kernel/drivers/cpuidle/dt_idle_states.c

   1 /*
   2  * DT idle states parsing code.
   3  *
   4  * Copyright (C) 2014 ARM Ltd.
   5  * Author: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11
  12 #define pr_fmt(fmt) "DT idle-states: " fmt
  13
  14 #include <linux/cpuidle.h>
  15 #include <linux/cpumask.h>
  16 #include <linux/errno.h>
  17 #include <linux/kernel.h>
  18 #include <linux/module.h>
  19 #include <linux/of.h>
  20 #include <linux/of_device.h>
  21
  22 #include "dt_idle_states.h"
  23
  24 static int init_state_node(struct cpuidle_state *idle_state,
  25                            const struct of_device_id *matches,
  26                            struct device_node *state_node)
  27 {
  28         int err;
  29         const struct of_device_id *match_id;
  30         const char *desc;
  31
  32         match_id = of_match_node(matches, state_node);
  33         if (!match_id)
  34                 return -ENODEV;
  35         /*
  36          * CPUidle drivers are expected to initialize the const void *data
  37          * pointer of the passed in struct of_device_id array to the idle
  38          * state enter function.
  39          */
  40         idle_state->enter = match_id->data;
  41
  42         err = of_property_read_u32(state_node, "wakeup-latency-us",
  43                                    &idle_state->exit_latency);
  44         if (err) {
  45                 u32 entry_latency, exit_latency;
  46
  47                 err = of_property_read_u32(state_node, "entry-latency-us",
  48                                            &entry_latency);
  49                 if (err) {
  50                         pr_debug(" * %s missing entry-latency-us property\n",
  51                                  state_node->full_name);
  52                         return -EINVAL;
  53                 }
  54
  55                 err = of_property_read_u32(state_node, "exit-latency-us",
  56                                            &exit_latency);
  57                 if (err) {
  58                         pr_debug(" * %s missing exit-latency-us property\n",
  59                                  state_node->full_name);
  60                         return -EINVAL;
  61                 }
  62                 /*
  63                  * If wakeup-latency-us is missing, default to entry+exit
  64                  * latencies as defined in idle states bindings
  65                  */
  66                 idle_state->exit_latency = entry_latency + exit_latency;
  67         }
  68
  69         err = of_property_read_u32(state_node, "min-residency-us",
  70                                    &idle_state->target_residency);
  71         if (err) {
  72                 pr_debug(" * %s missing min-residency-us property\n",
  73                              state_node->full_name);
  74                 return -EINVAL;
  75         }
  76
  77         err = of_property_read_string(state_node, "idle-state-name", &desc);
  78         if (err)
  79                 desc = state_node->name;
  80
  81         idle_state->flags = 0;
  82         if (of_property_read_bool(state_node, "local-timer-stop"))
  83                 idle_state->flags |= CPUIDLE_FLAG_TIMER_STOP;
  84         /*
  85          * TODO:
  86          *      replace with kstrdup and pointer assignment when name
  87          *      and desc become string pointers
  88          */
  89         strncpy(idle_state->name, state_node->name, CPUIDLE_NAME_LEN - 1);
  90         strncpy(idle_state->desc, desc, CPUIDLE_DESC_LEN - 1);
  91         return 0;
  92 }
  93
  94 /*
  95  * Check that the idle state is uniform across all CPUs in the CPUidle driver
  96  * cpumask
  97  */
  98 static bool idle_state_valid(struct device_node *state_node, unsigned int idx,
  99                              const cpumask_t *cpumask)
 100 {
 101         int cpu;
 102         struct device_node *cpu_node, *curr_state_node;
 103         bool valid = true;
 104
 105         /*
 106          * Compare idle state phandles for index idx on all CPUs in the
 107          * CPUidle driver cpumask. Start from next logical cpu following
 108          * cpumask_first(cpumask) since that's the CPU state_node was
 109          * retrieved from. If a mismatch is found bail out straight
 110          * away since we certainly hit a firmware misconfiguration.
