power: reset: Add TPS65086 restart driver

The only way to reset the BeagleV Starlight v0.9 board[1] properly is to
tell the PMIC to reset itself which will then assert the external reset
lines of the SoC, USB hub and ethernet phy.

This adds a driver to register a reset handler to do just that.

[1] https://github.com/beagleboard/beaglev-starlight

Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/reset/Kconfig

@@ -204,6 +204,12 @@ config POWER_RESET_ST
 	help
 	  Reset support for STMicroelectronics boards.
 
+config POWER_RESET_TPS65086
+	bool "TPS65086 restart driver"
+	depends on MFD_TPS65086
+	help
+	  This driver adds support for resetting the TPS65086 PMIC on restart.
+
 config POWER_RESET_VERSATILE
 	bool "ARM Versatile family reboot driver"
 	depends on ARM

drivers/power/reset/Makefile

@@ -23,6 +23,7 @@ obj-$(CONFIG_POWER_RESET_QNAP) += qnap-poweroff.o
 obj-$(CONFIG_POWER_RESET_REGULATOR) += regulator-poweroff.o
 obj-$(CONFIG_POWER_RESET_RESTART) += restart-poweroff.o
 obj-$(CONFIG_POWER_RESET_ST) += st-poweroff.o
+obj-$(CONFIG_POWER_RESET_TPS65086) += tps65086-restart.o
 obj-$(CONFIG_POWER_RESET_VERSATILE) += arm-versatile-reboot.o
 obj-$(CONFIG_POWER_RESET_VEXPRESS) += vexpress-poweroff.o
 obj-$(CONFIG_POWER_RESET_XGENE) += xgene-reboot.o

drivers/power/reset/tps65086-restart.c

@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2021 Emil Renner Berthing
+ */
+
+#include <linux/mfd/tps65086.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/reboot.h>
+
+struct tps65086_restart {
+	struct notifier_block handler;
+	struct device *dev;
+};
+
+static int tps65086_restart_notify(struct notifier_block *this,
+				   unsigned long mode, void *cmd)
+{
+	struct tps65086_restart *tps65086_restart =
+		container_of(this, struct tps65086_restart, handler);
+	struct tps65086 *tps65086 = dev_get_drvdata(tps65086_restart->dev->parent);
+	int ret;
+
+	ret = regmap_write(tps65086->regmap, TPS65086_FORCESHUTDN, 1);
+	if (ret) {
+		dev_err(tps65086_restart->dev, "%s: error writing to tps65086 pmic: %d\n",
+			__func__, ret);
+		return NOTIFY_DONE;
+	}
+
+	/* give it a little time */
+	mdelay(200);
+
+	WARN_ON(1);
+
+	return NOTIFY_DONE;
+}
+
+static int tps65086_restart_probe(struct platform_device *pdev)
+{
+	struct tps65086_restart *tps65086_restart;
+	int ret;
+
+	tps65086_restart = devm_kzalloc(&pdev->dev, sizeof(*tps65086_restart), GFP_KERNEL);
+	if (!tps65086_restart)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, tps65086_restart);
+
+	tps65086_restart->handler.notifier_call = tps65086_restart_notify;
+	tps65086_restart->handler.priority = 192;
+	tps65086_restart->dev = &pdev->dev;
+
+	ret = register_restart_handler(&tps65086_restart->handler);
+	if (ret) {
+		dev_err(&pdev->dev, "%s: cannot register restart handler: %d\n",
+			__func__, ret);
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static int tps65086_restart_remove(struct platform_device *pdev)
+{
+	struct tps65086_restart *tps65086_restart = platform_get_drvdata(pdev);
+	int ret;
+
+	ret = unregister_restart_handler(&tps65086_restart->handler);
+	if (ret) {
+		dev_err(&pdev->dev, "%s: cannot unregister restart handler: %d\n",
+			__func__, ret);
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static const struct platform_device_id tps65086_restart_id_table[] = {
+	{ "tps65086-reset", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(platform, tps65086_restart_id_table);
+
+static struct platform_driver tps65086_restart_driver = {
+	.driver = {
+		.name = "tps65086-restart",
+	},
+	.probe = tps65086_restart_probe,
+	.remove = tps65086_restart_remove,
+	.id_table = tps65086_restart_id_table,
+};
+module_platform_driver(tps65086_restart_driver);
+
+MODULE_AUTHOR("Emil Renner Berthing <kernel@esmil.dk>");
+MODULE_DESCRIPTION("TPS65086 restart driver");
+MODULE_LICENSE("GPL v2");