// SPDX-License-Identifier: GPL-2.0-only

  /*
   * Driver for voltage controller regulators
   *
   * Copyright (C) 2017 Google, Inc.

   */
  
  #include <linux/delay.h>
  #include <linux/err.h>
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/of.h>
  #include <linux/of_device.h>

  #include <linux/regulator/coupler.h>

  #include <linux/regulator/driver.h>
  #include <linux/regulator/of_regulator.h>
  #include <linux/sort.h>

  #include "internal.h"

  struct vctrl_voltage_range {
  	int min_uV;
  	int max_uV;
  };
  
  struct vctrl_voltage_ranges {
  	struct vctrl_voltage_range ctrl;
  	struct vctrl_voltage_range out;
  };
  
  struct vctrl_voltage_table {
  	int ctrl;
  	int out;
  	int ovp_min_sel;
  };
  
  struct vctrl_data {
  	struct regulator_dev *rdev;
  	struct regulator_desc desc;
  	struct regulator *ctrl_reg;
  	bool enabled;
  	unsigned int min_slew_down_rate;
  	unsigned int ovp_threshold;
  	struct vctrl_voltage_ranges vrange;
  	struct vctrl_voltage_table *vtable;
  	unsigned int sel;
  };
  
  static int vctrl_calc_ctrl_voltage(struct vctrl_data *vctrl, int out_uV)
  {
  	struct vctrl_voltage_range *ctrl = &vctrl->vrange.ctrl;
  	struct vctrl_voltage_range *out = &vctrl->vrange.out;
  
  	return ctrl->min_uV +
  		DIV_ROUND_CLOSEST_ULL((s64)(out_uV - out->min_uV) *
  				      (ctrl->max_uV - ctrl->min_uV),
  				      out->max_uV - out->min_uV);
  }
  
  static int vctrl_calc_output_voltage(struct vctrl_data *vctrl, int ctrl_uV)
  {
  	struct vctrl_voltage_range *ctrl = &vctrl->vrange.ctrl;
  	struct vctrl_voltage_range *out = &vctrl->vrange.out;
  
  	if (ctrl_uV < 0) {
  		pr_err("vctrl: failed to get control voltage
  ");
  		return ctrl_uV;
  	}
  
  	if (ctrl_uV < ctrl->min_uV)
  		return out->min_uV;
  
  	if (ctrl_uV > ctrl->max_uV)
  		return out->max_uV;
  
  	return out->min_uV +
  		DIV_ROUND_CLOSEST_ULL((s64)(ctrl_uV - ctrl->min_uV) *
  				      (out->max_uV - out->min_uV),
  				      ctrl->max_uV - ctrl->min_uV);
  }
  
  static int vctrl_get_voltage(struct regulator_dev *rdev)
  {
  	struct vctrl_data *vctrl = rdev_get_drvdata(rdev);

  	int ctrl_uV = regulator_get_voltage_rdev(vctrl->ctrl_reg->rdev);

  
  	return vctrl_calc_output_voltage(vctrl, ctrl_uV);
  }
  
  static int vctrl_set_voltage(struct regulator_dev *rdev,
  			     int req_min_uV, int req_max_uV,
  			     unsigned int *selector)
  {
  	struct vctrl_data *vctrl = rdev_get_drvdata(rdev);
  	struct regulator *ctrl_reg = vctrl->ctrl_reg;

  	int orig_ctrl_uV = regulator_get_voltage_rdev(ctrl_reg->rdev);

  	int uV = vctrl_calc_output_voltage(vctrl, orig_ctrl_uV);
  	int ret;
  
  	if (req_min_uV >= uV || !vctrl->ovp_threshold)
  		/* voltage rising or no OVP */

  		return regulator_set_voltage_rdev(ctrl_reg->rdev,

  			vctrl_calc_ctrl_voltage(vctrl, req_min_uV),

  			vctrl_calc_ctrl_voltage(vctrl, req_max_uV),
  			PM_SUSPEND_ON);

  
  	while (uV > req_min_uV) {
  		int max_drop_uV = (uV * vctrl->ovp_threshold) / 100;
  		int next_uV;
  		int next_ctrl_uV;
  		int delay;
  
