1 /* 2 * drivers/clocksource/arm_global_timer.c 3 * 4 * Copyright (C) 2013 STMicroelectronics (R&D) Limited. 5 * Author: Stuart Menefy <stuart.menefy@st.com> 6 * Author: Srinivas Kandagatla <srinivas.kandagatla@st.com> 7 * 8 * This program is free software; you can redistribute it and/or modify 9 * it under the terms of the GNU General Public License version 2 as 10 * published by the Free Software Foundation. 11 */ 12 13 #include <linux/init.h> 14 #include <linux/interrupt.h> 15 #include <linux/clocksource.h> 16 #include <linux/clockchips.h> 17 #include <linux/cpu.h> 18 #include <linux/clk.h> 19 #include <linux/delay.h> 20 #include <linux/err.h> 21 #include <linux/io.h> 22 #include <linux/of.h> 23 #include <linux/of_irq.h> 24 #include <linux/of_address.h> 25 #include <linux/sched_clock.h> 26 27 #include <asm/cputype.h> 28 29 #define GT_COUNTER0 0x00 30 #define GT_COUNTER1 0x04 31 32 #define GT_CONTROL 0x08 33 #define GT_CONTROL_TIMER_ENABLE BIT(0) /* this bit is NOT banked */ 34 #define GT_CONTROL_COMP_ENABLE BIT(1) /* banked */ 35 #define GT_CONTROL_IRQ_ENABLE BIT(2) /* banked */ 36 #define GT_CONTROL_AUTO_INC BIT(3) /* banked */ 37 38 #define GT_INT_STATUS 0x0c 39 #define GT_INT_STATUS_EVENT_FLAG BIT(0) 40 41 #define GT_COMP0 0x10 42 #define GT_COMP1 0x14 43 #define GT_AUTO_INC 0x18 44 45 /* 46 * We are expecting to be clocked by the ARM peripheral clock. 47 * 48 * Note: it is assumed we are using a prescaler value of zero, so this is 49 * the units for all operations. 50 */ 51 static void __iomem *gt_base; 52 static unsigned long gt_clk_rate; 53 static int gt_ppi; 54 static struct clock_event_device __percpu *gt_evt; 55 56 /* 57 * To get the value from the Global Timer Counter register proceed as follows: 58 * 1. Read the upper 32-bit timer counter register 59 * 2. Read the lower 32-bit timer counter register 60 * 3. Read the upper 32-bit timer counter register again. If the value is 61 * different to the 32-bit upper value read previously, go back to step 2. 62 * Otherwise the 64-bit timer counter value is correct. 63 */ 64 static u64 notrace _gt_counter_read(void) 65 { 66 u64 counter; 67 u32 lower; 68 u32 upper, old_upper; 69 70 upper = readl_relaxed(gt_base + GT_COUNTER1); 71 do { 72 old_upper = upper; 73 lower = readl_relaxed(gt_base + GT_COUNTER0); 74 upper = readl_relaxed(gt_base + GT_COUNTER1); 75 } while (upper != old_upper); 76 77 counter = upper; 78 counter <<= 32; 79 counter |= lower; 80 return counter; 81 } 82 83 static u64 gt_counter_read(void) 84 { 85 return _gt_counter_read(); 86 } 87 88 /** 89 * To ensure that updates to comparator value register do not set the 90 * Interrupt Status Register proceed as follows: 91 * 1. Clear the Comp Enable bit in the Timer Control Register. 92 * 2. Write the lower 32-bit Comparator Value Register. 93 * 3. Write the upper 32-bit Comparator Value Register. 