dt_idle_states.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * DT idle states parsing code.
  4 *
  5 * Copyright (C) 2014 ARM Ltd.
  6 * Author: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
  7 */
  8
  9#define pr_fmt(fmt) "DT idle-states: " fmt
 10
 11#include <linux/cpuidle.h>
 12#include <linux/cpumask.h>
 13#include <linux/errno.h>
 14#include <linux/kernel.h>
 15#include <linux/module.h>
 16#include <linux/of.h>
 17
 18#include "dt_idle_states.h"
 19
 20static int init_state_node(struct cpuidle_state *idle_state,
 21			   const struct of_device_id *match_id,
 22			   struct device_node *state_node)
 23{
 24	int err;
 25	const char *desc;
 26
 27	/*
 28	 * CPUidle drivers are expected to initialize the const void *data
 29	 * pointer of the passed in struct of_device_id array to the idle
 30	 * state enter function.
 31	 */
 32	idle_state->enter = match_id->data;
 33	/*
 34	 * Since this is not a "coupled" state, it's safe to assume interrupts
 35	 * won't be enabled when it exits allowing the tick to be frozen
 36	 * safely. So enter() can be also enter_s2idle() callback.
 37	 */
 38	idle_state->enter_s2idle = match_id->data;
 39
 40	err = of_property_read_u32(state_node, "wakeup-latency-us",
 41				   &idle_state->exit_latency);
 42	if (err) {
 43		u32 entry_latency, exit_latency;
 44
 45		err = of_property_read_u32(state_node, "entry-latency-us",
 46					   &entry_latency);
 47		if (err) {
 48			pr_debug(" * %pOF missing entry-latency-us property\n",
 49				 state_node);
 50			return -EINVAL;
 51		}
 52
 53		err = of_property_read_u32(state_node, "exit-latency-us",
 54					   &exit_latency);
 55		if (err) {
 56			pr_debug(" * %pOF missing exit-latency-us property\n",
 57				 state_node);
 58			return -EINVAL;
 59		}
 60		/*
 61		 * If wakeup-latency-us is missing, default to entry+exit
 62		 * latencies as defined in idle states bindings
 63		 */
 64		idle_state->exit_latency = entry_latency + exit_latency;
 65	}
 66
 67	err = of_property_read_u32(state_node, "min-residency-us",
 68				   &idle_state->target_residency);
 69	if (err) {
 70		pr_debug(" * %pOF missing min-residency-us property\n",
 71			     state_node);
 72		return -EINVAL;
 73	}
 74
 75	err = of_property_read_string(state_node, "idle-state-name", &desc);
 76	if (err)
 77		desc = state_node->name;
 78
 79	idle_state->flags = CPUIDLE_FLAG_RCU_IDLE;
 80	if (of_property_read_bool(state_node, "local-timer-stop"))
 81		idle_state->flags |= CPUIDLE_FLAG_TIMER_STOP;
 82	/*
 83	 * TODO:
 84	 *	replace with kstrdup and pointer assignment when name
 85	 *	and desc become string pointers
 86	 */
 87	strscpy(idle_state->name, state_node->name, CPUIDLE_NAME_LEN);
 88	strscpy(idle_state->desc, desc, CPUIDLE_DESC_LEN);
 89	return 0;
 90}
 91
 92/*
 93 * Check that the idle state is uniform across all CPUs in the CPUidle driver
 94 * cpumask
 95 */
 96static bool idle_state_valid(struct device_node *state_node, unsigned int idx,
 97			     const cpumask_t *cpumask)
 98{
 99	int cpu;
100	struct device_node *cpu_node, *curr_state_node;
101
102	/*
103	 * Compare idle state phandles for index idx on all CPUs in the
104	 * CPUidle driver cpumask. Start from next logical cpu following
105	 * cpumask_first(cpumask) since that's the CPU state_node was
106	 * retrieved from. If a mismatch is found bail out straight
107	 * away since we certainly hit a firmware misconfiguration.