 111          */
 112         for (cpu = cpumask_next(cpumask_first(cpumask), cpumask);
 113              cpu < nr_cpu_ids; cpu = cpumask_next(cpu, cpumask)) {
 114                 cpu_node = of_cpu_device_node_get(cpu);
 115                 curr_state_node = of_parse_phandle(cpu_node, "cpu-idle-states",
 116                                                    idx);
 117                 if (state_node != curr_state_node)
 118                         valid = false;
 119
 120                 of_node_put(curr_state_node);
 121                 of_node_put(cpu_node);
 122                 if (!valid)
 123                         break;
 124         }
 125
 126         return valid;
 127 }
 128
 129 /**
 130  * dt_init_idle_driver() - Parse the DT idle states and initialize the
 131  *                         idle driver states array
 132  * @drv:          Pointer to CPU idle driver to be initialized
 133  * @matches:      Array of of_device_id match structures to search in for
 134  *                compatible idle state nodes. The data pointer for each valid
 135  *                struct of_device_id entry in the matches array must point to
 136  *                a function with the following signature, that corresponds to
 137  *                the CPUidle state enter function signature:
 138  *
 139  *                int (*)(struct cpuidle_device *dev,
 140  *                        struct cpuidle_driver *drv,
 141  *                        int index);
 142  *
 143  * @start_idx:    First idle state index to be initialized
 144  *
 145  * If DT idle states are detected and are valid the state count and states
 146  * array entries in the cpuidle driver are initialized accordingly starting
 147  * from index start_idx.
 148  *
 149  * Return: number of valid DT idle states parsed, <0 on failure
 150  */
 151 int dt_init_idle_driver(struct cpuidle_driver *drv,
 152                         const struct of_device_id *matches,
 153                         unsigned int start_idx)
 154 {
 155         struct cpuidle_state *idle_state;
 156         struct device_node *state_node, *cpu_node;
 157         int i, err = 0;
 158         const cpumask_t *cpumask;
 159         unsigned int state_idx = start_idx;
 160
 161         if (state_idx >= CPUIDLE_STATE_MAX)
 162                 return -EINVAL;
 163         /*
 164          * We get the idle states for the first logical cpu in the
 165          * driver mask (or cpu_possible_mask if the driver cpumask is not set)
 166          * and we check through idle_state_valid() if they are uniform
 167          * across CPUs, otherwise we hit a firmware misconfiguration.
 168          */
 169         cpumask = drv->cpumask ? : cpu_possible_mask;
 170         cpu_node = of_cpu_device_node_get(cpumask_first(cpumask));
 171
 172         for (i = 0; ; i++) {
 173                 state_node = of_parse_phandle(cpu_node, "cpu-idle-states", i);
 174                 if (!state_node)
 175                         break;
 176
 177                 if (!of_device_is_available(state_node))
 178                         continue;
 179
 180                 if (!idle_state_valid(state_node, i, cpumask)) {
 181                         pr_warn("%s idle state not valid, bailing out\n",
 182                                 state_node->full_name);
 183                         err = -EINVAL;
 184                         break;
 185                 }
 186
 187                 if (state_idx == CPUIDLE_STATE_MAX) {
 188                         pr_warn("State index reached static CPU idle driver states array size\n");
 189                         break;
 190                 }
 191
 192                 idle_state = &drv->states[state_idx++];
 193                 err = init_state_node(idle_state, matches, state_node);
 194                 if (err) {
 195                         pr_err("Parsing idle state node %s failed with err %d\n",
 196                                state_node->full_name, err);
 197                         err = -EINVAL;
 198                         break;
 199                 }
 200                 of_node_put(state_node);
 201         }
 202
 203         of_node_put(state_node);
 204         of_node_put(cpu_node);
 205         if (err)
 206                 return err;
 207         /*
 208          * Update the driver state count only if some valid DT idle states
 209          * were detected
 210          */
 211         if (i)
 212                 drv->state_count = state_idx;
 213
 214         /*
 215          * Return the number of present and valid DT idle states, which can
 216          * also be 0 on platforms with missing DT idle states or legacy DT
 217          * configuration predating the DT idle states bindings.
 218          */
 219         return i;
 220 }
 221 EXPORT_SYMBOL_GPL(dt_init_idle_driver);