94 * 4. Set the Comp Enable bit and, if necessary, the IRQ enable bit. 95 */ 96 static void gt_compare_set(unsigned long delta, int periodic) 97 { 98 u64 counter = gt_counter_read(); 99 unsigned long ctrl; 100 101 counter += delta; 102 ctrl = GT_CONTROL_TIMER_ENABLE; 103 writel_relaxed(ctrl, gt_base + GT_CONTROL); 104 writel_relaxed(lower_32_bits(counter), gt_base + GT_COMP0); 105 writel_relaxed(upper_32_bits(counter), gt_base + GT_COMP1); 106 107 if (periodic) { 108 writel_relaxed(delta, gt_base + GT_AUTO_INC); 109 ctrl |= GT_CONTROL_AUTO_INC; 110 } 111 112 ctrl |= GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE; 113 writel_relaxed(ctrl, gt_base + GT_CONTROL); 114 } 115 116 static int gt_clockevent_shutdown(struct clock_event_device *evt) 117 { 118 unsigned long ctrl; 119 120 ctrl = readl(gt_base + GT_CONTROL); 121 ctrl &= ~(GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE | 122 GT_CONTROL_AUTO_INC); 123 writel(ctrl, gt_base + GT_CONTROL); 124 return 0; 125 } 126 127 static int gt_clockevent_set_periodic(struct clock_event_device *evt) 128 { 129 gt_compare_set(DIV_ROUND_CLOSEST(gt_clk_rate, HZ), 1); 130 return 0; 131 } 132 133 static int gt_clockevent_set_next_event(unsigned long evt, 134 struct clock_event_device *unused) 135 { 136 gt_compare_set(evt, 0); 137 return 0; 138 } 139 140 static irqreturn_t gt_clockevent_interrupt(int irq, void *dev_id) 141 { 142 struct clock_event_device *evt = dev_id; 143 144 if (!(readl_relaxed(gt_base + GT_INT_STATUS) & 145 GT_INT_STATUS_EVENT_FLAG)) 146 return IRQ_NONE; 147 148 /** 149 * ERRATA 740657( Global Timer can send 2 interrupts for 150 * the same event in single-shot mode) 151 * Workaround: 152 * Either disable single-shot mode. 153 * Or 154 * Modify the Interrupt Handler to avoid the 155 * offending sequence. This is achieved by clearing 156 * the Global Timer flag _after_ having incremented 157 * the Comparator register value to a higher value. 158 */ 159 if (clockevent_state_oneshot(evt)) 160 gt_compare_set(ULONG_MAX, 0); 161 162 writel_relaxed(GT_INT_STATUS_EVENT_FLAG, gt_base + GT_INT_STATUS); 163 evt->event_handler(evt); 164 165 return IRQ_HANDLED; 166 } 167 168 static int gt_starting_cpu(unsigned int cpu) 169 { 170 struct clock_event_device *clk = this_cpu_ptr(gt_evt); 171 172 clk->name = "arm_global_timer"; 173 clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT | 174 CLOCK_EVT_FEAT_PERCPU; 175 clk->set_state_shutdown = gt_clockevent_shutdown; 176 clk->set_state_periodic = gt_clockevent_set_periodic; 177 clk->set_state_oneshot = gt_clockevent_shutdown; 178 clk->set_state_oneshot_stopped = gt_clockevent_shutdown; 179 clk->set_next_event = gt_clockevent_set_next_event; 180 clk->cpumask = cpumask_of(cpu); 181 clk->rating = 300; 182 clk->irq = gt_ppi; 183 clockevents_config_and_register(clk, gt_clk_rate, 184 1, 0xffffffff); 185 enable_percpu_irq(clk->irq, IRQ_TYPE_NONE); 186 return 0; 187 } 188 189 static int gt_dying_cpu(unsigned int cpu) 190 { 191 struct clock_event_device *clk = this_cpu_ptr(gt_evt); 192 193 gt_clockevent_shutdown(clk); 194 disable_percpu_irq(clk->irq); 195 return 0; 196 } 197 198 static u64 gt_clocksource_read(struct clocksource *cs) 199 { 200 return gt_counter_read(); 201 } 202 203 static void gt_resume(struct clocksource *cs) 204 { 205 unsigned long ctrl; 206 207 ctrl = readl(gt_base + GT_CONTROL); 208 if (!