1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Allwinner CPUFreq nvmem based driver
4 *
5 * The sun50i-cpufreq-nvmem driver reads the efuse value from the SoC to
6 * provide the OPP framework with required information.
7 *
8 * Copyright (C) 2019 Yangtao Li <tiny.windzz@gmail.com>
9 */
10
11#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12
13#include <linux/cpu.h>
14#include <linux/module.h>
15#include <linux/nvmem-consumer.h>
16#include <linux/of.h>
17#include <linux/platform_device.h>
18#include <linux/pm_opp.h>
19#include <linux/slab.h>
20
21#define MAX_NAME_LEN	7
22
23#define NVMEM_MASK	0x7
24#define NVMEM_SHIFT	5
25
26static struct platform_device *cpufreq_dt_pdev, *sun50i_cpufreq_pdev;
27
28/**
29 * sun50i_cpufreq_get_efuse() - Determine speed grade from efuse value
30 * @versions: Set to the value parsed from efuse
31 *
32 * Returns 0 if success.
33 */
34static int sun50i_cpufreq_get_efuse(u32 *versions)
35{
36	struct nvmem_cell *speedbin_nvmem;
37	struct device_node *np;
38	struct device *cpu_dev;
39	u32 *speedbin, efuse_value;
40	size_t len;
41	int ret;
42
43	cpu_dev = get_cpu_device(0);
44	if (!cpu_dev)
45		return -ENODEV;
46
47	np = dev_pm_opp_of_get_opp_desc_node(cpu_dev);
48	if (!np)
49		return -ENOENT;
50
51	ret = of_device_is_compatible(np,
52				      "allwinner,sun50i-h6-operating-points");
53	if (!ret) {
54		of_node_put(np);
55		return -ENOENT;
56	}
57
58	speedbin_nvmem = of_nvmem_cell_get(np, NULL);
59	of_node_put(np);
60	if (IS_ERR(speedbin_nvmem))
61		return dev_err_probe(cpu_dev, PTR_ERR(speedbin_nvmem),
62				     "Could not get nvmem cell\n");
63
64	speedbin = nvmem_cell_read(speedbin_nvmem, &len);
65	nvmem_cell_put(speedbin_nvmem);
66	if (IS_ERR(speedbin))
67		return PTR_ERR(speedbin);
68
69	efuse_value = (*speedbin >> NVMEM_SHIFT) & NVMEM_MASK;
70
71	/*
72	 * We treat unexpected efuse values as if the SoC was from
73	 * the slowest bin. Expected efuse values are 1-3, slowest
74	 * to fastest.
75	 */
76	if (efuse_value >= 1 && efuse_value <= 3)
77		*versions = efuse_value - 1;
78	else
79		*versions = 0;
80
81	kfree(speedbin);
82	return 0;
83};
84
85static int sun50i_cpufreq_nvmem_probe(struct platform_device *pdev)
86{
87	int *opp_tokens;
88	char name[MAX_NAME_LEN];
89	unsigned int cpu;
90	u32 speed = 0;
91	int ret;
92
93	opp_tokens = kcalloc(num_possible_cpus(), sizeof(*opp_tokens),
94			     GFP_KERNEL);
95	if (!opp_tokens)
96		return -ENOMEM;
97
98	ret = sun50i_cpufreq_get_efuse(&speed);
99	if (ret) {
100		kfree(opp_tokens);
101		return ret;
102	}
103
104	snprintf(name, MAX_NAME_LEN, "speed%d", speed);
105
106	for_each_possible_cpu(cpu) {
107		struct device *cpu_dev = get_cpu_device(cpu);
108
109		if (!cpu_dev) {
110			ret = -ENODEV;
111			goto free_opp;
112		}
113
114		opp_tokens[cpu] = dev_pm_opp_set_prop_name(cpu_dev, name);
115		if (opp_tokens[cpu] < 0) {
116			ret = opp_tokens[cpu];
117			pr_err("Failed to set prop name\n");
118			goto free_opp;
119		}
120	}
121
122	cpufreq_dt_pdev = platform_device_register_simple("cpufreq-dt", -1,
123							  NULL, 0);
124	if (!IS_ERR(cpufreq_dt_pdev)) {
125		platform_set_drvdata(pdev, opp_tokens);
126		return 0;
127	}
128
129	ret = PTR_ERR(cpufreq_dt_pdev);
130	pr_err("Failed to register platform device\n");
131
132free_opp:
133	for_each_possible_cpu(cpu)
134		dev_pm_opp_put_prop_name(opp_tokens[cpu]);
135	kfree(opp_tokens);
136
137	return ret;
138}
139
140static void sun50i_cpufreq_nvmem_remove(struct platform_device *pdev)
141{
142	int *opp_tokens = platform_get_drvdata(pdev);
143	unsigned int cpu;
144
145	platform_device_unregister(cpufreq_dt_pdev);
146
147	for_each_possible_cpu(cpu)
148		dev_pm_opp_put_prop_name(opp_tokens[cpu]);
149
150	kfree(opp_tokens);
151}
152
153static struct platform_driver sun50i_cpufreq_driver = {
154	.probe = sun50i_cpufreq_nvmem_probe,
155	.remove_new = sun50i_cpufreq_nvmem_remove,
156	.driver = {
157		.name = "sun50i-cpufreq-nvmem",
158	},
159};
160
161static const struct of_device_id sun50i_cpufreq_match_list[] = {
162	{ .compatible = "allwinner,sun50i-h6" },
163	{}
164};
165MODULE_DEVICE_TABLE(of, sun50i_cpufreq_match_list);
166
167static const struct of_device_id *sun50i_cpufreq_match_node(void)
168{
169	const struct of_device_id *match;
170	struct device_node *np;
171
172	np = of_find_node_by_path("/");
173	match = of_match_node(sun50i_cpufreq_match_list, np);
174	of_node_put(np);
175
176	return match;
177}
178
179/*
180 * Since the driver depends on nvmem drivers, which may return EPROBE_DEFER,
181 * all the real activity is done in the probe, which may be defered as well.
182 * The init here is only registering the driver and the platform device.
183 */
184static int __init sun50i_cpufreq_init(void)
185{
186	const struct of_device_id *match;
187	int ret;
188
189	match = sun50i_cpufreq_match_node();
190	if (!match)
191		return -ENODEV;
192
193	ret = platform_driver_register(&sun50i_cpufreq_driver);
194	if (unlikely(ret < 0))
195		return ret;
196
197	sun50i_cpufreq_pdev =
198		platform_device_register_simple("sun50i-cpufreq-nvmem",
199						-1, NULL, 0);
200	ret = PTR_ERR_OR_ZERO(sun50i_cpufreq_pdev);
201	if (ret == 0)
202		return 0;
203
204	platform_driver_unregister(&sun50i_cpufreq_driver);
205	return ret;
206}
207module_init(sun50i_cpufreq_init);
208
209static void __exit sun50i_cpufreq_exit(void)
210{
211	platform_device_unregister(sun50i_cpufreq_pdev);
212	platform_driver_unregister(&sun50i_cpufreq_driver);
213}
214module_exit(sun50i_cpufreq_exit);
215
216MODULE_DESCRIPTION("Sun50i-h6 cpufreq driver");
217MODULE_LICENSE("GPL v2");
218