[PATCH] drivers: mfd: da9063: Add restart notifier implementation

[Alexandre Ghiti]

The SiFive Unmatched board uses the da9063 PMIC for reset: add a restart
notifier that will execute a small i2c sequence allowing to reset the
board.

The original implementation comes from Marcus Comstedt and Anders Montonen
(https://forums.sifive.com/t/reboot-command/4721/28).

Signed-off-by: Alexandre Ghiti <alexandre.ghiti@xxxxxxxxxxxxx>
---
 drivers/mfd/da9063-core.c       | 25 +++++++++++++++++++++++++
 include/linux/mfd/da9063/core.h |  3 +++
 2 files changed, 28 insertions(+)

diff --git a/drivers/mfd/da9063-core.c b/drivers/mfd/da9063-core.c
index df407c3afce3..c87b8d611f20 100644
--- a/drivers/mfd/da9063-core.c
+++ b/drivers/mfd/da9063-core.c
@@ -20,6 +20,7 @@
 #include <linux/mutex.h>
 #include <linux/mfd/core.h>
 #include <linux/regmap.h>
+#include <linux/reboot.h>
 
 #include <linux/mfd/da9063/core.h>
 #include <linux/mfd/da9063/registers.h>
@@ -158,6 +159,18 @@ static int da9063_clear_fault_log(struct da9063 *da9063)
 	return ret;
 }
 
+static int da9063_restart_notify(struct notifier_block *this,
+				 unsigned long mode, void *cmd)
+{
+	struct da9063 *da9063 = container_of(this, struct da9063, restart_handler);
+
+	regmap_write(da9063->regmap, DA9063_REG_PAGE_CON, 0x00);
+	regmap_write(da9063->regmap, DA9063_REG_CONTROL_F, 0x04);
+	regmap_write(da9063->regmap, DA9063_REG_CONTROL_A, 0x68);
+
+	return NOTIFY_DONE;
+}
+
 int da9063_device_init(struct da9063 *da9063, unsigned int irq)
 {
 	int ret;
@@ -197,6 +210,18 @@ int da9063_device_init(struct da9063 *da9063, unsigned int irq)
 		}
 	}
 
+	da9063->restart_handler.notifier_call = da9063_restart_notify;
+	da9063->restart_handler.priority = 128;
+	ret = register_restart_handler(&da9063->restart_handler);
+	if (ret) {
+		dev_err(da9063->dev, "Failed to register restart handler\n");
+		return ret;
+	}
+
+	devm_add_action(da9063->dev,
+			(void (*)(void *))unregister_restart_handler,
+			&da9063->restart_handler);
+
 	return ret;
 }
 
diff --git a/include/linux/mfd/da9063/core.h b/include/linux/mfd/da9063/core.h
index fa7a43f02f27..1b20c498e340 100644
--- a/include/linux/mfd/da9063/core.h
+++ b/include/linux/mfd/da9063/core.h
@@ -85,6 +85,9 @@ struct da9063 {
 	int		chip_irq;
 	unsigned int	irq_base;
 	struct regmap_irq_chip_data *regmap_irq;
+
+	/* Restart */
+	struct notifier_block restart_handler;
 };
 
 int da9063_device_init(struct da9063 *da9063, unsigned int irq);
-- 
2.30.2