  		/* Make sure no infinite loop even in crazy cases */
  		if (max_drop_uV == 0)
  			max_drop_uV = 1;
  
  		next_uV = max_t(int, req_min_uV, uV - max_drop_uV);
  		next_ctrl_uV = vctrl_calc_ctrl_voltage(vctrl, next_uV);

  		ret = regulator_set_voltage_rdev(ctrl_reg->rdev,
  					    next_ctrl_uV,

  					    next_ctrl_uV,

  					    PM_SUSPEND_ON);

  		if (ret)
  			goto err;
  
  		delay = DIV_ROUND_UP(uV - next_uV, vctrl->min_slew_down_rate);
  		usleep_range(delay, delay + DIV_ROUND_UP(delay, 10));
  
  		uV = next_uV;
  	}
  
  	return 0;
  
  err:
  	/* Try to go back to original voltage */

  	regulator_set_voltage_rdev(ctrl_reg->rdev, orig_ctrl_uV, orig_ctrl_uV,
  				   PM_SUSPEND_ON);

  
  	return ret;
  }
  
  static int vctrl_get_voltage_sel(struct regulator_dev *rdev)
  {
  	struct vctrl_data *vctrl = rdev_get_drvdata(rdev);
  
  	return vctrl->sel;
  }
  
  static int vctrl_set_voltage_sel(struct regulator_dev *rdev,
  				 unsigned int selector)
  {
  	struct vctrl_data *vctrl = rdev_get_drvdata(rdev);
  	struct regulator *ctrl_reg = vctrl->ctrl_reg;
  	unsigned int orig_sel = vctrl->sel;
  	int ret;
  
  	if (selector >= rdev->desc->n_voltages)
  		return -EINVAL;
  
  	if (selector >= vctrl->sel || !vctrl->ovp_threshold) {
  		/* voltage rising or no OVP */

  		ret = regulator_set_voltage_rdev(ctrl_reg->rdev,
  					    vctrl->vtable[selector].ctrl,

  					    vctrl->vtable[selector].ctrl,

  					    PM_SUSPEND_ON);

  		if (!ret)
  			vctrl->sel = selector;
  
  		return ret;
  	}
  
  	while (vctrl->sel != selector) {
  		unsigned int next_sel;
  		int delay;
  
  		if (selector >= vctrl->vtable[vctrl->sel].ovp_min_sel)
  			next_sel = selector;
  		else
  			next_sel = vctrl->vtable[vctrl->sel].ovp_min_sel;

  		ret = regulator_set_voltage_rdev(ctrl_reg->rdev,

  					    vctrl->vtable[next_sel].ctrl,

  					    vctrl->vtable[next_sel].ctrl,
  					    PM_SUSPEND_ON);

  		if (ret) {
  			dev_err(&rdev->dev,
  				"failed to set control voltage to %duV
  ",
  				vctrl->vtable[next_sel].ctrl);
  			goto err;
  		}
  		vctrl->sel = next_sel;
  
  		delay = DIV_ROUND_UP(vctrl->vtable[vctrl->sel].out -
  				     vctrl->vtable[next_sel].out,
  				     vctrl->min_slew_down_rate);
  		usleep_range(delay, delay + DIV_ROUND_UP(delay, 10));
  	}
  
  	return 0;
  
  err:
  	if (vctrl->sel != orig_sel) {
  		/* Try to go back to original voltage */

  		if (!regulator_set_voltage_rdev(ctrl_reg->rdev,
  					   vctrl->vtable[orig_sel].ctrl,

  					   vctrl->vtable[orig_sel].ctrl,

  					   PM_SUSPEND_ON))

  			vctrl->sel = orig_sel;
  		else
  			dev_warn(&rdev->dev,
  				 "failed to restore original voltage
  ");
  	}
  
  	return ret;
  }
  
  static int vctrl_list_voltage(struct regulator_dev *rdev,
  			      unsigned int selector)
  {
  	struct vctrl_data *vctrl = rdev_get_drvdata(rdev);
  
