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 *match_id,
  26                            struct device_node *state_node)
  27 {
  28         int err;
  29         const char *desc;
  30
  31         /*
  32          * CPUidle drivers are expected to initialize the const void *data
  33          * pointer of the passed in struct of_device_id array to the idle
  34          * state enter function.
  35          */
  36         idle_state->enter = match_id->data;
  37         /*
  38          * Since this is not a "coupled" state, it's safe to assume interrupts
  39          * won't be enabled when it exits allowing the tick to be frozen
  40          * safely. So enter() can be also enter_s2idle() callback.
  41          */
  42         idle_state->enter_s2idle = match_id->data;
  43
  44         err = of_property_read_u32(state_node, "wakeup-latency-us",
  45                                    &idle_state->exit_latency);
  46         if (err) {
  47                 u32 entry_latency, exit_latency;
  48
  49                 err = of_property_read_u32(state_node, "entry-latency-us",
  50                                            &entry_latency);
  51                 if (err) {
  52                         pr_debug(" * %pOF missing entry-latency-us property\n",
  53                                  state_node);
  54                         return -EINVAL;
  55                 }
  56
  57                 err = of_property_read_u32(state_node, "exit-latency-us",
  58                                            &exit_latency);
  59                 if (err) {
  60                         pr_debug(" * %pOF missing exit-latency-us property\n",
  61                                  state_node);
  62                         return -EINVAL;
  63                 }
  64                 /*
  65                  * If wakeup-latency-us is missing, default to entry+exit
  66                  * latencies as defined in idle states bindings
  67                  */
  68                 idle_state->exit_latency = entry_latency + exit_latency;
  69         }
  70
  71         err = of_property_read_u32(state_node, "min-residency-us",
  72                                    &idle_state->target_residency);
  73         if (err) {
  74                 pr_debug(" * %pOF missing min-residency-us property\n",
  75                              state_node);
  76                 return -EINVAL;
  77         }
  78
  79         err = of_property_read_string(state_node, "idle-state-name", &desc);
  80         if (err)
  81                 desc = state_node->name;
  82
  83         idle_state->flags = 0;
  84         if (of_property_read_bool(state_node, "local-timer-stop"))
  85                 idle_state->flags |= CPUIDLE_FLAG_TIMER_STOP;
  86         /*
  87          * TODO:
  88          *      replace with kstrdup and pointer assignment when name
  89          *      and desc become string pointers
  90          */
  91         strncpy(idle_state->name, state_node->name, CPUIDLE_NAME_LEN - 1);
  92         strncpy(idle_state->desc, desc, CPUIDLE_DESC_LEN - 1);
  93         return 0;
  94 }
  95
  96 /*
  97  * Check that the idle state is uniform across all CPUs in the CPUidle driver
  98  * cpumask
  99  */
 100 static bool idle_state_valid(struct device_node *state_node, unsigned int idx,
 101                              const cpumask_t *cpumask)
 102 {
 103         int cpu;
 104         struct device_node *cpu_node, *curr_state_node;
 105         bool valid = true;
 106
 107         /*
 108          * Compare idle state phandles for index idx on all CPUs in the
 109          * CPUidle driver cpumask. Start from next logical cpu following
 110          * cpumask_first(cpumask) since that's the CPU state_node was
 111          * retrieved from. If a mismatch is found bail out straight
 112          * away since we certainly hit a firmware misconfiguration.
