/*
 * Copyright (c) 2015 Linaro Ltd.
 * Author: Pi-Cheng Chen <pi-cheng.chen@linaro.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/clk.h>
#include <linux/cpu.h>
#include <linux/cpu_cooling.h>
#include <linux/cpufreq.h>
#include <linux/cpumask.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pm_opp.h>
#include <linux/regulator/consumer.h>
#include <linux/slab.h>
#include <linux/thermal.h>

#define MIN_VOLT_SHIFT		(100000)
#define MAX_VOLT_SHIFT		(200000)
#define MAX_VOLT_LIMIT		(1150000)
#define VOLT_TOL		(10000)

/*
 * The struct mtk_cpu_dvfs_info holds necessary information for doing CPU DVFS
 * on each CPU power/clock domain of Mediatek SoCs. Each CPU cluster in
 * Mediatek SoCs has two voltage inputs, Vproc and Vsram. In some cases the two
 * voltage inputs need to be controlled under a hardware limitation:
 * 100mV < Vsram - Vproc < 200mV
 *
 * When scaling the clock frequency of a CPU clock domain, the clock source
 * needs to be switched to another stable PLL clock temporarily until
 * the original PLL becomes stable at target frequency.
 */
struct mtk_cpu_dvfs_info {
	struct device *cpu_dev;
	struct regulator *proc_reg;
	struct regulator *sram_reg;
	struct clk *cpu_clk;
	struct clk *inter_clk;
	struct thermal_cooling_device *cdev;
	int intermediate_voltage;
	bool need_voltage_tracking;
};

static int mtk_cpufreq_voltage_tracking(struct mtk_cpu_dvfs_info *info,
					int new_vproc)
{
	struct regulator *proc_reg = info->proc_reg;
	struct regulator *sram_reg = info->sram_reg;
	int old_vproc, old_vsram, new_vsram, vsram, vproc, ret;

	old_vproc = regulator_get_voltage(proc_reg);
	if (old_vproc < 0) {
		pr_err("%s: invalid Vproc value: %d\n", __func__, old_vproc);
		return old_vproc;
	}
	/* Vsram should not exceed the maximum allowed voltage of SoC. */
	new_vsram = min(new_vproc + MIN_VOLT_SHIFT, MAX_VOLT_LIMIT);

	if (old_vproc < new_vproc) {
		/*
		 * When scaling up voltages, Vsram and Vproc scale up step
		 * by step. At each step, set Vsram to (Vproc + 200mV) first,
		 * then set Vproc to (Vsram - 100mV).
		 * Keep doing it until Vsram and Vproc hit target voltages.
		 */
		do {
			old_vsram = regulator_get_voltage(sram_reg);
			if (old_vsram < 0) {
				pr_err("%s: invalid Vsram value: %d\n",
				       __func__, old_vsram);
				return old_vsram;
			}
			old_vproc = regulator_get_voltage(proc_reg);
			if (old_vproc < 0) {
				pr_err("%s: invalid Vproc value: %d\n",
				       __func__, old_vproc);
				return old_vproc;
			}

			vsram = min(new_vsram, old_vproc + MAX_VOLT_SHIFT);

			if (vsram + VOLT_TOL >= MAX_VOLT_LIMIT) {
				vsram = MAX_VOLT_LIMIT;

				/*
				 * If the target Vsram hits the maximum voltage,
				 * try to set the exact voltage value first.
				 */
				ret = regulator_set_voltage(sram_reg, vsram,
							    vsram);
				if (ret)
					ret = regulator_set_voltage(sram_reg,
							vsram - VOLT_TOL,
							vsram);

				vproc = new_vproc;
			} else {
				ret = regulator_set_voltage(sram_reg, vsram,
							    vsram + VOLT_TOL);

				vproc = vsram - MIN_VOLT_SHIFT;
			}
			if (ret)
				return ret;

			ret = regulator_set_voltage(proc_reg, vproc,
						    vproc + VOLT_TOL);
			if (ret) {
				regulator_set_voltage(sram_reg, old_vsram,
						      old_vsram);
				return ret;
			}
		} while (vproc < new_vproc || vsram < new_vsram);
	} else if (old_vproc > new_vproc) {
		/*
		 * When scaling down voltages, Vsram and Vproc scale down step
		 * by step. At each step, set Vproc to (Vsram - 200mV) first,
		 * then set Vproc to (Vproc + 100mV).
		 * Keep doing it until Vsram and Vproc hit target voltages.
		 */
		do {
			old_vproc = regulator_get_voltage(proc_reg);
			if (old_vproc < 0) {
				pr_err("%s: invalid Vproc value: %d\n",
				       __func__, old_vproc);
				return old_vproc;
			}
			old_vsram = regulator_get_voltage(sram_reg);
			if (old_vsram < 0) {
				pr_err("%s: invalid Vsram value: %d\n",
				       __func__, old_vsram);
				return old_vsram;
			}

			vproc = max(new_vproc, old_vsram - MAX_VOLT_SHIFT);
			ret = regulator_set_voltage(proc_reg, vproc,
						    vproc + VOLT_TOL);
			if (ret)
				return ret;

			if (vproc == new_vproc)
				vsram = new_vsram;
			else
				vsram = max(new_vsram, vproc + MIN_VOLT_SHIFT);

			if (vsram + VOLT_TOL >= MAX_VOLT_LIMIT) {
				vsram = MAX_VOLT_LIMIT;

