1 /* 2 * linux/arch/arm/kernel/smp_twd.c 3 * 4 * Copyright (C) 2002 ARM Ltd. 5 * All Rights Reserved 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 #include <linux/init.h> 12 #include <linux/kernel.h> 13 #include <linux/clk.h> 14 #include <linux/cpu.h> 15 #include <linux/delay.h> 16 #include <linux/device.h> 17 #include <linux/err.h> 18 #include <linux/smp.h> 19 #include <linux/jiffies.h> 20 #include <linux/clockchips.h> 21 #include <linux/interrupt.h> 22 #include <linux/io.h> 23 #include <linux/of_irq.h> 24 #include <linux/of_address.h> 25 26 #include <asm/smp_twd.h> 27 28 /* set up by the platform code */ 29 static void __iomem *twd_base; 30 31 static struct clk *twd_clk; 32 static unsigned long twd_timer_rate; 33 static DEFINE_PER_CPU(bool, percpu_setup_called); 34 35 static struct clock_event_device __percpu *twd_evt; 36 static unsigned int twd_features = 37 CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT; 38 static int twd_ppi; 39 40 static int twd_shutdown(struct clock_event_device *clk) 41 { 42 writel_relaxed(0, twd_base + TWD_TIMER_CONTROL); 43 return 0; 44 } 45 46 static int twd_set_oneshot(struct clock_event_device *clk) 47 { 48 /* period set, and timer enabled in 'next_event' hook */ 49 writel_relaxed(TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT, 50 twd_base + TWD_TIMER_CONTROL); 51 return 0; 52 } 53 54 static int twd_set_periodic(struct clock_event_device *clk) 55 { 56 unsigned long ctrl = TWD_TIMER_CONTROL_ENABLE | 57 TWD_TIMER_CONTROL_IT_ENABLE | 58 TWD_TIMER_CONTROL_PERIODIC; 59 60 writel_relaxed(DIV_ROUND_CLOSEST(twd_timer_rate, HZ), 61 twd_base + TWD_TIMER_LOAD); 62 writel_relaxed(ctrl, twd_base + TWD_TIMER_CONTROL); 63 return 0; 64 } 65 66 static int twd_set_next_event(unsigned long evt, 67 struct clock_event_device *unused) 68 { 69 unsigned long ctrl = readl_relaxed(twd_base + TWD_TIMER_CONTROL); 70 71 ctrl |= TWD_TIMER_CONTROL_ENABLE; 72 73 writel_relaxed(evt, twd_base + TWD_TIMER_COUNTER); 74 writel_relaxed(ctrl, twd_base + TWD_TIMER_CONTROL); 75 76 return 0; 77 } 78 79 /* 80 * local_timer_ack: checks for a local timer interrupt. 81 * 82 * If a local timer interrupt has occurred, acknowledge and return 1. 83 * Otherwise, return 0. 84 */ 85 static int twd_timer_ack(void) 86 { 87 if (readl_relaxed(twd_base + TWD_TIMER_INTSTAT)) { 88 writel_relaxed(1, twd_base + TWD_TIMER_INTSTAT); 89 return 1; 90 } 91 92 return 0; 93 } 94 95 static void twd_timer_stop(void) 96 { 97 struct clock_event_device *clk = raw_cpu_ptr(twd_evt); 98 99 twd_shutdown(clk); 100 disable_percpu_irq(clk->irq); 101 } 102 103 /* 104 * Updates clockevent frequency when the cpu frequency changes. 105 * Called on the cpu that is changing frequency with interrupts disabled. 106 */ 107 static void twd_update_frequency(void *new_rate) 108 { 109 twd_timer_rate = *((unsigned long *) new_rate); 110 111 clockevents_update_freq(raw_cpu_ptr(twd_evt), twd_timer_rate); 112 } 113 114 static int twd_rate_change(struct notifier_block *nb, 115 unsigned long flags, void *data) 116 { 117 struct clk_notifier_data *cnd = data; 118 119 /* 120 * The twd clock events must be reprogrammed to account for the new 121 * frequency. The timer is local to a cpu, so cross-call to the 122 * changing cpu. 123 */ 124 if (flags == POST_RATE_CHANGE) 125 on_each_cpu(twd_update_frequency, 126 (void *)&cnd->new_rate, 1); 127 128 return NOTIFY_OK; 129 } 130 131 static struct notifier_block twd_clk_nb = { 132 .notifier_call = twd_rate_change, 133 }; 134 135 static int twd_clk_init(void) 136 { 137 if (twd_evt && raw_cpu_ptr(twd_evt) && !IS_ERR(twd_clk)) 138 return clk_notifier_register(twd_clk, &twd_clk_nb); 139 140 return 0; 141 } 142 core_initcall(twd_clk_init); 143 144 static void twd_calibrate_rate(void) 145 { 146 unsigned long count; 147 u64 waitjiffies; 148 149 /* 150 * If this is the first time round, we need to work out how fast 151 * the timer ticks 152 */ 153 if (twd_timer_rate == 0) { 154 pr_info("Calibrating local timer... "); 155 156 /* Wait for a tick to start */ 157 waitjiffies = get_jiffies_64() + 1; 158 159 while (get_jiffies_64() < waitjiffies) 160 udelay(10); 161 162 /* OK, now the tick has started, let's get the timer going */ 163 waitjiffies += 5; 164 165 /* enable, no interrupt or reload */ 166 writel_relaxed(0x1, twd_base + TWD_TIMER_CONTROL); 167 168 /* maximum value */ 169 writel_relaxed(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER); 170 171 while (get_jiffies_64() < waitjiffies) 172 udelay(10); 173 174 count = readl_relaxed(twd_base + TWD_TIMER_COUNTER); 175 176 twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5); 177 178 pr_cont("%lu.