  	if (selector >= rdev->desc->n_voltages)
  		return -EINVAL;
  
  	return vctrl->vtable[selector].out;
  }
  
  static int vctrl_parse_dt(struct platform_device *pdev,
  			  struct vctrl_data *vctrl)
  {
  	int ret;
  	struct device_node *np = pdev->dev.of_node;
  	u32 pval;
  	u32 vrange_ctrl[2];
  
  	vctrl->ctrl_reg = devm_regulator_get(&pdev->dev, "ctrl");
  	if (IS_ERR(vctrl->ctrl_reg))
  		return PTR_ERR(vctrl->ctrl_reg);
  
  	ret = of_property_read_u32(np, "ovp-threshold-percent", &pval);
  	if (!ret) {
  		vctrl->ovp_threshold = pval;
  		if (vctrl->ovp_threshold > 100) {
  			dev_err(&pdev->dev,
  				"ovp-threshold-percent (%u) > 100
  ",
  				vctrl->ovp_threshold);
  			return -EINVAL;
  		}
  	}
  
  	ret = of_property_read_u32(np, "min-slew-down-rate", &pval);
  	if (!ret) {
  		vctrl->min_slew_down_rate = pval;
  
  		/* We use the value as int and as divider; sanity check */
  		if (vctrl->min_slew_down_rate == 0) {
  			dev_err(&pdev->dev,
  				"min-slew-down-rate must not be 0
  ");
  			return -EINVAL;
  		} else if (vctrl->min_slew_down_rate > INT_MAX) {
  			dev_err(&pdev->dev, "min-slew-down-rate (%u) too big
  ",
  				vctrl->min_slew_down_rate);
  			return -EINVAL;
  		}
  	}
  
  	if (vctrl->ovp_threshold && !vctrl->min_slew_down_rate) {
  		dev_err(&pdev->dev,
  			"ovp-threshold-percent requires min-slew-down-rate
  ");
  		return -EINVAL;
  	}
  
  	ret = of_property_read_u32(np, "regulator-min-microvolt", &pval);
  	if (ret) {
  		dev_err(&pdev->dev,
  			"failed to read regulator-min-microvolt: %d
  ", ret);
  		return ret;
  	}
  	vctrl->vrange.out.min_uV = pval;
  
  	ret = of_property_read_u32(np, "regulator-max-microvolt", &pval);
  	if (ret) {
  		dev_err(&pdev->dev,
  			"failed to read regulator-max-microvolt: %d
  ", ret);
  		return ret;
  	}
  	vctrl->vrange.out.max_uV = pval;
  
  	ret = of_property_read_u32_array(np, "ctrl-voltage-range", vrange_ctrl,
  					 2);
  	if (ret) {
  		dev_err(&pdev->dev, "failed to read ctrl-voltage-range: %d
  ",
  			ret);
  		return ret;
  	}
  
  	if (vrange_ctrl[0] >= vrange_ctrl[1]) {
  		dev_err(&pdev->dev, "ctrl-voltage-range is invalid: %d-%d
  ",
  			vrange_ctrl[0], vrange_ctrl[1]);
  		return -EINVAL;
  	}
  
  	vctrl->vrange.ctrl.min_uV = vrange_ctrl[0];
  	vctrl->vrange.ctrl.max_uV = vrange_ctrl[1];
  
  	return 0;
  }
  
  static int vctrl_cmp_ctrl_uV(const void *a, const void *b)
  {
  	const struct vctrl_voltage_table *at = a;
  	const struct vctrl_voltage_table *bt = b;
  
  	return at->ctrl - bt->ctrl;
  }
  
  static int vctrl_init_vtable(struct platform_device *pdev)
  {
  	struct vctrl_data *vctrl = platform_get_drvdata(pdev);
  	struct regulator_desc *rdesc = &vctrl->desc;
  	struct regulator *ctrl_reg = vctrl->ctrl_reg;
  	struct vctrl_voltage_range *vrange_ctrl = &vctrl->vrange.ctrl;
  	int n_voltages;
  	int ctrl_uV;
  	int i, idx_vt;
  
  	n_voltages = regulator_count_voltages(ctrl_reg);
  
  	rdesc->n_voltages = n_voltages;
  
