path: root/drivers/cpufreq/sun50i-cpufreq-nvmem.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Allwinner CPUFreq nvmem based driver
 *
 * The sun50i-cpufreq-nvmem driver reads the efuse value from the SoC to
 * provide the OPP framework with required information.
 *
 * Copyright (C) 2019 Yangtao Li <tiny.windzz@gmail.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/cpu.h>
#include <linux/module.h>
#include <linux/nvmem-consumer.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pm_opp.h>
#include <linux/slab.h>

#define MAX_NAME_LEN	7

#define NVMEM_MASK	0x7
#define NVMEM_SHIFT	5

static struct platform_device *cpufreq_dt_pdev, *sun50i_cpufreq_pdev;

struct sunxi_cpufreq_data {
	u32 (*efuse_xlate)(u32 speedbin);
};

static u32 sun50i_h6_efuse_xlate(u32 speedbin)
{
	u32 efuse_value;

	efuse_value = (speedbin >> NVMEM_SHIFT) & NVMEM_MASK;

	/*
	 * We treat unexpected efuse values as if the SoC was from
	 * the slowest bin. Expected efuse values are 1-3, slowest
	 * to fastest.
	 */
	if (efuse_value >= 1 && efuse_value <= 3)
		return efuse_value - 1;
	else
		return 0;
}

static struct sunxi_cpufreq_data sun50i_h6_cpufreq_data = {
	.efuse_xlate = sun50i_h6_efuse_xlate,
};

static const struct of_device_id cpu_opp_match_list[] = {
	{ .compatible = "allwinner,sun50i-h6-operating-points",
	  .data = &sun50i_h6_cpufreq_data,
	},
	{}
};

/**
 * dt_has_supported_hw() - Check if any OPPs use opp-supported-hw
 *
 * If we ask the cpufreq framework to use the opp-supported-hw feature, it
 * will ignore every OPP node without that DT property. If none of the OPPs
 * have it, the driver will fail probing, due to the lack of OPPs.
 *
 * Returns true if we have at least one OPP with the opp-supported-hw property.
 */
static bool dt_has_supported_hw(void)
{
	bool has_opp_supported_hw = false;
	struct device_node *np, *opp;
	struct device *cpu_dev;

	cpu_dev = get_cpu_device(0);
	if (!cpu_dev)
		return -ENODEV;

	np = dev_pm_opp_of_get_opp_desc_node(cpu_dev);
	if (!np)
		return -ENOENT;

	for_each_child_of_node(np, opp) {
		if (of_find_property(opp, "opp-supported-hw", NULL)) {
			has_opp_supported_hw = true;
			break;
		}
	}

	of_node_put(np);

	return has_opp_supported_hw;
}

/**
 * sun50i_cpufreq_get_efuse() - Determine speed grade from efuse value
 *
 * Returns non-negative speed bin index on success, a negative error
 * value otherwise.
 */
static int sun50i_cpufreq_get_efuse(void)
{
	const struct sunxi_cpufreq_data *opp_data;
	struct nvmem_cell *speedbin_nvmem;
	const struct of_device_id *match;
	struct device_node *np;
	struct device *cpu_dev;
	u32 *speedbin;
	int ret;

	cpu_dev = get_cpu_device(0);
	if (!cpu_dev)
		return -ENODEV;

	np = dev_pm_opp_of_get_opp_desc_node(cpu_dev);
	if (!np)
		return -ENOENT;

	match = of_match_node(cpu_opp_match_list, np);
	if (!match) {
		of_node_put(np);
		return -ENOENT;
	}
	opp_data = match->data;

	speedbin_nvmem = of_nvmem_cell_get(np, NULL);
	of_node_put(np);
	if (IS_ERR(speedbin_nvmem))
		return dev_err_probe(cpu_dev, PTR_ERR(speedbin_nvmem),
				     "Could not get nvmem cell\n");

	speedbin = nvmem_cell_read(speedbin_nvmem, NULL);
	nvmem_cell_put(speedbin_nvmem);
	if (IS_ERR(speedbin))
		return PTR_ERR(speedbin);

	ret = opp_data->efuse_xlate(*speedbin);

	kfree(speedbin);

	return ret;
};

static int sun50i_cpufreq_nvmem_probe(struct platform_device *pdev)
{
	int *opp_tokens;
	char name[MAX_NAME_LEN];
	unsigned int cpu, supported_hw;
	struct dev_pm_opp_config config = {};
	int speed;
	int ret;

	opp_tokens = kcalloc(num_possible_cpus(), sizeof(*opp_tokens),
			     GFP_KERNEL);
	if (!opp_tokens)
		return -ENOMEM;

	speed = sun50i_cpufreq_get_efuse();
	if (speed < 0) {
		kfree(opp_tokens);
		return speed;
	}

