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);
214