drivers/cpufreq/ppc_cbe_cpufreq.c

   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>");