// SPDX-License-Identifier: GPL-2.0-only
/*
 * Apple SoC CPU cluster performance state driver
 *
 * Copyright The Asahi Linux Contributors
 *
 * Based on scpi-cpufreq.c
 */

#include <linux/bitfield.h>
#include <linux/bitops.h>
#include <linux/cpu.h>
#include <linux/cpufreq.h>
#include <linux/cpumask.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/pm_opp.h>
#include <linux/slab.h>

#define APPLE_DVFS_CMD			0x20
#define APPLE_DVFS_CMD_BUSY		BIT(31)
#define APPLE_DVFS_CMD_SET		BIT(25)
#define APPLE_DVFS_CMD_PS2		GENMASK(16, 12)
#define APPLE_DVFS_CMD_PS1		GENMASK(4, 0)

/* Same timebase as CPU counter (24MHz) */
#define APPLE_DVFS_LAST_CHG_TIME	0x38

/*
 * Apple ran out of bits and had to shift this in T8112...
 */
#define APPLE_DVFS_STATUS			0x50
#define APPLE_DVFS_STATUS_CUR_PS_T8103		GENMASK(7, 4)
#define APPLE_DVFS_STATUS_CUR_PS_SHIFT_T8103	4
#define APPLE_DVFS_STATUS_TGT_PS_T8103		GENMASK(3, 0)
#define APPLE_DVFS_STATUS_CUR_PS_T8112		GENMASK(9, 5)
#define APPLE_DVFS_STATUS_CUR_PS_SHIFT_T8112	5
#define APPLE_DVFS_STATUS_TGT_PS_T8112		GENMASK(4, 0)

/*
 * Div is +1, base clock is 12MHz on existing SoCs.
 * For documentation purposes. We use the OPP table to
 * get the frequency.
 */
#define APPLE_DVFS_PLL_STATUS		0xc0
#define APPLE_DVFS_PLL_FACTOR		0xc8
#define APPLE_DVFS_PLL_FACTOR_MULT	GENMASK(31, 16)
#define APPLE_DVFS_PLL_FACTOR_DIV	GENMASK(15, 0)

#define APPLE_DVFS_TRANSITION_TIMEOUT 100

struct apple_soc_cpufreq_info {
	u64 max_pstate;
	u64 cur_pstate_mask;
	u64 cur_pstate_shift;
};

struct apple_cpu_priv {
	struct device *cpu_dev;
	void __iomem *reg_base;
	const struct apple_soc_cpufreq_info *info;
};

static struct cpufreq_driver apple_soc_cpufreq_driver;

static const struct apple_soc_cpufreq_info soc_t8103_info = {
	.max_pstate = 15,
	.cur_pstate_mask = APPLE_DVFS_STATUS_CUR_PS_T8103,
	.cur_pstate_shift = APPLE_DVFS_STATUS_CUR_PS_SHIFT_T8103,
};

static const struct apple_soc_cpufreq_info soc_t8112_info = {
	.max_pstate = 31,
	.cur_pstate_mask = APPLE_DVFS_STATUS_CUR_PS_T8112,
	.cur_pstate_shift = APPLE_DVFS_STATUS_CUR_PS_SHIFT_T8112,
};

static const struct apple_soc_cpufreq_info soc_default_info = {
	.max_pstate = 15,
	.cur_pstate_mask = 0, /* fallback */
};

static const struct of_device_id apple_soc_cpufreq_of_match[] __maybe_unused = {
	{
		.compatible = "apple,t8103-cluster-cpufreq",
		.data = &soc_t8103_info,
	},
	{
		.compatible = "apple,t8112-cluster-cpufreq",
		.data = &soc_t8112_info,
	},
	{
		.compatible = "apple,cluster-cpufreq",
		.data = &soc_default_info,
	},
	{}
};

static unsigned int apple_soc_cpufreq_get_rate(unsigned int cpu)
{
	struct cpufreq_policy *policy = cpufreq_cpu_get_raw(cpu);
	struct apple_cpu_priv *priv = policy->driver_data;
	struct cpufreq_frequency_table *p;
	unsigned int pstate;

	if (priv->info->cur_pstate_mask) {
		u64 reg = readq_relaxed(priv->reg_base + APPLE_DVFS_STATUS);

