drivers/clocksource/timer-riscv.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2012 Regents of the University of California
   4  * Copyright (C) 2017 SiFive
   5  */
   6 #include <linux/clocksource.h>
   7 #include <linux/clockchips.h>
   8 #include <linux/cpu.h>
   9 #include <linux/delay.h>
  10 #include <linux/irq.h>
  11 #include <linux/sched_clock.h>
  12 #include <asm/smp.h>
  13 #include <asm/sbi.h>
  14
  15 /*
  16  * All RISC-V systems have a timer attached to every hart.  These timers can be
  17  * read by the 'rdcycle' pseudo instruction, and can use the SBI to setup
  18  * events.  In order to abstract the architecture-specific timer reading and
  19  * setting functions away from the clock event insertion code, we provide
  20  * function pointers to the clockevent subsystem that perform two basic
  21  * operations: rdtime() reads the timer on the current CPU, and
  22  * next_event(delta) sets the next timer event to 'delta' cycles in the future.
  23  * As the timers are inherently a per-cpu resource, these callbacks perform
  24  * operations on the current hart.  There is guaranteed to be exactly one timer
  25  * per hart on all RISC-V systems.
  26  */
  27
  28 static int riscv_clock_next_event(unsigned long delta,
  29                 struct clock_event_device *ce)
  30 {
  31         csr_set(sie, SIE_STIE);
  32         sbi_set_timer(get_cycles64() + delta);
  33         return 0;
  34 }
  35
  36 static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = {
  37         .name                   = "riscv_timer_clockevent",
  38         .features               = CLOCK_EVT_FEAT_ONESHOT,
  39         .rating                 = 100,
  40         .set_next_event         = riscv_clock_next_event,
  41 };
  42
  43 /*
  44  * It is guaranteed that all the timers across all the harts are synchronized
  45  * within one tick of each other, so while this could technically go
  46  * backwards when hopping between CPUs, practically it won't happen.
  47  */
  48 static unsigned long long riscv_clocksource_rdtime(struct clocksource *cs)
  49 {
  50         return get_cycles64();
  51 }
  52
  53 static u64 riscv_sched_clock(void)
  54 {
  55         return get_cycles64();
  56 }
  57
  58 static DEFINE_PER_CPU(struct clocksource, riscv_clocksource) = {
  59         .name           = "riscv_clocksource",
  60         .rating         = 300,
  61         .mask           = CLOCKSOURCE_MASK(BITS_PER_LONG),
  62         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  63         .read           = riscv_clocksource_rdtime,
  64 };
  65
  66 static int riscv_timer_starting_cpu(unsigned int cpu)
  67 {
  68         struct clock_event_device *ce = per_cpu_ptr(&riscv_clock_event, cpu);
  69
  70         ce->cpumask = cpumask_of(cpu);
  71         clockevents_config_and_register(ce, riscv_timebase, 100, 0x7fffffff);
  72
  73         csr_set(sie, SIE_STIE);
  74         return 0;
  75 }
  76
  77 static int riscv_timer_dying_cpu(unsigned int cpu)
  78 {
  79         csr_clear(sie, SIE_STIE);
  80         return 0;
  81 }
  82
  83 /* called directly from the low-level interrupt handler */
  84 void riscv_timer_interrupt(void)
  85 {
  86         struct clock_event_device *evdev = this_cpu_ptr(&riscv_clock_event);
  87
  88         csr_clear(sie, SIE_STIE);
  89         evdev->event_handler(evdev);
  90 }
  91
  92 static int __init riscv_timer_init_dt(struct device_node *n)
  93 {
  94         int cpuid, hartid, error;
  95         struct clocksource *cs;
  96
  97         hartid = riscv_of_processor_hartid(n);
  98         if (hartid < 0) {
  99                 pr_warn("Not valid hartid for node [%pOF] error = [%d]\n",
 100                         n, hartid);
 101                 return hartid;
 102         }
 103
 104         cpuid = riscv_hartid_to_cpuid(hartid);
 105         if (cpuid < 0) {
 106                 pr_warn("Invalid cpuid for hartid [%d]\n", hartid);
 107                 return cpuid;
 108         }
 109
 110         if (cpuid != smp_processor_id())
 111                 return 0;
 112
 113         pr_info("%s: Registering clocksource cpuid [%d] hartid [%d]\n",
 114                __func__, cpuid, hartid);
 115         cs = per_cpu_ptr(&riscv_clocksource, cpuid);
 116         error = clocksource_register_hz(cs, riscv_timebase);
 117         if (error) {
 118                 pr_err("RISCV timer register failed [%d] for cpu = [%d]\n",
 119                        error, cpuid);
 120                 return error;
 121         }
 122
 123         sched_clock_register(riscv_sched_clock,
 124                         BITS_PER_LONG, riscv_timebase);
 125
 126         error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
 127                          "clockevents/riscv/timer:starting",
 128                          riscv_timer_starting_cpu, riscv_timer_dying_cpu);
 129         if (error)
 130                 pr_err("cpu hp setup state failed for RISCV timer [%d]\n",
 131                        error);
 132         return error;
 133 }
 134
 135 TIMER_OF_DECLARE(riscv_timer, "riscv", riscv_timer_init_dt);