	/*
	 * We need at least one OPP with the "opp-supported-hw" property,
	 * or else the upper layers will ignore every OPP and will bail out.
	 */
	if (dt_has_supported_hw()) {
		supported_hw = 1U << speed;
		config.supported_hw = &supported_hw;
		config.supported_hw_count = 1;
	}

	snprintf(name, MAX_NAME_LEN, "speed%d", speed);
	config.prop_name = name;

	for_each_possible_cpu(cpu) {
		struct device *cpu_dev = get_cpu_device(cpu);

		if (!cpu_dev) {
			ret = -ENODEV;
			goto free_opp;
		}

		ret = dev_pm_opp_set_config(cpu_dev, &config);
		if (ret < 0)
			goto free_opp;

		opp_tokens[cpu] = ret;
	}

	cpufreq_dt_pdev = platform_device_register_simple("cpufreq-dt", -1,
							  NULL, 0);
	if (!IS_ERR(cpufreq_dt_pdev)) {
		platform_set_drvdata(pdev, opp_tokens);
		return 0;
	}

	ret = PTR_ERR(cpufreq_dt_pdev);
	pr_err("Failed to register platform device\n");

free_opp:
	for_each_possible_cpu(cpu)
		dev_pm_opp_clear_config(opp_tokens[cpu]);
	kfree(opp_tokens);

	return ret;
}

static void sun50i_cpufreq_nvmem_remove(struct platform_device *pdev)
{
	int *opp_tokens = platform_get_drvdata(pdev);
	unsigned int cpu;

	platform_device_unregister(cpufreq_dt_pdev);

	for_each_possible_cpu(cpu)
		dev_pm_opp_clear_config(opp_tokens[cpu]);

	kfree(opp_tokens);
}

static struct platform_driver sun50i_cpufreq_driver = {
	.probe = sun50i_cpufreq_nvmem_probe,
	.remove_new = sun50i_cpufreq_nvmem_remove,
	.driver = {
		.name = "sun50i-cpufreq-nvmem",
	},
};

static const struct of_device_id sun50i_cpufreq_match_list[] = {
	{ .compatible = "allwinner,sun50i-h6" },
	{}
};
MODULE_DEVICE_TABLE(of, sun50i_cpufreq_match_list);

static const struct of_device_id *sun50i_cpufreq_match_node(void)
{
	const struct of_device_id *match;
	struct device_node *np;

	np = of_find_node_by_path("/");
	match = of_match_node(sun50i_cpufreq_match_list, np);
	of_node_put(np);

	return match;
}

/*
 * Since the driver depends on nvmem drivers, which may return EPROBE_DEFER,
 * all the real activity is done in the probe, which may be defered as well.
 * The init here is only registering the driver and the platform device.
 */
static int __init sun50i_cpufreq_init(void)
{
	const struct of_device_id *match;
	int ret;

	match = sun50i_cpufreq_match_node();
	if (!match)
		return -ENODEV;

	ret = platform_driver_register(&sun50i_cpufreq_driver);
	if (unlikely(ret < 0))
		return ret;

	sun50i_cpufreq_pdev =
		platform_device_register_simple("sun50i-cpufreq-nvmem",
						-1, NULL, 0);
	ret = PTR_ERR_OR_ZERO(sun50i_cpufreq_pdev);
	if (ret == 0)
		return 0;

	platform_driver_unregister(&sun50i_cpufreq_driver);
	return ret;
}
module_init(sun50i_cpufreq_init);

static void __exit sun50i_cpufreq_exit(void)
{
	platform_device_unregister(sun50i_cpufreq_pdev);
	platform_driver_unregister(&sun50i_cpufreq_driver);
}
module_exit(sun50i_cpufreq_exit);

MODULE_DESCRIPTION("Sun50i-h6 cpufreq driver");
MODULE_LICENSE("GPL v2");