(ctrl & GT_CONTROL_TIMER_ENABLE)) 209 /* re-enable timer on resume */ 210 writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL); 211 } 212 213 static struct clocksource gt_clocksource = { 214 .name = "arm_global_timer", 215 .rating = 300, 216 .read = gt_clocksource_read, 217 .mask = CLOCKSOURCE_MASK(64), 218 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 219 .resume = gt_resume, 220 }; 221 222 #ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK 223 static u64 notrace gt_sched_clock_read(void) 224 { 225 return _gt_counter_read(); 226 } 227 #endif 228 229 static unsigned long gt_read_long(void) 230 { 231 return readl_relaxed(gt_base + GT_COUNTER0); 232 } 233 234 static struct delay_timer gt_delay_timer = { 235 .read_current_timer = gt_read_long, 236 }; 237 238 static void __init gt_delay_timer_init(void) 239 { 240 gt_delay_timer.freq = gt_clk_rate; 241 register_current_timer_delay(>_delay_timer); 242 } 243 244 static int __init gt_clocksource_init(void) 245 { 246 writel(0, gt_base + GT_CONTROL); 247 writel(0, gt_base + GT_COUNTER0); 248 writel(0, gt_base + GT_COUNTER1); 249 /* enables timer on all the cores */ 250 writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL); 251 252 #ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK 253 sched_clock_register(gt_sched_clock_read, 64, gt_clk_rate); 254 #endif 255 return clocksource_register_hz(>_clocksource, gt_clk_rate); 256 } 257 258 static int __init global_timer_of_register(struct device_node *np) 259 { 260 struct clk *gt_clk; 261 int err = 0; 262 263 /* 264 * In A9 r2p0 the comparators for each processor with the global timer 265 * fire when the timer value is greater than or equal to. In previous 266 * revisions the comparators fired when the timer value was equal to. 267 */ 268 if (read_cpuid_part() == ARM_CPU_PART_CORTEX_A9 269 && (read_cpuid_id() & 0xf0000f) < 0x200000) { 270 pr_warn("global-timer: non support for this cpu version.\n"); 271 return -ENOSYS; 272 } 273 274 gt_ppi = irq_of_parse_and_map(np, 0); 275 if (!gt_ppi) { 276 pr_warn("global-timer: unable to parse irq\n"); 277 return -EINVAL; 278 } 279 280 gt_base = of_iomap(np, 0); 281 if (!gt_base) { 282 pr_warn("global-timer: invalid base address\n"); 283 return -ENXIO; 284 } 285 286 gt_clk = of_clk_get(np, 0); 287 if (!IS_ERR(gt_clk)) { 288 err = clk_prepare_enable(gt_clk); 289 if (err) 290 goto out_unmap; 291 } else { 292 pr_warn("global-timer: clk not found\n"); 293 err = -EINVAL; 294 goto out_unmap; 295 } 296 297 gt_clk_rate = clk_get_rate(gt_clk); 298 gt_evt = alloc_percpu(struct clock_event_device); 299 if (!gt_evt) { 300 pr_warn("global-timer: can't allocate memory\n"); 301 err = -ENOMEM; 302 goto out_clk; 303 } 304 305 err = request_percpu_irq(gt_ppi, gt_clockevent_interrupt, 306 "gt", gt_evt); 307 if (err) { 308 pr_warn("global-timer: can't register interrupt %d (%d)\n", 309 gt_ppi, err); 310 goto out_free; 311 } 312 313 /* Register and immediately configure the timer on the boot CPU */ 314 err = gt_clocksource_init(); 315 if (err) 316 goto out_irq; 317 318 err = cpuhp_setup_state(CPUHP_AP_ARM_GLOBAL_TIMER_STARTING, 319 "clockevents/arm/global_timer:starting", 320 gt_starting_cpu, gt_dying_cpu); 321 if (err) 322 goto out_irq; 323 324 gt_delay_timer_init(); 325 326 return 0; 327 328 out_irq: 329 free_percpu_irq(gt_ppi, gt_evt); 330 out_free: 331 free_percpu(gt_evt); 332 out_clk: 333 clk_disable_unprepare(gt_clk); 334 out_unmap: 335 iounmap(gt_base); 336 WARN(err, "ARM Global timer register failed (%d)\n", err); 337 338 return err; 339 } 340 341 /* Only tested on r2p2 and r3p0 */ 342 TIMER_OF_DECLARE(arm_gt, "arm,cortex-a9-global-timer", 343 global_timer_of_register); 344