1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * linux/arch/parisc/kernel/time.c 4 * 5 * Copyright (C) 1991, 1992, 1995 Linus Torvalds 6 * Modifications for ARM (C) 1994, 1995, 1996,1997 Russell King 7 * Copyright (C) 1999 SuSE GmbH, (Philipp Rumpf, prumpf@tux.org) 8 * 9 * 1994-07-02 Alan Modra 10 * fixed set_rtc_mmss, fixed time.year for >= 2000, new mktime 11 * 1998-12-20 Updated NTP code according to technical memorandum Jan '96 12 * "A Kernel Model for Precision Timekeeping" by Dave Mills 13 */ 14 #include <linux/errno.h> 15 #include <linux/module.h> 16 #include <linux/rtc.h> 17 #include <linux/sched.h> 18 #include <linux/sched/clock.h> 19 #include <linux/sched_clock.h> 20 #include <linux/kernel.h> 21 #include <linux/param.h> 22 #include <linux/string.h> 23 #include <linux/mm.h> 24 #include <linux/interrupt.h> 25 #include <linux/time.h> 26 #include <linux/init.h> 27 #include <linux/smp.h> 28 #include <linux/profile.h> 29 #include <linux/clocksource.h> 30 #include <linux/platform_device.h> 31 #include <linux/ftrace.h> 32 33 #include <linux/uaccess.h> 34 #include <asm/io.h> 35 #include <asm/irq.h> 36 #include <asm/page.h> 37 #include <asm/param.h> 38 #include <asm/pdc.h> 39 #include <asm/led.h> 40 41 #include <linux/timex.h> 42 43 static unsigned long clocktick __read_mostly; /* timer cycles per tick */ 44 45 /* 46 * We keep time on PA-RISC Linux by using the Interval Timer which is 47 * a pair of registers; one is read-only and one is write-only; both 48 * accessed through CR16. The read-only register is 32 or 64 bits wide, 49 * and increments by 1 every CPU clock tick. The architecture only 50 * guarantees us a rate between 0.5 and 2, but all implementations use a 51 * rate of 1. The write-only register is 32-bits wide. When the lowest 52 * 32 bits of the read-only register compare equal to the write-only 53 * register, it raises a maskable external interrupt. Each processor has 54 * an Interval Timer of its own and they are not synchronised. 55 * 56 * We want to generate an interrupt every 1/HZ seconds. So we program 57 * CR16 to interrupt every @clocktick cycles. The it_value in cpu_data 58 * is programmed with the intended time of the next tick. We can be 59 * held off for an arbitrarily long period of time by interrupts being 60 * disabled, so we may miss one or more ticks. 61 */ 62 irqreturn_t __irq_entry timer_interrupt(int irq, void *dev_id) 63 { 64 unsigned long now; 65 unsigned long next_tick; 66 unsigned long ticks_elapsed = 0; 67 unsigned int cpu = smp_processor_id(); 68 struct cpuinfo_parisc *cpuinfo = &per_cpu(cpu_data, cpu); 69 70 /* gcc can optimize for "read-only" case with a local clocktick */ 71 unsigned long cpt = clocktick; 72 73 profile_tick(CPU_PROFILING); 74 75 /* Initialize next_tick to the old expected tick time. */ 76 next_tick = cpuinfo->it_value; 77 78 /* Calculate how many ticks have elapsed. */ 79 do { 80 ++ticks_elapsed; 81 next_tick += cpt; 82 now = mfctl(16); 83 } while (next_tick - now > cpt); 84 85 /* Store (in CR16 cycles) up to when we are accounting right now. */ 86 cpuinfo->it_value = next_tick; 87 88 /* Go do system house keeping. */ 89 if (cpu == 0) 90 xtime_update(ticks_elapsed); 91 92 update_process_times(user_mode(get_irq_regs())); 93 94 /* Skip clockticks on purpose if we know we would miss those. 95 * The new CR16 must be "later" than current CR16 otherwise 96 * itimer would not fire until CR16 wrapped - e.g 4 seconds 97 * later on a 1Ghz processor. We'll account for the missed 98 * ticks on the next timer interrupt. 99 * We want IT to fire modulo clocktick even if we miss/skip some. 100 * But those interrupts don't in fact get delivered that regularly. 101 * 102 * "next_tick - now" will always give the difference regardless 103 * if one or the other wrapped. If "now" is "bigger" we'll end up 104 * with a very large unsigned number. 105 */ 106 while (next_tick - mfctl(16) > cpt) 107 next_tick += cpt; 108 109 /* Program the IT when to deliver the next interrupt. 110 * Only bottom 32-bits of next_tick are writable in CR16! 