%02luMHz.\n", twd_timer_rate / 1000000, 179 (twd_timer_rate / 10000) % 100); 180 } 181 } 182 183 static irqreturn_t twd_handler(int irq, void *dev_id) 184 { 185 struct clock_event_device *evt = dev_id; 186 187 if (twd_timer_ack()) { 188 evt->event_handler(evt); 189 return IRQ_HANDLED; 190 } 191 192 return IRQ_NONE; 193 } 194 195 static void twd_get_clock(struct device_node *np) 196 { 197 int err; 198 199 if (np) 200 twd_clk = of_clk_get(np, 0); 201 else 202 twd_clk = clk_get_sys("smp_twd", NULL); 203 204 if (IS_ERR(twd_clk)) { 205 pr_err("smp_twd: clock not found %d\n", (int) PTR_ERR(twd_clk)); 206 return; 207 } 208 209 err = clk_prepare_enable(twd_clk); 210 if (err) { 211 pr_err("smp_twd: clock failed to prepare+enable: %d\n", err); 212 clk_put(twd_clk); 213 return; 214 } 215 216 twd_timer_rate = clk_get_rate(twd_clk); 217 } 218 219 /* 220 * Setup the local clock events for a CPU. 221 */ 222 static void twd_timer_setup(void) 223 { 224 struct clock_event_device *clk = raw_cpu_ptr(twd_evt); 225 int cpu = smp_processor_id(); 226 227 /* 228 * If the basic setup for this CPU has been done before don't 229 * bother with the below. 230 */ 231 if (per_cpu(percpu_setup_called, cpu)) { 232 writel_relaxed(0, twd_base + TWD_TIMER_CONTROL); 233 clockevents_register_device(clk); 234 enable_percpu_irq(clk->irq, 0); 235 return; 236 } 237 per_cpu(percpu_setup_called, cpu) = true; 238 239 twd_calibrate_rate(); 240 241 /* 242 * The following is done once per CPU the first time .setup() is 243 * called. 244 */ 245 writel_relaxed(0, twd_base + TWD_TIMER_CONTROL); 246 247 clk->name = "local_timer"; 248 clk->features = twd_features; 249 clk->rating = 350; 250 clk->set_state_shutdown = twd_shutdown; 251 clk->set_state_periodic = twd_set_periodic; 252 clk->set_state_oneshot = twd_set_oneshot; 253 clk->tick_resume = twd_shutdown; 254 clk->set_next_event = twd_set_next_event; 255 clk->irq = twd_ppi; 256 clk->cpumask = cpumask_of(cpu); 257 258 clockevents_config_and_register(clk, twd_timer_rate, 259 0xf, 0xffffffff); 260 enable_percpu_irq(clk->irq, 0); 261 } 262 263 static int twd_timer_starting_cpu(unsigned int cpu) 264 { 265 twd_timer_setup(); 266 return 0; 267 } 268 269 static int twd_timer_dying_cpu(unsigned int cpu) 270 { 271 twd_timer_stop(); 272 return 0; 273 } 274 275 static int __init twd_local_timer_common_register(struct device_node *np) 276 { 277 int err; 278 279 twd_evt = alloc_percpu(struct clock_event_device); 280 if (!twd_evt) { 281 err = -ENOMEM; 282 goto out_free; 283 } 284 285 err = request_percpu_irq(twd_ppi, twd_handler, "twd", twd_evt); 286 if (err) { 287 pr_err("twd: can't register interrupt %d (%d)\n", twd_ppi, err); 288 goto out_free; 289 } 290 291 cpuhp_setup_state_nocalls(CPUHP_AP_ARM_TWD_STARTING, 292 "arm/timer/twd:starting", 293 twd_timer_starting_cpu, twd_timer_dying_cpu); 294 295 twd_get_clock(np); 296 if (!of_property_read_bool(np, "always-on")) 297 twd_features |= CLOCK_EVT_FEAT_C3STOP; 298 299 /* 300 * Immediately configure the timer on the boot CPU, unless we need 301 * jiffies to be incrementing to calibrate the rate in which case 302 * setup the timer in late_time_init. 303 */ 304 if (twd_timer_rate) 305 twd_timer_setup(); 306 else 307 late_time_init = twd_timer_setup; 308 309 return 0; 310 311 out_free: 312 iounmap(twd_base); 313 twd_base = NULL; 314 free_percpu(twd_evt); 315 316 return err; 317 } 318 319 static int __init twd_local_timer_of_register(struct device_node *np) 320 { 321 int err; 322 323 twd_ppi = irq_of_parse_and_map(np, 0); 324 if (!twd_ppi) { 325 err = -EINVAL; 326 goto out; 327 } 328 329 twd_base = of_iomap(np, 0); 330 if (!twd_base) { 331 err = -ENOMEM; 332 goto out; 333 } 334 335 err = twd_local_timer_common_register(np); 336 337 out: 338 WARN(err, "twd_local_timer_of_register failed (%d)\n", err); 339 return err; 340 } 341 TIMER_OF_DECLARE(arm_twd_a9, "arm,cortex-a9-twd-timer", twd_local_timer_of_register); 342 TIMER_OF_DECLARE(arm_twd_a5, "arm,cortex-a5-twd-timer", twd_local_timer_of_register); 343 TIMER_OF_DECLARE(arm_twd_11mp, "arm,arm11mp-twd-timer", twd_local_timer_of_register); 344