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          * Since this is not a "coupled" state, it's safe to assume interrupts
  43          * won't be enabled when it exits allowing the tick to be frozen
  44          * safely. So enter() can be also enter_freeze() callback.
  45          */
  46         idle_state->enter_freeze = match_id->data;
  47
  48         err = of_property_read_u32(state_node, "wakeup-latency-us",
  49                                    &idle_state->exit_latency);
  50         if (err) {
  51                 u32 entry_latency, exit_latency;
  52
  53                 err = of_property_read_u32(state_node, "entry-latency-us",
  54                                            &entry_latency);
  55                 if (err) {
  56                         pr_debug(" * %s missing entry-latency-us property\n",
  57                                  state_node->full_name);
  58                         return -EINVAL;
  59                 }
  60
  61                 err = of_property_read_u32(state_node, "exit-latency-us",
  62                                            &exit_latency);
  63                 if (err) {
  64                         pr_debug(" * %s missing exit-latency-us property\n",
  65                                  state_node->full_name);
  66                         return -EINVAL;
  67                 }
  68                 /*
  69                  * If wakeup-latency-us is missing, default to entry+exit
  70                  * latencies as defined in idle states bindings
  71                  */
  72                 idle_state->exit_latency = entry_latency + exit_latency;
  73         }
  74
  75         err = of_property_read_u32(state_node, "min-residency-us",
  76                                    &idle_state->target_residency);
  77         if (err) {
  78                 pr_debug(" * %s missing min-residency-us property\n",
  79                              state_node->full_name);
  80                 return -EINVAL;
  81         }
  82
  83         err = of_property_read_string(state_node, "idle-state-name", &desc);
  84         if (err)
  85                 desc = state_node->name;
  86
  87         idle_state->flags = 0;
  88         if (of_property_read_bool(state_node, "local-timer-stop"))
  89                 idle_state->flags |= CPUIDLE_FLAG_TIMER_STOP;
  90         /*
  91          * TODO:
  92          *      replace with kstrdup and pointer assignment when name
  93          *      and desc become string pointers
  94          */
  95         strncpy(idle_state->name, state_node->name, CPUIDLE_NAME_LEN - 1);
  96         strncpy(idle_state->desc, desc, CPUIDLE_DESC_LEN - 1);
  97         return 0;
  98 }
  99
 100 /*
 101  * Check that the idle state is uniform across all CPUs in the CPUidle driver
 102  * cpumask
 103  */
 104 static bool idle_state_valid(struct device_node *state_node, unsigned int idx,
 105                              const cpumask_t *cpumask)
 106 {
 107         int cpu;
 108         struct device_node *cpu_node, *curr_state_node;
 109         bool valid = true;
 110
 111         /*
 112          * Compare idle state phandles for index idx on all CPUs in the
 113          * CPUidle driver cpumask. Start from next logical cpu following
 114          * cpumask_first(cpumask) since that's the CPU state_node was
 115          * retrieved from. If a mismatch is found bail out straight
 116          * away since we certainly hit a firmware misconfiguration.
 117          */
 118         for (cpu = cpumask_next(cpumask_first(cpumask), cpumask);
 119              cpu < nr_cpu_ids; cpu = cpumask_next(cpu, cpumask)) {
 120                 cpu_node = of_cpu_device_node_get(cpu);
 121                 curr_state_node = of_parse_phandle(cpu_node, "cpu-idle-states",
 122                                                    idx);
 123                 if (state_node != curr_state_node)
 124                         valid = false;
 125
 126                 of_node_put(curr_state_node);
 127                 of_node_put(cpu_node);
 128                 if (!valid)
 129                         break;
 130         }
 131
 132         return valid;
 133 }
 134
 135 /**
 136  * dt_init_idle_driver() - Parse the DT idle states and initialize the
 137  *                         idle driver states array
 138  * @drv:          Pointer to CPU idle driver to be initialized
 139  * @matches:      Array of of_device_id match structures to search in for
 140  *                compatible idle state nodes. The data pointer for each valid
 141  *                struct of_device_id entry in the matches array must point to
 142  *                a function with the following signature, that corresponds to
 143  *                the CPUidle state enter function signature:
 144  *
 145  *                int (*)(struct cpuidle_device *dev,
 146  *                        struct cpuidle_driver *drv,
 147  *                        int index);
 148  *
 149  * @start_idx:    First idle state index to be initialized
 150  *
 151  * If DT idle states are detected and are valid the state count and states
 152  * array entries in the cpuidle driver are initialized accordingly starting
 153  * from index start_idx.
 154  *
 155  * Return: number of valid DT idle states parsed, <0 on failure
 156  */
 157 int dt_init_idle_driver(struct cpuidle_driver *drv,
 158                         const struct of_device_id *matches,
 159                         unsigned int start_idx)
 160 {
 161         struct cpuidle_state *idle_state;
 162         struct device_node *state_node, *cpu_node;
 163         int i, err = 0;
 164         const cpumask_t *cpumask;
 165         unsigned int state_idx = start_idx;
 166
 167         if (state_idx >= CPUIDLE_STATE_MAX)
 168                 return -EINVAL;
 169         /*
 170          * We get the idle states for the first logical cpu in the
 171          * driver mask (or cpu_possible_mask if the driver cpumask is not set)
 172          * and we check through idle_state_valid() if they are uniform
 173          * across CPUs, otherwise we hit a firmware misconfiguration.
 174          */
 175         cpumask = drv->cpumask ? : cpu_possible_mask;
 176         cpu_node = of_cpu_device_node_get(cpumask_first(cpumask));
 177
 178         for (i = 0; ; i++) {
 179                 state_node = of_parse_phandle(cpu_node, "cpu-idle-states", i);
 180                 if (!state_node)
 181                         break;
 182
 183                 if (!of_device_is_available(state_node)) {
 184                         of_node_put(state_node);
 185                         continue;
 186                 }
 187
 188                 if (!idle_state_valid(state_node, i, cpumask)) {
 189                         pr_warn("%s idle state not valid, bailing out\n",
 190                                 state_node->full_name);
 191                         err = -EINVAL;
 192                         break;
 193                 }
 194
 195                 if (state_idx == CPUIDLE_STATE_MAX) {
 196                         pr_warn("State index reached static CPU idle driver states array size\n");
 197                         break;
 198                 }
 199
 200                 idle_state = &drv->states[state_idx++];
 201                 err = init_state_node(idle_state, matches, state_node);
 202                 if (err) {
 203                         pr_err("Parsing idle state node %s failed with err %d\n",
 204                                state_node->full_name, err);
 205                         err = -EINVAL;
 206                         break;
 207                 }
 208                 of_node_put(state_node);
 209         }
 210
 211         of_node_put(state_node);
 212         of_node_put(cpu_node);
 213         if (err)
 214                 return err;
 215         /*
 216          * Update the driver state count only if some valid DT idle states
 217          * were detected
 218          */
 219         if (i)
 220                 drv->state_count = state_idx;
 221
 222         /*
 223          * Return the number of present and valid DT idle states, which can
 224          * also be 0 on platforms with missing DT idle states or legacy DT
 225          * configuration predating the DT idle states bindings.
 226          */
 227         return i;
 228 }
 229 EXPORT_SYMBOL_GPL(dt_init_idle_driver);