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