1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * cpufreq driver for the cell processor
4  *
5  * (C) Copyright IBM Deutschland Entwicklung GmbH 2005-2007
6  *
7  * Author: Christian Krafft <krafft@de.ibm.com>
8  */
9 
10 #include <linux/cpufreq.h>
11 #include <linux/module.h>
12 #include <linux/of_platform.h>
13 
14 #include <asm/machdep.h>
15 #include <asm/prom.h>
16 #include <asm/cell-regs.h>
17 
18 #include "ppc_cbe_cpufreq.h"
19 
20 /* the CBE supports an 8 step frequency scaling */
21 static struct cpufreq_frequency_table cbe_freqs[] = {
22 	{0, 1,	0},
23 	{0, 2,	0},
24 	{0, 3,	0},
25 	{0, 4,	0},
26 	{0, 5,	0},
27 	{0, 6,	0},
28 	{0, 8,	0},
29 	{0, 10,	0},
30 	{0, 0,	CPUFREQ_TABLE_END},
31 };
32 
33 /*
34  * hardware specific functions
35  */
36 
37 static int set_pmode(unsigned int cpu, unsigned int slow_mode)
38 {
39 	int rc;
40 
41 	if (cbe_cpufreq_has_pmi)
42 		rc = cbe_cpufreq_set_pmode_pmi(cpu, slow_mode);
43 	else
44 		rc = cbe_cpufreq_set_pmode(cpu, slow_mode);
45 
46 	pr_debug("register contains slow mode %d\n", cbe_cpufreq_get_pmode(cpu));
47 
48 	return rc;
49 }
50 
51 /*
52  * cpufreq functions
53  */
54 
55 static int cbe_cpufreq_cpu_init(struct cpufreq_policy *policy)
56 {
57 	struct cpufreq_frequency_table *pos;
58 	const u32 *max_freqp;
59 	u32 max_freq;
60 	int cur_pmode;
61 	struct device_node *cpu;
62 
63 	cpu = of_get_cpu_node(policy->cpu, NULL);
64 
65 	if (!cpu)
66 		return -ENODEV;
67 
68 	pr_debug("init cpufreq on CPU %d\n", policy->cpu);
69 
70 	/*
71 	 * Let's check we can actually get to the CELL regs
72 	 */
73 	if (!cbe_get_cpu_pmd_regs(policy->cpu) ||
74 	    !cbe_get_cpu_mic_tm_regs(policy->cpu)) {
75 		pr_info("invalid CBE regs pointers for cpufreq\n");
76 		of_node_put(cpu);
77 		return -EINVAL;
78 	}
79 
80 	max_freqp = of_get_property(cpu, "clock-frequency", NULL);
81 
82 	of_node_put(cpu);
83 
84 	if (!max_freqp)
85 		return -EINVAL;
86 
87 	/* we need the freq in kHz */
88 	max_freq = *max_freqp / 1000;
89 
90 	pr_debug("max clock-frequency is at %u kHz\n", max_freq);
91 	pr_debug("initializing frequency table\n");
92 
93 	/* initialize frequency table */
94 	cpufreq_for_each_entry(pos, cbe_freqs) {
95 		pos->frequency = max_freq / pos->driver_data;
96 		pr_debug("%d: %d\n", (int)(pos - cbe_freqs), pos->frequency);
97 	}
98 
99 	/* if DEBUG is enabled set_pmode() measures the latency
100 	 * of a transition */
101 	policy->cpuinfo.transition_latency = 25000;
102 
103 	cur_pmode = cbe_cpufreq_get_pmode(policy->cpu);
104 	pr_debug("current pmode is at %d\n",cur_pmode);
105 
106 	policy->cur = cbe_freqs[cur_pmode].frequency;
107 
108 #ifdef CONFIG_SMP
109 	cpumask_copy(policy->cpus, cpu_sibling_mask(policy->cpu));
110 #endif
111 
112 	policy->freq_table = cbe_freqs;
113 	return 0;
114 }
115 
116 static int cbe_cpufreq_target(struct cpufreq_policy *policy,
117 			      unsigned int cbe_pmode_new)
118 {
119 	pr_debug("setting frequency for cpu %d to %d kHz, " \
120 		 "1/%d of max frequency\n",
121 		 policy->cpu,
122 		 cbe_freqs[cbe_pmode_new].frequency,
123 		 cbe_freqs[cbe_pmode_new].driver_data);
124 
125 	return set_pmode(policy->cpu, cbe_pmode_new);
126 }
127 
128 static struct cpufreq_driver cbe_cpufreq_driver = {
129 	.verify		= cpufreq_generic_frequency_table_verify,
130 	.target_index	= cbe_cpufreq_target,
131 	.init		= cbe_cpufreq_cpu_init,
132 	.name		= "cbe-cpufreq",
133 	.flags		= CPUFREQ_CONST_LOOPS,
134 };
135 
136 /*
137  * module init and destoy
138  */
139 
140 static int __init cbe_cpufreq_init(void)
141 {
142 	if (!machine_is(cell))
143 		return -ENODEV;
144 
145 	return cpufreq_register_driver(&cbe_cpufreq_driver);
146 }
147 
148 static void __exit cbe_cpufreq_exit(void)
149 {
150 	cpufreq_unregister_driver(&cbe_cpufreq_driver);
151 }
152 
153 module_init(cbe_cpufreq_init);
154 module_exit(cbe_cpufreq_exit);
155 
156 MODULE_LICENSE("GPL");
157 MODULE_AUTHOR("Christian Krafft <krafft@de.ibm.com>");
158