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.h>
  13
  14 #include <asm/machdep.h>
  15 #include <asm/cell-regs.h>
  16
  17 #include "ppc_cbe_cpufreq.h"
  18
  19 /* the CBE supports an 8 step frequency scaling */
  20 static struct cpufreq_frequency_table cbe_freqs[] = {
  21         {0, 1,  0},
  22         {0, 2,  0},
  23         {0, 3,  0},
  24         {0, 4,  0},
  25         {0, 5,  0},
  26         {0, 6,  0},
  27         {0, 8,  0},
  28         {0, 10, 0},
  29         {0, 0,  CPUFREQ_TABLE_END},
  30 };
  31
  32 /*
  33  * hardware specific functions
  34  */
  35
  36 static int set_pmode(unsigned int cpu, unsigned int slow_mode)
  37 {
  38         int rc;
  39
  40         if (cbe_cpufreq_has_pmi)
  41                 rc = cbe_cpufreq_set_pmode_pmi(cpu, slow_mode);
  42         else
  43                 rc = cbe_cpufreq_set_pmode(cpu, slow_mode);
  44
  45         pr_debug("register contains slow mode %d\n", cbe_cpufreq_get_pmode(cpu));
  46
  47         return rc;
  48 }
  49
  50 /*
  51  * cpufreq functions
  52  */
  53
  54 static int cbe_cpufreq_cpu_init(struct cpufreq_policy *policy)
  55 {
  56         struct cpufreq_frequency_table *pos;
  57         const u32 *max_freqp;
  58         u32 max_freq;
  59         int cur_pmode;
  60         struct device_node *cpu;
  61
  62         cpu = of_get_cpu_node(policy->cpu, NULL);
  63
  64         if (!cpu)
  65                 return -ENODEV;
  66
  67         pr_debug("init cpufreq on CPU %d\n", policy->cpu);
  68
  69         /*
  70          * Let's check we can actually get to the CELL regs
  71          */
  72         if (!cbe_get_cpu_pmd_regs(policy->cpu) ||
  73             !cbe_get_cpu_mic_tm_regs(policy->cpu)) {
  74                 pr_info("invalid CBE regs pointers for cpufreq\n");
  75                 of_node_put(cpu);
  76                 return -EINVAL;
  77         }
  78
  79         max_freqp = of_get_property(cpu, "clock-frequency", NULL);
  80
  81         of_node_put(cpu);
  82
  83         if (!max_freqp)
  84                 return -EINVAL;
  85
  86         /* we need the freq in kHz */
  87         max_freq = *max_freqp / 1000;
  88
  89         pr_debug("max clock-frequency is at %u kHz\n", max_freq);
  90         pr_debug("initializing frequency table\n");
  91
  92         /* initialize frequency table */
  93         cpufreq_for_each_entry(pos, cbe_freqs) {
  94                 pos->frequency = max_freq / pos->driver_data;
  95                 pr_debug("%d: %d\n", (int)(pos - cbe_freqs), pos->frequency);
  96         }
  97
  98         /* if DEBUG is enabled set_pmode() measures the latency
  99          * of a transition */
 100         policy->cpuinfo.transition_latency = 25000;
 101
 102         cur_pmode = cbe_cpufreq_get_pmode(policy->cpu);
 103         pr_debug("current pmode is at %d\n",cur_pmode);
 104
 105         policy->cur = cbe_freqs[cur_pmode].frequency;
 106
 107 #ifdef CONFIG_SMP
 108         cpumask_copy(policy->cpus, cpu_sibling_mask(policy->cpu));
 109 #endif
 110
 111         policy->freq_table = cbe_freqs;
 112         cbe_cpufreq_pmi_policy_init(policy);
 113         return 0;
 114 }
 115
 116 static void cbe_cpufreq_cpu_exit(struct cpufreq_policy *policy)
 117 {
 118         cbe_cpufreq_pmi_policy_exit(policy);
 119 }
 120
 121 static int cbe_cpufreq_target(struct cpufreq_policy *policy,
 122                               unsigned int cbe_pmode_new)
 123 {
 124         pr_debug("setting frequency for cpu %d to %d kHz, " \
 125                  "1/%d of max frequency\n",
 126                  policy->cpu,
 127                  cbe_freqs[cbe_pmode_new].frequency,
 128                  cbe_freqs[cbe_pmode_new].driver_data);
 129
 130         return set_pmode(policy->cpu, cbe_pmode_new);
 131 }
 132
 133 static struct cpufreq_driver cbe_cpufreq_driver = {
 134         .verify         = cpufreq_generic_frequency_table_verify,
 135         .target_index   = cbe_cpufreq_target,
 136         .init           = cbe_cpufreq_cpu_init,
 137         .exit           = cbe_cpufreq_cpu_exit,
 138         .name           = "cbe-cpufreq",
 139         .flags          = CPUFREQ_CONST_LOOPS,
 140 };
 141
 142 /*
 143  * module init and destoy
 144  */
 145
 146 static int __init cbe_cpufreq_init(void)
 147 {
 148         int ret;
 149
 150         if (!machine_is(cell))
 151                 return -ENODEV;
 152
 153         cbe_cpufreq_pmi_init();
 154
 155         ret = cpufreq_register_driver(&cbe_cpufreq_driver);
 156         if (ret)
 157                 cbe_cpufreq_pmi_exit();
 158
 159         return ret;
 160 }
 161
 162 static void __exit cbe_cpufreq_exit(void)
 163 {
 164         cpufreq_unregister_driver(&cbe_cpufreq_driver);
 165         cbe_cpufreq_pmi_exit();
 166 }
 167
 168 module_init(cbe_cpufreq_init);
 169 module_exit(cbe_cpufreq_exit);
 170
 171 MODULE_DESCRIPTION("cpufreq driver for Cell BE processors");
 172 MODULE_LICENSE("GPL");
 173 MODULE_AUTHOR("Christian Krafft <krafft@de.ibm.com>");