111 * Timer interrupt will be delivered at least a few hundred cycles 112 * after the IT fires, so if we are too close (<= 500 cycles) to the 113 * next cycle, simply skip it. 114 */ 115 if (next_tick - mfctl(16) <= 500) 116 next_tick += cpt; 117 mtctl(next_tick, 16); 118 119 return IRQ_HANDLED; 120 } 121 122 123 unsigned long profile_pc(struct pt_regs *regs) 124 { 125 unsigned long pc = instruction_pointer(regs); 126 127 if (regs->gr[0] & PSW_N) 128 pc -= 4; 129 130 #ifdef CONFIG_SMP 131 if (in_lock_functions(pc)) 132 pc = regs->gr[2]; 133 #endif 134 135 return pc; 136 } 137 EXPORT_SYMBOL(profile_pc); 138 139 140 /* clock source code */ 141 142 static u64 notrace read_cr16(struct clocksource *cs) 143 { 144 return get_cycles(); 145 } 146 147 static struct clocksource clocksource_cr16 = { 148 .name = "cr16", 149 .rating = 300, 150 .read = read_cr16, 151 .mask = CLOCKSOURCE_MASK(BITS_PER_LONG), 152 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 153 }; 154 155 void __init start_cpu_itimer(void) 156 { 157 unsigned int cpu = smp_processor_id(); 158 unsigned long next_tick = mfctl(16) + clocktick; 159 160 mtctl(next_tick, 16); /* kick off Interval Timer (CR16) */ 161 162 per_cpu(cpu_data, cpu).it_value = next_tick; 163 } 164 165 #if IS_ENABLED(CONFIG_RTC_DRV_GENERIC) 166 static int rtc_generic_get_time(struct device *dev, struct rtc_time *tm) 167 { 168 struct pdc_tod tod_data; 169 170 memset(tm, 0, sizeof(*tm)); 171 if (pdc_tod_read(&tod_data) < 0) 172 return -EOPNOTSUPP; 173 174 /* we treat tod_sec as unsigned, so this can work until year 2106 */ 175 rtc_time64_to_tm(tod_data.tod_sec, tm); 176 return rtc_valid_tm(tm); 177 } 178 179 static int rtc_generic_set_time(struct device *dev, struct rtc_time *tm) 180 { 181 time64_t secs = rtc_tm_to_time64(tm); 182 183 if (pdc_tod_set(secs, 0) < 0) 184 return -EOPNOTSUPP; 185 186 return 0; 187 } 188 189 static const struct rtc_class_ops rtc_generic_ops = { 190 .read_time = rtc_generic_get_time, 191 .set_time = rtc_generic_set_time, 192 }; 193 194 static int __init rtc_init(void) 195 { 196 struct platform_device *pdev; 197 198 pdev = platform_device_register_data(NULL, "rtc-generic", -1, 199 &rtc_generic_ops, 200 sizeof(rtc_generic_ops)); 201 202 return PTR_ERR_OR_ZERO(pdev); 203 } 204 device_initcall(rtc_init); 205 #endif 206 207 void read_persistent_clock(struct timespec *ts) 208 { 209 static struct pdc_tod tod_data; 210 if (pdc_tod_read(&tod_data) == 0) { 211 ts->tv_sec = tod_data.tod_sec; 212 ts->tv_nsec = tod_data.tod_usec * 1000; 213 } else { 214 printk(KERN_ERR "Error reading tod clock\n"); 215 ts->tv_sec = 0; 216 ts->tv_nsec = 0; 217 } 218 } 219 220 221 static u64 notrace read_cr16_sched_clock(void) 222 { 223 return get_cycles(); 224 } 225 226 227 /* 228 * timer interrupt and sched_clock() initialization 229 */ 230 231 void __init time_init(void) 232 { 233 unsigned long cr16_hz; 234 235 clocktick = (100 * PAGE0->mem_10msec) / HZ; 236 start_cpu_itimer(); /* get CPU 0 started */ 237 238 cr16_hz = 100 * PAGE0->mem_10msec; /* Hz */ 239 240 /* register as sched_clock source */ 241 sched_clock_register(read_cr16_sched_clock, BITS_PER_LONG, cr16_hz); 242 } 243 244 static int __init init_cr16_clocksource(void) 245 { 246 /* 247 * The cr16 interval timers are not syncronized across CPUs on 248 * different sockets, so mark them unstable and lower rating on 249 * multi-socket SMP systems. 250 */ 251 if (num_online_cpus() > 1) { 252 int cpu; 253 unsigned long cpu0_loc; 254 cpu0_loc = per_cpu(cpu_data, 0).cpu_loc; 255 256 for_each_online_cpu(cpu) { 257 if (cpu == 0) 258 continue; 259 if ((cpu0_loc != 0) && 260 (cpu0_loc == per_cpu(cpu_data, cpu).cpu_loc)) 261 continue; 262 263 clocksource_cr16.name = "cr16_unstable"; 264 clocksource_cr16.flags = CLOCK_SOURCE_UNSTABLE; 265 clocksource_cr16.rating = 0; 266 break; 267 } 268 } 269 270 /* XXX: We may want to mark sched_clock stable here if cr16 clocks are 271 * in sync: 272 * (clocksource_cr16.flags == CLOCK_SOURCE_IS_CONTINUOUS) */ 273 274 /* register at clocksource framework */ 275 clocksource_register_hz(&clocksource_cr16, 276 100 * PAGE0->mem_10msec); 277 278 return 0; 279 } 280 281 device_initcall(init_cr16_clocksource); 282