108	 */
109	cpu = cpumask_first(cpumask) + 1;
110	for_each_cpu_from(cpu, cpumask) {
111		cpu_node = of_cpu_device_node_get(cpu);
112		curr_state_node = of_get_cpu_state_node(cpu_node, idx);
113		of_node_put(curr_state_node);
114		of_node_put(cpu_node);
115		if (state_node != curr_state_node)
116			return false;
117	}
118
119	return true;
120}
121
122/**
123 * dt_init_idle_driver() - Parse the DT idle states and initialize the
124 *			   idle driver states array
125 * @drv:	  Pointer to CPU idle driver to be initialized
126 * @matches:	  Array of of_device_id match structures to search in for
127 *		  compatible idle state nodes. The data pointer for each valid
128 *		  struct of_device_id entry in the matches array must point to
129 *		  a function with the following signature, that corresponds to
130 *		  the CPUidle state enter function signature:
131 *
132 *		  int (*)(struct cpuidle_device *dev,
133 *			  struct cpuidle_driver *drv,
134 *			  int index);
135 *
136 * @start_idx:    First idle state index to be initialized
137 *
138 * If DT idle states are detected and are valid the state count and states
139 * array entries in the cpuidle driver are initialized accordingly starting
140 * from index start_idx.
141 *
142 * Return: number of valid DT idle states parsed, <0 on failure
143 */
144int dt_init_idle_driver(struct cpuidle_driver *drv,
145			const struct of_device_id *matches,
146			unsigned int start_idx)
147{
148	struct cpuidle_state *idle_state;
149	struct device_node *state_node, *cpu_node;
150	const struct of_device_id *match_id;
151	int i, err = 0;
152	const cpumask_t *cpumask;
153	unsigned int state_idx = start_idx;
154
155	if (state_idx >= CPUIDLE_STATE_MAX)
156		return -EINVAL;
157	/*
158	 * We get the idle states for the first logical cpu in the
159	 * driver mask (or cpu_possible_mask if the driver cpumask is not set)
160	 * and we check through idle_state_valid() if they are uniform
161	 * across CPUs, otherwise we hit a firmware misconfiguration.
162	 */
163	cpumask = drv->cpumask ? : cpu_possible_mask;
164	cpu_node = of_cpu_device_node_get(cpumask_first(cpumask));
165
166	for (i = 0; ; i++) {
167		state_node = of_get_cpu_state_node(cpu_node, i);
168		if (!state_node)
169			break;
170
171		match_id = of_match_node(matches, state_node);
172		if (!match_id) {
173			err = -ENODEV;
174			break;
175		}
176
177		if (!of_device_is_available(state_node)) {
178			of_node_put(state_node);
179			continue;
180		}
181
182		if (!idle_state_valid(state_node, i, cpumask)) {
183			pr_warn("%pOF idle state not valid, bailing out\n",
184				state_node);
185			err = -EINVAL;
186			break;
187		}
188
189		if (state_idx == CPUIDLE_STATE_MAX) {
190			pr_warn("State index reached static CPU idle driver states array size\n");
191			break;
192		}
193
194		idle_state = &drv->states[state_idx++];
195		err = init_state_node(idle_state, match_id, state_node);
196		if (err) {
197			pr_err("Parsing idle state node %pOF failed with err %d\n",
198			       state_node, err);
199			err = -EINVAL;
200			break;
201		}
202		of_node_put(state_node);
203	}
204
205	of_node_put(state_node);
206	of_node_put(cpu_node);
207	if (err)
208		return err;
209
210	/* Set the number of total supported idle states. */
211	drv->state_count = state_idx;
212
213	/*
214	 * Return the number of present and valid DT idle states, which can
215	 * also be 0 on platforms with missing DT idle states or legacy DT
216	 * configuration predating the DT idle states bindings.
217	 */
218	return state_idx - start_idx;
219}
220EXPORT_SYMBOL_GPL(dt_init_idle_driver);