				/*
				 * If the target Vsram hits the maximum voltage,
				 * try to set the exact voltage value first.
				 */
				ret = regulator_set_voltage(sram_reg, vsram,
							    vsram);
				if (ret)
					ret = regulator_set_voltage(sram_reg,
							vsram - VOLT_TOL,
							vsram);
			} else {
				ret = regulator_set_voltage(sram_reg, vsram,
							    vsram + VOLT_TOL);
			}

			if (ret) {
				regulator_set_voltage(proc_reg, old_vproc,
						      old_vproc);
				return ret;
			}
		} while (vproc > new_vproc + VOLT_TOL ||
			 vsram > new_vsram + VOLT_TOL);
	}

	return 0;
}

static int mtk_cpufreq_set_voltage(struct mtk_cpu_dvfs_info *info, int vproc)
{
	if (info->need_voltage_tracking)
		return mtk_cpufreq_voltage_tracking(info, vproc);
	else
		return regulator_set_voltage(info->proc_reg, vproc,
					     vproc + VOLT_TOL);
}

static int mtk_cpufreq_set_target(struct cpufreq_policy *policy,
				  unsigned int index)
{
	struct cpufreq_frequency_table *freq_table = policy->freq_table;
	struct clk *cpu_clk = policy->clk;
	struct clk *armpll = clk_get_parent(cpu_clk);
	struct mtk_cpu_dvfs_info *info = policy->driver_data;
	struct device *cpu_dev = info->cpu_dev;
	struct dev_pm_opp *opp;
	long freq_hz, old_freq_hz;
	int vproc, old_vproc, inter_vproc, target_vproc, ret;

	inter_vproc = info->intermediate_voltage;

	old_freq_hz = clk_get_rate(cpu_clk);
	old_vproc = regulator_get_voltage(info->proc_reg);
	if (old_vproc < 0) {
		pr_err("%s: invalid Vproc value: %d\n", __func__, old_vproc);
		return old_vproc;
	}

	freq_hz = freq_table[index].frequency * 1000;

	rcu_read_lock();
	opp = dev_pm_opp_find_freq_ceil(cpu_dev, &freq_hz);
	if (IS_ERR(opp)) {
		rcu_read_unlock();
		pr_err("cpu%d: failed to find OPP for %ld\n",
		       policy->cpu, freq_hz);
		return PTR_ERR(opp);
	}
	vproc = dev_pm_opp_get_voltage(opp);
	rcu_read_unlock();

	/*
	 * If the new voltage or the intermediate voltage is higher than the
	 * current voltage, scale up voltage first.
	 */
	target_vproc = (inter_vproc > vproc) ? inter_vproc : vproc;
	if (old_vproc < target_vproc) {
		ret = mtk_cpufreq_set_voltage(info, target_vproc);
		if (ret) {
			pr_err("cpu%d: failed to scale up voltage!\n",
			       policy->cpu);
			mtk_cpufreq_set_voltage(info, old_vproc);
			return ret;
		}
	}

	/* Reparent the CPU clock to intermediate clock. */
	ret = clk_set_parent(cpu_clk, info->inter_clk);
	if (ret) {
		pr_err("cpu%d: failed to re-parent cpu clock!\n",
		       policy->cpu);
		mtk_cpufreq_set_voltage(info, old_vproc);
		WARN_ON(1);
		return ret;
	}

	/* Set the original PLL to target rate. */
	ret = clk_set_rate(armpll, freq_hz);
	if (ret) {
		pr_err("cpu%d: failed to scale cpu clock rate!\n",
		       policy->cpu);
		clk_set_parent(cpu_clk, armpll);
		mtk_cpufreq_set_voltage(info, old_vproc);
		return ret;
	}

	/* Set parent of CPU clock back to the original PLL. */
	ret = clk_set_parent(cpu_clk, armpll);
	if (ret) {
		pr_err("cpu%d: failed to re-parent cpu clock!\n",
		       policy->cpu);
		mtk_cpufreq_set_voltage(info, inter_vproc);
		WARN_ON(1);
		return ret;
	}

