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 now = mfctl(16); 80 do { 81 ++ticks_elapsed; 82 next_tick += cpt; 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 now = mfctl(16); 107 while (next_tick - now > cpt) 108 next_tick += cpt; 109 110 /* Program the IT when to deliver the next interrupt. 111 * Only bottom 32-bits of next_tick are writable in CR16! 112 * Timer interrupt will be delivered at least a few hundred cycles 113 * after the IT fires, so if we are too close (<= 8000 cycles) to the 114 * next cycle, simply skip it. 115 */ 116 if (next_tick - now <= 8000) 117 next_tick += cpt; 118 mtctl(next_tick, 16); 119 120 return IRQ_HANDLED; 121 } 122 123 124 unsigned long profile_pc(struct pt_regs *regs) 125 { 126 unsigned long pc = instruction_pointer(regs); 127 128 if (regs->gr[0] & PSW_N) 129 pc -= 4; 130 131 #ifdef CONFIG_SMP 132 if (in_lock_functions(pc)) 133 pc = regs->gr[2]; 134 #endif 135 136 return pc; 137 } 138 EXPORT_SYMBOL(profile_pc); 139 140 141 /* clock source code */ 142 143 static u64 notrace read_cr16(struct clocksource *cs) 144 { 145 return get_cycles(); 146 } 147 148 static struct clocksource clocksource_cr16 = { 149 .name = "cr16", 150 .rating = 300, 151 .read = read_cr16, 152 .mask = CLOCKSOURCE_MASK(BITS_PER_LONG), 153 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 154 }; 155 156 void __init start_cpu_itimer(void) 157 { 158 unsigned int cpu = smp_processor_id(); 159 unsigned long next_tick = mfctl(16) + clocktick; 160 161 mtctl(next_tick, 16); /* kick off Interval Timer (CR16) */ 162 163 per_cpu(cpu_data, cpu).it_value = next_tick; 164 } 165 166 #if IS_ENABLED(CONFIG_RTC_DRV_GENERIC) 167 static int rtc_generic_get_time(struct device *dev, struct rtc_time *tm) 168 { 169 struct pdc_tod tod_data; 170 171 memset(tm, 0, sizeof(*tm)); 172 if (pdc_tod_read(&tod_data) < 0) 173 return -EOPNOTSUPP; 174 175 /* we treat tod_sec as unsigned, so this can work until year 2106 */ 176 rtc_time64_to_tm(tod_data.tod_sec, tm); 177 return 0; 178 } 179 180 static int rtc_generic_set_time(struct device *dev, struct rtc_time *tm) 181 { 182 time64_t secs = rtc_tm_to_time64(tm); 183 184 if (pdc_tod_set(secs, 0) < 0) 185 return -EOPNOTSUPP; 186 187 return 0; 188 } 189 190 static const struct rtc_class_ops rtc_generic_ops = { 191 .read_time = rtc_generic_get_time, 192 .set_time = rtc_generic_set_time, 193 }; 194 195 static int __init rtc_init(void) 196 { 197 struct platform_device *pdev; 198 199 pdev = platform_device_register_data(NULL, "rtc-generic", -1, 200 &rtc_generic_ops, 201 sizeof(rtc_generic_ops)); 202 203 return PTR_ERR_OR_ZERO(pdev); 204 } 205 device_initcall(rtc_init); 206 #endif 207 208 void read_persistent_clock64(struct timespec64 *ts) 209 { 210 static struct pdc_tod tod_data; 211 if (pdc_tod_read(&tod_data) == 0) { 212 ts->tv_sec = tod_data.tod_sec; 213 ts->tv_nsec = tod_data.tod_usec * 1000; 214 } else { 215 printk(KERN_ERR "Error reading tod clock\n"); 216 ts->tv_sec = 0; 217 ts->tv_nsec = 0; 218 } 219 } 220 221 222 static u64 notrace read_cr16_sched_clock(void) 223 { 224 return get_cycles(); 225 } 226 227 228 /* 229 * timer interrupt and sched_clock() initialization 230 */ 231 232 void __init time_init(void) 233 { 234 unsigned long cr16_hz; 235 236 clocktick = (100 * PAGE0->mem_10msec) / HZ; 237 start_cpu_itimer(); /* get CPU 0 started */ 238 239 cr16_hz = 100 * PAGE0->mem_10msec; /* Hz */ 240 241 /* register as sched_clock source */ 242 sched_clock_register(read_cr16_sched_clock, BITS_PER_LONG, cr16_hz); 243 } 244 245 static int __init init_cr16_clocksource(void) 246 { 247 /* 248 * The cr16 interval timers are not syncronized across CPUs on 249 * different sockets, so mark them unstable and lower rating on 250 * multi-socket SMP systems. 251 */ 252 if (num_online_cpus() > 1 && !running_on_qemu) { 253 int cpu; 254 unsigned long cpu0_loc; 255 cpu0_loc = per_cpu(cpu_data, 0).cpu_loc; 256 257 for_each_online_cpu(cpu) { 258 if (cpu == 0) 259 continue; 260 if ((cpu0_loc != 0) && 261 (cpu0_loc == per_cpu(cpu_data, cpu).cpu_loc)) 262 continue; 263 264 clocksource_cr16.name = "cr16_unstable"; 265 clocksource_cr16.flags = CLOCK_SOURCE_UNSTABLE; 266 clocksource_cr16.rating = 0; 267 break; 268 } 269 } 270 271 /* XXX: We may want to mark sched_clock stable here if cr16 clocks are 272 * in sync: 273 * (clocksource_cr16.flags == CLOCK_SOURCE_IS_CONTINUOUS) */ 274 275 /* register at clocksource framework */ 276 clocksource_register_hz(&clocksource_cr16, 277 100 * PAGE0->mem_10msec); 278 279 return 0; 280 } 281 282 device_initcall(init_cr16_clocksource); 283