 113          */
 114         for (cpu = cpumask_next(cpumask_first(cpumask), cpumask);
 115              cpu < nr_cpu_ids; cpu = cpumask_next(cpu, cpumask)) {
 116                 cpu_node = of_cpu_device_node_get(cpu);
 117                 curr_state_node = of_parse_phandle(cpu_node, "cpu-idle-states",
 118                                                    idx);
 119                 if (state_node != curr_state_node)
 120                         valid = false;
 121
 122                 of_node_put(curr_state_node);
 123                 of_node_put(cpu_node);
 124                 if (!valid)
 125                         break;
 126         }
 127
 128         return valid;
 129 }
 130
 131 /**
 132  * dt_init_idle_driver() - Parse the DT idle states and initialize the
 133  *                         idle driver states array
 134  * @drv:          Pointer to CPU idle driver to be initialized
 135  * @matches:      Array of of_device_id match structures to search in for
 136  *                compatible idle state nodes. The data pointer for each valid
 137  *                struct of_device_id entry in the matches array must point to
 138  *                a function with the following signature, that corresponds to
 139  *                the CPUidle state enter function signature:
 140  *
 141  *                int (*)(struct cpuidle_device *dev,
 142  *                        struct cpuidle_driver *drv,
 143  *                        int index);
 144  *
 145  * @start_idx:    First idle state index to be initialized
 146  *
 147  * If DT idle states are detected and are valid the state count and states
 148  * array entries in the cpuidle driver are initialized accordingly starting
 149  * from index start_idx.
 150  *
 151  * Return: number of valid DT idle states parsed, <0 on failure
 152  */
 153 int dt_init_idle_driver(struct cpuidle_driver *drv,
 154                         const struct of_device_id *matches,
 155                         unsigned int start_idx)
 156 {
 157         struct cpuidle_state *idle_state;
 158         struct device_node *state_node, *cpu_node;
 159         const struct of_device_id *match_id;
 160         int i, err = 0;
 161         const cpumask_t *cpumask;
 162         unsigned int state_idx = start_idx;
 163
 164         if (state_idx >= CPUIDLE_STATE_MAX)
 165                 return -EINVAL;
 166         /*
 167          * We get the idle states for the first logical cpu in the
 168          * driver mask (or cpu_possible_mask if the driver cpumask is not set)
 169          * and we check through idle_state_valid() if they are uniform
 170          * across CPUs, otherwise we hit a firmware misconfiguration.
 171          */
 172         cpumask = drv->cpumask ? : cpu_possible_mask;
 173         cpu_node = of_cpu_device_node_get(cpumask_first(cpumask));
 174
 175         for (i = 0; ; i++) {
 176                 state_node = of_parse_phandle(cpu_node, "cpu-idle-states", i);
 177                 if (!state_node)
 178                         break;
 179
 180                 match_id = of_match_node(matches, state_node);
 181                 if (!match_id) {
 182                         err = -ENODEV;
 183                         break;
 184                 }
 185
 186                 if (!of_device_is_available(state_node)) {
 187                         of_node_put(state_node);
 188                         continue;
 189                 }
 190
 191                 if (!idle_state_valid(state_node, i, cpumask)) {
 192                         pr_warn("%pOF idle state not valid, bailing out\n",
 193                                 state_node);
 194                         err = -EINVAL;
 195                         break;
 196                 }
 197
 198                 if (state_idx == CPUIDLE_STATE_MAX) {
 199                         pr_warn("State index reached static CPU idle driver states array size\n");
 200                         break;
 201                 }
 202
 203                 idle_state = &drv->states[state_idx++];
 204                 err = init_state_node(idle_state, match_id, state_node);
 205                 if (err) {
 206                         pr_err("Parsing idle state node %pOF failed with err %d\n",
 207                                state_node, err);
 208                         err = -EINVAL;
 209                         break;
 210                 }
 211                 of_node_put(state_node);
 212         }
 213
 214         of_node_put(state_node);
 215         of_node_put(cpu_node);
 216         if (err)
 217                 return err;
 218         /*
 219          * Update the driver state count only if some valid DT idle states
 220          * were detected
 221          */
 222         if (i)
 223                 drv->state_count = state_idx;
 224
 225         /*
 226          * Return the number of present and valid DT idle states, which can
 227          * also be 0 on platforms with missing DT idle states or legacy DT
 228          * configuration predating the DT idle states bindings.
 229          */
 230         return i;
 231 }
 232 EXPORT_SYMBOL_GPL(dt_init_idle_driver);