +4,7 @@
 #ifndef __LINUX_MFD_BD71828_H__
 #define __LINUX_MFD_BD71828_H__
 
+#include <linux/bits.h>
 #include <linux/mfd/rohm-generic.h>
 #include <linux/mfd/rohm-shared.h>
 
@@ -41,6 +42,8 @@ enum {
 #define BD71828_REG_PS_CTRL_2		0x05
 #define BD71828_REG_PS_CTRL_3		0x06
 
+#define BD71828_MASK_STATE_HBNT		BIT(1)
+
 //#define BD71828_REG_SWRESET		0x06
 #define BD71828_MASK_RUN_LVL_CTRL	0x30