	/*
	 * If the new voltage is lower than the intermediate voltage or the
	 * original voltage, scale down to the new voltage.
	 */
	if (vproc < inter_vproc || vproc < old_vproc) {
		ret = mtk_cpufreq_set_voltage(info, vproc);
		if (ret) {
			pr_err("cpu%d: failed to scale down voltage!\n",
			       policy->cpu);
			clk_set_parent(cpu_clk, info->inter_clk);
			clk_set_rate(armpll, old_freq_hz);
			clk_set_parent(cpu_clk, armpll);
			return ret;
		}
	}

	return 0;
}

static void mtk_cpufreq_ready(struct cpufreq_policy *policy)
{
	struct mtk_cpu_dvfs_info *info = policy->driver_data;
	struct device_node *np = of_node_get(info->cpu_dev->of_node);

	if (WARN_ON(!np))
		return;

	if (of_find_property(np, "#cooling-cells", NULL)) {
		info->cdev = of_cpufreq_cooling_register(np,
							 policy->related_cpus);

		if (IS_ERR(info->cdev)) {
			dev_err(info->cpu_dev,
				"running cpufreq without cooling device: %ld\n",
				PTR_ERR(info->cdev));

			info->cdev = NULL;
		}
	}

	of_node_put(np);
}

static int mtk_cpu_dvfs_info_init(struct mtk_cpu_dvfs_info *info, int cpu)
{
	struct device *cpu_dev;
	struct regulator *proc_reg = ERR_PTR(-ENODEV);
	struct regulator *sram_reg = ERR_PTR(-ENODEV);
	struct clk *cpu_clk = ERR_PTR(-ENODEV);
	struct clk *inter_clk = ERR_PTR(-ENODEV);
	struct dev_pm_opp *opp;
	unsigned long rate;
	int ret;

	cpu_dev = get_cpu_device(cpu);
	if (!cpu_dev) {
		pr_err("failed to get cpu%d device\n", cpu);
		return -ENODEV;
	}

	cpu_clk = clk_get(cpu_dev, "cpu");
	if (IS_ERR(cpu_clk)) {
		if (PTR_ERR(cpu_clk) == -EPROBE_DEFER)
			pr_warn("cpu clk for cpu%d not ready, retry.\n", cpu);
		else
			pr_err("failed to get cpu clk for cpu%d\n", cpu);

		ret = PTR_ERR(cpu_clk);
		return ret;
	}

	inter_clk = clk_get(cpu_dev, "intermediate");
	if (IS_ERR(inter_clk)) {
		if (PTR_ERR(inter_clk) == -EPROBE_DEFER)
			pr_warn("intermediate clk for cpu%d not ready, retry.\n",
				cpu);
		else
			pr_err("failed to get intermediate clk for cpu%d\n",
			       cpu);

		ret = PTR_ERR(inter_clk);
		goto out_free_resources;
	}

	proc_reg = regulator_get_exclusive(cpu_dev, "proc");
	if (IS_ERR(proc_reg)) {
		if (PTR_ERR(proc_reg) == -EPROBE_DEFER)
			pr_warn("proc regulator for cpu%d not ready, retry.\n",
				cpu);
		else
			pr_err("failed to get proc regulator for cpu%d\n",
			       cpu);

		ret = PTR_ERR(proc_reg);
		goto out_free_resources;
	}

	/* Both presence and absence of sram regulator are valid cases. */
	sram_reg = regulator_get_exclusive(cpu_dev, "sram");

	ret = dev_pm_opp_of_add_table(cpu_dev);
	if (ret) {
		pr_warn("no OPP table for cpu%d\n", cpu);
		goto out_free_resources;
	}

	/* Search a safe voltage for intermediate frequency. */
	rate = clk_get_rate(inter_clk);
	rcu_read_lock();
	opp = dev_pm_opp_find_freq_ceil(cpu_dev, &rate);
	if (IS_ERR(opp)) {
		rcu_read_unlock();
		pr_err("failed to get intermediate opp for cpu%d\n", cpu);
		ret = PTR_ERR(opp);
		goto out_free_opp_table;
	}
	info->intermediate_voltage = dev_pm_opp_get_voltage(opp);
	rcu_read_unlock();

	info->cpu_dev = cpu_dev;
	info->proc_reg = proc_reg;
	info->sram_reg = IS_ERR(sram_reg) ? NULL : sram_reg;
	info->cpu_clk = cpu_clk;
	info->inter_clk = inter_clk;