		pstate = (reg & priv->info->cur_pstate_mask) >>  priv->info->cur_pstate_shift;
	} else {
		/*
		 * For the fallback case we might not know the layout of DVFS_STATUS,
		 * so just use the command register value (which ignores boost limitations).
		 */
		u64 reg = readq_relaxed(priv->reg_base + APPLE_DVFS_CMD);

		pstate = FIELD_GET(APPLE_DVFS_CMD_PS1, reg);
	}

	cpufreq_for_each_valid_entry(p, policy->freq_table)
		if (p->driver_data == pstate)
			return p->frequency;

	dev_err(priv->cpu_dev, "could not find frequency for pstate %d\n",
		pstate);
	return 0;
}

static int apple_soc_cpufreq_set_target(struct cpufreq_policy *policy,
					unsigned int index)
{
	struct apple_cpu_priv *priv = policy->driver_data;
	unsigned int pstate = policy->freq_table[index].driver_data;
	u64 reg;

	/* Fallback for newer SoCs */
	if (index > priv->info->max_pstate)
		index = priv->info->max_pstate;

	if (readq_poll_timeout_atomic(priv->reg_base + APPLE_DVFS_CMD, reg,
				      !(reg & APPLE_DVFS_CMD_BUSY), 2,
				      APPLE_DVFS_TRANSITION_TIMEOUT)) {
		return -EIO;
	}

	reg &= ~(APPLE_DVFS_CMD_PS1 | APPLE_DVFS_CMD_PS2);
	reg |= FIELD_PREP(APPLE_DVFS_CMD_PS1, pstate);
	reg |= FIELD_PREP(APPLE_DVFS_CMD_PS2, pstate);
	reg |= APPLE_DVFS_CMD_SET;

	writeq_relaxed(reg, priv->reg_base + APPLE_DVFS_CMD);

	return 0;
}

static unsigned int apple_soc_cpufreq_fast_switch(struct cpufreq_policy *policy,
						  unsigned int target_freq)
{
	if (apple_soc_cpufreq_set_target(policy, policy->cached_resolved_idx) < 0)
		return 0;

	return policy->freq_table[policy->cached_resolved_idx].frequency;
}

static int apple_soc_cpufreq_find_cluster(struct cpufreq_policy *policy,
					  void __iomem **reg_base,
					  const struct apple_soc_cpufreq_info **info)
{
	struct of_phandle_args args;
	const struct of_device_id *match;
	int ret = 0;

	ret = of_perf_domain_get_sharing_cpumask(policy->cpu, "performance-domains",
						 "#performance-domain-cells",
						 policy->cpus, &args);
	if (ret < 0)
		return ret;

	match = of_match_node(apple_soc_cpufreq_of_match, args.np);
	of_node_put(args.np);
	if (!match)
		return -ENODEV;

	*info = match->data;

	*reg_base = of_iomap(args.np, 0);
	if (!*reg_base)
		return -ENOMEM;

	return 0;
}

static struct freq_attr *apple_soc_cpufreq_hw_attr[] = {
	&cpufreq_freq_attr_scaling_available_freqs,
	NULL, /* Filled in below if boost is enabled */
	NULL,
};

static int apple_soc_cpufreq_init(struct cpufreq_policy *policy)
{
	int ret, i;
	unsigned int transition_latency;
	void __iomem *reg_base;
	struct device *cpu_dev;
	struct apple_cpu_priv *priv;
	const struct apple_soc_cpufreq_info *info;
	struct cpufreq_frequency_table *freq_table;

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

	ret = dev_pm_opp_of_add_table(cpu_dev);
	if (ret < 0) {
		dev_err(cpu_dev, "%s: failed to add OPP table: %d\n", __func__, ret);
		return ret;
	}

	ret = apple_soc_cpufreq_find_cluster(policy, &reg_base, &info);
	if (ret) {
		dev_err(cpu_dev, "%s: failed to get cluster info: %d\n", __func__, ret);
		return ret;
	}

	ret = dev_pm_opp_set_sharing_cpus(cpu_dev, policy->cpus);
	if (ret) {
		dev_err(cpu_dev, "%s: failed to mark OPPs as shared: %d\n", __func__, ret);
		goto out_iounmap;
	}

	ret = dev_pm_opp_get_opp_count(cpu_dev);
	if (ret <= 0) {
		dev_dbg(cpu_dev, "OPP table is not ready, deferring probe\n");
		ret = -EPROBE_DEFER;
		goto out_free_opp;
	}