  	/* determine number of steps within the range of the vctrl regulator */
  	for (i = 0; i < n_voltages; i++) {
  		ctrl_uV = regulator_list_voltage(ctrl_reg, i);
  
  		if (ctrl_uV < vrange_ctrl->min_uV ||

  		    ctrl_uV > vrange_ctrl->max_uV)

  			rdesc->n_voltages--;

  	}
  
  	if (rdesc->n_voltages == 0) {
  		dev_err(&pdev->dev, "invalid configuration
  ");
  		return -EINVAL;
  	}

  	vctrl->vtable = devm_kcalloc(&pdev->dev, rdesc->n_voltages,
  				     sizeof(struct vctrl_voltage_table),
  				     GFP_KERNEL);

  	if (!vctrl->vtable)
  		return -ENOMEM;
  
  	/* create mapping control <=> output voltage */
  	for (i = 0, idx_vt = 0; i < n_voltages; i++) {
  		ctrl_uV = regulator_list_voltage(ctrl_reg, i);
  
  		if (ctrl_uV < vrange_ctrl->min_uV ||
  		    ctrl_uV > vrange_ctrl->max_uV)
  			continue;
  
  		vctrl->vtable[idx_vt].ctrl = ctrl_uV;
  		vctrl->vtable[idx_vt].out =
  			vctrl_calc_output_voltage(vctrl, ctrl_uV);
  		idx_vt++;
  	}
  
  	/* we rely on the table to be ordered by ascending voltage */
  	sort(vctrl->vtable, rdesc->n_voltages,
  	     sizeof(struct vctrl_voltage_table), vctrl_cmp_ctrl_uV,
  	     NULL);
  
  	/* pre-calculate OVP-safe downward transitions */

  	for (i = rdesc->n_voltages - 1; i > 0; i--) {

  		int j;
  		int ovp_min_uV = (vctrl->vtable[i].out *
  				  (100 - vctrl->ovp_threshold)) / 100;
  
  		for (j = 0; j < i; j++) {
  			if (vctrl->vtable[j].out >= ovp_min_uV) {
  				vctrl->vtable[i].ovp_min_sel = j;
  				break;
  			}
  		}
  
  		if (j == i) {
  			dev_warn(&pdev->dev, "switching down from %duV may cause OVP shutdown
  ",
  				vctrl->vtable[i].out);
  			/* use next lowest voltage */
  			vctrl->vtable[i].ovp_min_sel = i - 1;
  		}
  	}
  
  	return 0;
  }
  
  static int vctrl_enable(struct regulator_dev *rdev)
  {
  	struct vctrl_data *vctrl = rdev_get_drvdata(rdev);
  	int ret = regulator_enable(vctrl->ctrl_reg);
  
  	if (!ret)
  		vctrl->enabled = true;
  
  	return ret;
  }
  
  static int vctrl_disable(struct regulator_dev *rdev)
  {
  	struct vctrl_data *vctrl = rdev_get_drvdata(rdev);
  	int ret = regulator_disable(vctrl->ctrl_reg);
  
  	if (!ret)
  		vctrl->enabled = false;
  
  	return ret;
  }
  
  static int vctrl_is_enabled(struct regulator_dev *rdev)
  {
  	struct vctrl_data *vctrl = rdev_get_drvdata(rdev);
  
  	return vctrl->enabled;
  }
  
  static const struct regulator_ops vctrl_ops_cont = {
  	.enable		  = vctrl_enable,
  	.disable	  = vctrl_disable,
  	.is_enabled	  = vctrl_is_enabled,
  	.get_voltage	  = vctrl_get_voltage,
  	.set_voltage	  = vctrl_set_voltage,
  };
  
