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  * All RISC-V systems have a timer attached to every hart.  These timers can
   7  * either be read from the "time" and "timeh" CSRs, and can use the SBI to
   8  * setup events, or directly accessed using MMIO registers.
   9  */
  10 #include <linux/clocksource.h>
  11 #include <linux/clockchips.h>
  12 #include <linux/cpu.h>
  13 #include <linux/delay.h>
  14 #include <linux/irq.h>
  15 #include <linux/sched_clock.h>
  16 #include <linux/io-64-nonatomic-lo-hi.h>
  17 #include <asm/smp.h>
  18 #include <asm/sbi.h>
  19
  20 u64 __iomem *riscv_time_cmp;
  21 u64 __iomem *riscv_time_val;
  22
  23 static inline void mmio_set_timer(u64 val)
  24 {
  25         void __iomem *r;
  26
  27         r = riscv_time_cmp + cpuid_to_hartid_map(smp_processor_id());
  28         writeq_relaxed(val, r);
  29 }
  30
  31 static int riscv_clock_next_event(unsigned long delta,
  32                 struct clock_event_device *ce)
  33 {
  34         csr_set(CSR_IE, IE_TIE);
  35         if (IS_ENABLED(CONFIG_RISCV_SBI))
  36                 sbi_set_timer(get_cycles64() + delta);
  37         else
  38                 mmio_set_timer(get_cycles64() + delta);
  39         return 0;
  40 }
  41
  42 static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = {
  43         .name                   = "riscv_timer_clockevent",
  44         .features               = CLOCK_EVT_FEAT_ONESHOT,
  45         .rating                 = 100,
  46         .set_next_event         = riscv_clock_next_event,
  47 };
  48
  49 /*
  50  * It is guaranteed that all the timers across all the harts are synchronized
  51  * within one tick of each other, so while this could technically go
  52  * backwards when hopping between CPUs, practically it won't happen.
  53  */
  54 static unsigned long long riscv_clocksource_rdtime(struct clocksource *cs)
  55 {
  56         return get_cycles64();
  57 }
  58
  59 static u64 riscv_sched_clock(void)
  60 {
  61         return get_cycles64();
  62 }
  63
  64 static struct clocksource riscv_clocksource = {
  65         .name           = "riscv_clocksource",
  66         .rating         = 300,
  67         .mask           = CLOCKSOURCE_MASK(64),
  68         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  69         .read           = riscv_clocksource_rdtime,
  70 };
  71
  72 static int riscv_timer_starting_cpu(unsigned int cpu)
  73 {
  74         struct clock_event_device *ce = per_cpu_ptr(&riscv_clock_event, cpu);
  75
  76         ce->cpumask = cpumask_of(cpu);
  77         clockevents_config_and_register(ce, riscv_timebase, 100, 0x7fffffff);
  78
  79         csr_set(CSR_IE, IE_TIE);
  80         return 0;
  81 }
  82
  83 static int riscv_timer_dying_cpu(unsigned int cpu)
  84 {
  85         csr_clear(CSR_IE, IE_TIE);
  86         return 0;
  87 }
  88
  89 /* called directly from the low-level interrupt handler */
  90 void riscv_timer_interrupt(void)
  91 {
  92         struct clock_event_device *evdev = this_cpu_ptr(&riscv_clock_event);
  93
  94         csr_clear(CSR_IE, IE_TIE);
  95         evdev->event_handler(evdev);
  96 }
  97
  98 static int __init riscv_timer_init_dt(struct device_node *n)
  99 {
 100         int cpuid, hartid, error;
 101
 102         hartid = riscv_of_processor_hartid(n);
 103         if (hartid < 0) {
 104                 pr_warn("Not valid hartid for node [%pOF] error = [%d]\n",
 105                         n, hartid);
 106                 return hartid;
 107         }
 108
 109         cpuid = riscv_hartid_to_cpuid(hartid);
 110         if (cpuid < 0) {
 111                 pr_warn("Invalid cpuid for hartid [%d]\n", hartid);
 112                 return cpuid;
 113         }
 114
 115         if (cpuid != smp_processor_id())
 116                 return 0;
 117
 118         pr_info("%s: Registering clocksource cpuid [%d] hartid [%d]\n",
 119                __func__, cpuid, hartid);
 120         error = clocksource_register_hz(&riscv_clocksource, riscv_timebase);
 121         if (error) {
 122                 pr_err("RISCV timer register failed [%d] for cpu = [%d]\n",
 123                        error, cpuid);
 124                 return error;
 125         }
 126
 127         sched_clock_register(riscv_sched_clock, 64, riscv_timebase);
 128
 129         error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
 130                          "clockevents/riscv/timer:starting",
 131                          riscv_timer_starting_cpu, riscv_timer_dying_cpu);
 132         if (error)
 133                 pr_err("cpu hp setup state failed for RISCV timer [%d]\n",
 134                        error);
 135         return error;
 136 }
 137
 138 TIMER_OF_DECLARE(riscv_timer, "riscv", riscv_timer_init_dt);