text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   *
   * Copyright (C) 2012 ARM Limited
   */
  
  #include <linux/delay.h>
  #include <linux/notifier.h>
  #include <linux/of.h>
  #include <linux/of_device.h>
  #include <linux/platform_device.h>
  #include <linux/reboot.h>
  #include <linux/stat.h>
  #include <linux/vexpress.h>
  
  static void vexpress_reset_do(struct device *dev, const char *what)
  {
  	int err = -ENOENT;
  	struct regmap *reg = dev_get_drvdata(dev);
  
  	if (reg) {
  		err = regmap_write(reg, 0, 0);
  		if (!err)
  			mdelay(1000);
  	}
  
  	dev_emerg(dev, "Unable to %s (%d)\n", what, err);
  }
  
  static struct device *vexpress_power_off_device;
  static atomic_t vexpress_restart_nb_refcnt = ATOMIC_INIT(0);
  
  static void vexpress_power_off(void)
  {
  	vexpress_reset_do(vexpress_power_off_device, "power off");
  }
  
  static struct device *vexpress_restart_device;
  
  static int vexpress_restart(struct notifier_block *this, unsigned long mode,
  			     void *cmd)
  {
  	vexpress_reset_do(vexpress_restart_device, "restart");
  
  	return NOTIFY_DONE;
  }
  
  static struct notifier_block vexpress_restart_nb = {
  	.notifier_call = vexpress_restart,
  	.priority = 128,
  };
  
  static ssize_t vexpress_reset_active_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	return sprintf(buf, "%d\n", vexpress_restart_device == dev);
  }
  
  static ssize_t vexpress_reset_active_store(struct device *dev,
  		struct device_attribute *attr, const char *buf, size_t count)
  {
  	long value;
  	int err = kstrtol(buf, 0, &value);
  
  	if (!err && value)
  		vexpress_restart_device = dev;
  
  	return err ? err : count;
  }
  
  static DEVICE_ATTR(active, S_IRUGO | S_IWUSR, vexpress_reset_active_show,
  		   vexpress_reset_active_store);
  
  
  enum vexpress_reset_func { FUNC_RESET, FUNC_SHUTDOWN, FUNC_REBOOT };
  
  static const struct of_device_id vexpress_reset_of_match[] = {
  	{
  		.compatible = "arm,vexpress-reset",
  		.data = (void *)FUNC_RESET,
  	}, {
  		.compatible = "arm,vexpress-shutdown",
  		.data = (void *)FUNC_SHUTDOWN
  	}, {
  		.compatible = "arm,vexpress-reboot",
  		.data = (void *)FUNC_REBOOT
  	},
  	{}
  };
  
  static int _vexpress_register_restart_handler(struct device *dev)
  {
  	int err;
  
  	vexpress_restart_device = dev;
  	if (atomic_inc_return(&vexpress_restart_nb_refcnt) == 1) {
  		err = register_restart_handler(&vexpress_restart_nb);
  		if (err) {
  			dev_err(dev, "cannot register restart handler (err=%d)\n", err);
  			atomic_dec(&vexpress_restart_nb_refcnt);
  			return err;
  		}
  	}
  	device_create_file(dev, &dev_attr_active);
  
  	return 0;
  }
  
  static int vexpress_reset_probe(struct platform_device *pdev)
  {
  	const struct of_device_id *match =
  			of_match_device(vexpress_reset_of_match, &pdev->dev);
  	struct regmap *regmap;
  	int ret = 0;
  
  	if (!match)
  		return -EINVAL;
  
  	regmap = devm_regmap_init_vexpress_config(&pdev->dev);
  	if (IS_ERR(regmap))
  		return PTR_ERR(regmap);
  	dev_set_drvdata(&pdev->dev, regmap);
  
  	switch ((enum vexpress_reset_func)match->data) {
  	case FUNC_SHUTDOWN:
  		vexpress_power_off_device = &pdev->dev;
  		pm_power_off = vexpress_power_off;
  		break;
  	case FUNC_RESET:
  		if (!vexpress_restart_device)
  			ret = _vexpress_register_restart_handler(&pdev->dev);
  		break;
  	case FUNC_REBOOT:
  		ret = _vexpress_register_restart_handler(&pdev->dev);
  		break;
  	}
  
  	return ret;
  }
  
  static struct platform_driver vexpress_reset_driver = {
  	.probe = vexpress_reset_probe,
  	.driver = {
  		.name = "vexpress-reset",
  		.of_match_table = vexpress_reset_of_match,
  		.suppress_bind_attrs = true,
  	},
  };
  builtin_platform_driver(vexpress_reset_driver);
  