drivers/cpufreq/sfi-cpufreq.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  SFI Performance States Driver
   4  *
   5  *  Author: Vishwesh M Rudramuni <vishwesh.m.rudramuni@intel.com>
   6  *  Author: Srinidhi Kasagar <srinidhi.kasagar@intel.com>
   7  */
   8
   9 #include <linux/cpufreq.h>
  10 #include <linux/init.h>
  11 #include <linux/kernel.h>
  12 #include <linux/module.h>
  13 #include <linux/sfi.h>
  14 #include <linux/slab.h>
  15 #include <linux/smp.h>
  16
  17 #include <asm/msr.h>
  18
  19 static struct cpufreq_frequency_table *freq_table;
  20 static struct sfi_freq_table_entry *sfi_cpufreq_array;
  21 static int num_freq_table_entries;
  22
  23 static int sfi_parse_freq(struct sfi_table_header *table)
  24 {
  25         struct sfi_table_simple *sb;
  26         struct sfi_freq_table_entry *pentry;
  27         int totallen;
  28
  29         sb = (struct sfi_table_simple *)table;
  30         num_freq_table_entries = SFI_GET_NUM_ENTRIES(sb,
  31                         struct sfi_freq_table_entry);
  32         if (num_freq_table_entries <= 1) {
  33                 pr_err("No p-states discovered\n");
  34                 return -ENODEV;
  35         }
  36
  37         pentry = (struct sfi_freq_table_entry *)sb->pentry;
  38         totallen = num_freq_table_entries * sizeof(*pentry);
  39
  40         sfi_cpufreq_array = kmemdup(pentry, totallen, GFP_KERNEL);
  41         if (!sfi_cpufreq_array)
  42                 return -ENOMEM;
  43
  44         return 0;
  45 }
  46
  47 static int sfi_cpufreq_target(struct cpufreq_policy *policy, unsigned int index)
  48 {
  49         unsigned int next_perf_state = 0; /* Index into perf table */
  50         u32 lo, hi;
  51
  52         next_perf_state = policy->freq_table[index].driver_data;
  53
  54         rdmsr_on_cpu(policy->cpu, MSR_IA32_PERF_CTL, &lo, &hi);
  55         lo = (lo & ~INTEL_PERF_CTL_MASK) |
  56                 ((u32) sfi_cpufreq_array[next_perf_state].ctrl_val &
  57                 INTEL_PERF_CTL_MASK);
  58         wrmsr_on_cpu(policy->cpu, MSR_IA32_PERF_CTL, lo, hi);
  59
  60         return 0;
  61 }
  62
  63 static int sfi_cpufreq_cpu_init(struct cpufreq_policy *policy)
  64 {
  65         policy->shared_type = CPUFREQ_SHARED_TYPE_HW;
  66         policy->cpuinfo.transition_latency = 100000;    /* 100us */
  67         policy->freq_table = freq_table;
  68
  69         return 0;
  70 }
  71
  72 static struct cpufreq_driver sfi_cpufreq_driver = {
  73         .flags          = CPUFREQ_CONST_LOOPS,
  74         .verify         = cpufreq_generic_frequency_table_verify,
  75         .target_index   = sfi_cpufreq_target,
  76         .init           = sfi_cpufreq_cpu_init,
  77         .name           = "sfi-cpufreq",
  78         .attr           = cpufreq_generic_attr,
  79 };
  80
  81 static int __init sfi_cpufreq_init(void)
  82 {
  83         int ret, i;
  84
  85         /* parse the freq table from SFI */
  86         ret = sfi_table_parse(SFI_SIG_FREQ, NULL, NULL, sfi_parse_freq);
  87         if (ret)
  88                 return ret;
  89
  90         freq_table = kcalloc(num_freq_table_entries + 1, sizeof(*freq_table),
  91                              GFP_KERNEL);
  92         if (!freq_table) {
  93                 ret = -ENOMEM;
  94                 goto err_free_array;
  95         }
  96
  97         for (i = 0; i < num_freq_table_entries; i++) {
  98                 freq_table[i].driver_data = i;
  99                 freq_table[i].frequency = sfi_cpufreq_array[i].freq_mhz * 1000;
 100         }
 101         freq_table[i].frequency = CPUFREQ_TABLE_END;
 102
 103         ret = cpufreq_register_driver(&sfi_cpufreq_driver);
 104         if (ret)
 105                 goto err_free_tbl;
 106
 107         return ret;
 108
 109 err_free_tbl:
 110         kfree(freq_table);
 111 err_free_array:
 112         kfree(sfi_cpufreq_array);
 113         return ret;
 114 }
 115 late_initcall(sfi_cpufreq_init);
 116
 117 static void __exit sfi_cpufreq_exit(void)
 118 {
 119         cpufreq_unregister_driver(&sfi_cpufreq_driver);
 120         kfree(freq_table);
 121         kfree(sfi_cpufreq_array);
 122 }
 123 module_exit(sfi_cpufreq_exit);
 124
 125 MODULE_AUTHOR("Vishwesh M Rudramuni <vishwesh.m.rudramuni@intel.com>");
 126 MODULE_DESCRIPTION("SFI Performance-States Driver");
 127 MODULE_LICENSE("GPL");