	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
	if (!priv) {
		ret = -ENOMEM;
		goto out_free_opp;
	}

	ret = dev_pm_opp_init_cpufreq_table(cpu_dev, &freq_table);
	if (ret) {
		dev_err(cpu_dev, "failed to init cpufreq table: %d\n", ret);
		goto out_free_priv;
	}

	/* Get OPP levels (p-state indexes) and stash them in driver_data */
	for (i = 0; freq_table[i].frequency != CPUFREQ_TABLE_END; i++) {
		unsigned long rate = freq_table[i].frequency * 1000 + 999;
		struct dev_pm_opp *opp = dev_pm_opp_find_freq_floor(cpu_dev, &rate);

		if (IS_ERR(opp)) {
			ret = PTR_ERR(opp);
			goto out_free_cpufreq_table;
		}
		freq_table[i].driver_data = dev_pm_opp_get_level(opp);
		dev_pm_opp_put(opp);
	}

	priv->cpu_dev = cpu_dev;
	priv->reg_base = reg_base;
	priv->info = info;
	policy->driver_data = priv;
	policy->freq_table = freq_table;

	transition_latency = dev_pm_opp_get_max_transition_latency(cpu_dev);
	if (!transition_latency)
		transition_latency = CPUFREQ_ETERNAL;

	policy->cpuinfo.transition_latency = transition_latency;
	policy->dvfs_possible_from_any_cpu = true;
	policy->fast_switch_possible = true;
	policy->suspend_freq = freq_table[0].frequency;

	if (policy_has_boost_freq(policy)) {
		ret = cpufreq_enable_boost_support();
		if (ret) {
			dev_warn(cpu_dev, "failed to enable boost: %d\n", ret);
		} else {
			apple_soc_cpufreq_hw_attr[1] = &cpufreq_freq_attr_scaling_boost_freqs;
			apple_soc_cpufreq_driver.boost_enabled = true;
		}
	}

	return 0;

out_free_cpufreq_table:
	dev_pm_opp_free_cpufreq_table(cpu_dev, &freq_table);
out_free_priv:
	kfree(priv);
out_free_opp:
	dev_pm_opp_remove_all_dynamic(cpu_dev);
out_iounmap:
	iounmap(reg_base);
	return ret;
}

static void apple_soc_cpufreq_exit(struct cpufreq_policy *policy)
{
	struct apple_cpu_priv *priv = policy->driver_data;

	dev_pm_opp_free_cpufreq_table(priv->cpu_dev, &policy->freq_table);
	dev_pm_opp_remove_all_dynamic(priv->cpu_dev);
	iounmap(priv->reg_base);
	kfree(priv);
}

static struct cpufreq_driver apple_soc_cpufreq_driver = {
	.name		= "apple-cpufreq",
	.flags		= CPUFREQ_HAVE_GOVERNOR_PER_POLICY |
			  CPUFREQ_NEED_INITIAL_FREQ_CHECK | CPUFREQ_IS_COOLING_DEV,
	.verify		= cpufreq_generic_frequency_table_verify,
	.get		= apple_soc_cpufreq_get_rate,
	.init		= apple_soc_cpufreq_init,
	.exit		= apple_soc_cpufreq_exit,
	.target_index	= apple_soc_cpufreq_set_target,
	.fast_switch	= apple_soc_cpufreq_fast_switch,
	.register_em	= cpufreq_register_em_with_opp,
	.attr		= apple_soc_cpufreq_hw_attr,
	.suspend	= cpufreq_generic_suspend,
};

static int __init apple_soc_cpufreq_module_init(void)
{
	if (!of_machine_is_compatible("apple,arm-platform"))
		return -ENODEV;

	return cpufreq_register_driver(&apple_soc_cpufreq_driver);
}
module_init(apple_soc_cpufreq_module_init);

static void __exit apple_soc_cpufreq_module_exit(void)
{
	cpufreq_unregister_driver(&apple_soc_cpufreq_driver);
}
module_exit(apple_soc_cpufreq_module_exit);

MODULE_DEVICE_TABLE(of, apple_soc_cpufreq_of_match);
MODULE_AUTHOR("Hector Martin <marcan@marcan.st>");
MODULE_DESCRIPTION("Apple SoC CPU cluster DVFS driver");
MODULE_LICENSE("GPL");