	/*
	 * If SRAM regulator is present, software "voltage tracking" is needed
	 * for this CPU power domain.
	 */
	info->need_voltage_tracking = !IS_ERR(sram_reg);

	return 0;

out_free_opp_table:
	dev_pm_opp_of_remove_table(cpu_dev);

out_free_resources:
	if (!IS_ERR(proc_reg))
		regulator_put(proc_reg);
	if (!IS_ERR(sram_reg))
		regulator_put(sram_reg);
	if (!IS_ERR(cpu_clk))
		clk_put(cpu_clk);
	if (!IS_ERR(inter_clk))
		clk_put(inter_clk);

	return ret;
}

static void mtk_cpu_dvfs_info_release(struct mtk_cpu_dvfs_info *info)
{
	if (!IS_ERR(info->proc_reg))
		regulator_put(info->proc_reg);
	if (!IS_ERR(info->sram_reg))
		regulator_put(info->sram_reg);
	if (!IS_ERR(info->cpu_clk))
		clk_put(info->cpu_clk);
	if (!IS_ERR(info->inter_clk))
		clk_put(info->inter_clk);

	dev_pm_opp_of_remove_table(info->cpu_dev);
}

static int mtk_cpufreq_init(struct cpufreq_policy *policy)
{
	struct mtk_cpu_dvfs_info *info;
	struct cpufreq_frequency_table *freq_table;
	int ret;

	info = kzalloc(sizeof(*info), GFP_KERNEL);
	if (!info)
		return -ENOMEM;

	ret = mtk_cpu_dvfs_info_init(info, policy->cpu);
	if (ret) {
		pr_err("%s failed to initialize dvfs info for cpu%d\n",
		       __func__, policy->cpu);
		goto out_free_dvfs_info;
	}

	ret = dev_pm_opp_init_cpufreq_table(info->cpu_dev, &freq_table);
	if (ret) {
		pr_err("failed to init cpufreq table for cpu%d: %d\n",
		       policy->cpu, ret);
		goto out_release_dvfs_info;
	}

	ret = cpufreq_table_validate_and_show(policy, freq_table);
	if (ret) {
		pr_err("%s: invalid frequency table: %d\n", __func__, ret);
		goto out_free_cpufreq_table;
	}

	/* CPUs in the same cluster share a clock and power domain. */
	cpumask_copy(policy->cpus, &cpu_topology[policy->cpu].core_sibling);
	policy->driver_data = info;
	policy->clk = info->cpu_clk;

	return 0;

out_free_cpufreq_table:
	dev_pm_opp_free_cpufreq_table(info->cpu_dev, &freq_table);

out_release_dvfs_info:
	mtk_cpu_dvfs_info_release(info);

out_free_dvfs_info:
	kfree(info);

	return ret;
}

static int mtk_cpufreq_exit(struct cpufreq_policy *policy)
{
	struct mtk_cpu_dvfs_info *info = policy->driver_data;

	cpufreq_cooling_unregister(info->cdev);
	dev_pm_opp_free_cpufreq_table(info->cpu_dev, &policy->freq_table);
	mtk_cpu_dvfs_info_release(info);
	kfree(info);

	return 0;
}

static struct cpufreq_driver mt8173_cpufreq_driver = {
	.flags = CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK |
		 CPUFREQ_HAVE_GOVERNOR_PER_POLICY,
	.verify = cpufreq_generic_frequency_table_verify,
	.target_index = mtk_cpufreq_set_target,
	.get = cpufreq_generic_get,
	.init = mtk_cpufreq_init,
	.exit = mtk_cpufreq_exit,
	.ready = mtk_cpufreq_ready,
	.name = "mtk-cpufreq",
	.attr = cpufreq_generic_attr,
};

static int mt8173_cpufreq_probe(struct platform_device *pdev)
{
	int ret;

	ret = cpufreq_register_driver(&mt8173_cpufreq_driver);
	if (ret)
		pr_err("failed to register mtk cpufreq driver\n");

	return ret;
}

static struct platform_driver mt8173_cpufreq_platdrv = {
	.driver = {
		.name	= "mt8173-cpufreq",
	},
	.probe		= mt8173_cpufreq_probe,
};

static int mt8173_cpufreq_driver_init(void)
{
	struct platform_device *pdev;
	int err;

	if (!of_machine_is_compatible("mediatek,mt8173"))
		return -ENODEV;

	err = platform_driver_register(&mt8173_cpufreq_platdrv);
	if (err)
		return err;

	/*
	 * Since there's no place to hold device registration code and no
	 * device tree based way to match cpufreq driver yet, both the driver
	 * and the device registration codes are put here to handle defer
	 * probing.
	 */
	pdev = platform_device_register_simple("mt8173-cpufreq", -1, NULL, 0);
	if (IS_ERR(pdev)) {
		pr_err("failed to register mtk-cpufreq platform device\n");
		return PTR_ERR(pdev);
	}

	return 0;
}
device_initcall(mt8173_cpufreq_driver_init);