  static const struct regulator_ops vctrl_ops_non_cont = {
  	.enable		  = vctrl_enable,
  	.disable	  = vctrl_disable,
  	.is_enabled	  = vctrl_is_enabled,
  	.set_voltage_sel = vctrl_set_voltage_sel,
  	.get_voltage_sel = vctrl_get_voltage_sel,
  	.list_voltage    = vctrl_list_voltage,
  	.map_voltage     = regulator_map_voltage_iterate,
  };
  
  static int vctrl_probe(struct platform_device *pdev)
  {
  	struct device_node *np = pdev->dev.of_node;
  	struct vctrl_data *vctrl;
  	const struct regulator_init_data *init_data;
  	struct regulator_desc *rdesc;
  	struct regulator_config cfg = { };
  	struct vctrl_voltage_range *vrange_ctrl;
  	int ctrl_uV;
  	int ret;
  
  	vctrl = devm_kzalloc(&pdev->dev, sizeof(struct vctrl_data),
  			     GFP_KERNEL);
  	if (!vctrl)
  		return -ENOMEM;
  
  	platform_set_drvdata(pdev, vctrl);
  
  	ret = vctrl_parse_dt(pdev, vctrl);
  	if (ret)
  		return ret;
  
  	vrange_ctrl = &vctrl->vrange.ctrl;
  
  	rdesc = &vctrl->desc;
  	rdesc->name = "vctrl";
  	rdesc->type = REGULATOR_VOLTAGE;
  	rdesc->owner = THIS_MODULE;
  
  	if ((regulator_get_linear_step(vctrl->ctrl_reg) == 1) ||
  	    (regulator_count_voltages(vctrl->ctrl_reg) == -EINVAL)) {
  		rdesc->continuous_voltage_range = true;
  		rdesc->ops = &vctrl_ops_cont;
  	} else {
  		rdesc->ops = &vctrl_ops_non_cont;
  	}
  
  	init_data = of_get_regulator_init_data(&pdev->dev, np, rdesc);
  	if (!init_data)
  		return -ENOMEM;
  
  	cfg.of_node = np;
  	cfg.dev = &pdev->dev;
  	cfg.driver_data = vctrl;
  	cfg.init_data = init_data;
  
  	if (!rdesc->continuous_voltage_range) {
  		ret = vctrl_init_vtable(pdev);
  		if (ret)
  			return ret;

  		ctrl_uV = regulator_get_voltage_rdev(vctrl->ctrl_reg->rdev);

  		if (ctrl_uV < 0) {
  			dev_err(&pdev->dev, "failed to get control voltage
  ");
  			return ctrl_uV;
  		}
  
  		/* determine current voltage selector from control voltage */
  		if (ctrl_uV < vrange_ctrl->min_uV) {
  			vctrl->sel = 0;
  		} else if (ctrl_uV > vrange_ctrl->max_uV) {
  			vctrl->sel = rdesc->n_voltages - 1;
  		} else {
  			int i;
  
  			for (i = 0; i < rdesc->n_voltages; i++) {
  				if (ctrl_uV == vctrl->vtable[i].ctrl) {
  					vctrl->sel = i;
  					break;
  				}
  			}
  		}
  	}
  
  	vctrl->rdev = devm_regulator_register(&pdev->dev, rdesc, &cfg);
  	if (IS_ERR(vctrl->rdev)) {
  		ret = PTR_ERR(vctrl->rdev);
  		dev_err(&pdev->dev, "failed to register regulator: %d
  ", ret);
  		return ret;
  	}
  
  	return 0;
  }
  
  static const struct of_device_id vctrl_of_match[] = {
  	{ .compatible = "vctrl-regulator", },
  	{},
  };
  MODULE_DEVICE_TABLE(of, vctrl_of_match);
  
  static struct platform_driver vctrl_driver = {
  	.probe		= vctrl_probe,
  	.driver		= {
  		.name		= "vctrl-regulator",
  		.of_match_table = of_match_ptr(vctrl_of_match),
  	},
  };
  
  module_platform_driver(vctrl_driver);
  
  MODULE_DESCRIPTION("Voltage Controlled Regulator Driver");
  MODULE_AUTHOR("Matthias Kaehlcke <mka@chromium.org>");
  MODULE_LICENSE("GPL v2");