arch/openrisc/kernel/time.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * OpenRISC time.c
   4  *
   5  * Linux architectural port borrowing liberally from similar works of
   6  * others.  All original copyrights apply as per the original source
   7  * declaration.
   8  *
   9  * Modifications for the OpenRISC architecture:
  10  * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
  11  */
  12
  13 #include <linux/kernel.h>
  14 #include <linux/time.h>
  15 #include <linux/timex.h>
  16 #include <linux/interrupt.h>
  17 #include <linux/ftrace.h>
  18
  19 #include <linux/clocksource.h>
  20 #include <linux/clockchips.h>
  21 #include <linux/irq.h>
  22 #include <linux/io.h>
  23
  24 #include <asm/cpuinfo.h>
  25
  26 /* Test the timer ticks to count, used in sync routine */
  27 inline void openrisc_timer_set(unsigned long count)
  28 {
  29         mtspr(SPR_TTCR, count);
  30 }
  31
  32 /* Set the timer to trigger in delta cycles */
  33 inline void openrisc_timer_set_next(unsigned long delta)
  34 {
  35         u32 c;
  36
  37         /* Read 32-bit counter value, add delta, mask off the low 28 bits.
  38          * We're guaranteed delta won't be bigger than 28 bits because the
  39          * generic timekeeping code ensures that for us.
  40          */
  41         c = mfspr(SPR_TTCR);
  42         c += delta;
  43         c &= SPR_TTMR_TP;
  44
  45         /* Set counter and enable interrupt.
  46          * Keep timer in continuous mode always.
  47          */
  48         mtspr(SPR_TTMR, SPR_TTMR_CR | SPR_TTMR_IE | c);
  49 }
  50
  51 static int openrisc_timer_set_next_event(unsigned long delta,
  52                                          struct clock_event_device *dev)
  53 {
  54         openrisc_timer_set_next(delta);
  55         return 0;
  56 }
  57
  58 /* This is the clock event device based on the OR1K tick timer.
  59  * As the timer is being used as a continuous clock-source (required for HR
  60  * timers) we cannot enable the PERIODIC feature.  The tick timer can run using
  61  * one-shot events, so no problem.
  62  */
  63 DEFINE_PER_CPU(struct clock_event_device, clockevent_openrisc_timer);
  64
  65 void openrisc_clockevent_init(void)
  66 {
  67         unsigned int cpu = smp_processor_id();
  68         struct clock_event_device *evt =
  69                 &per_cpu(clockevent_openrisc_timer, cpu);
  70         struct cpuinfo_or1k *cpuinfo = &cpuinfo_or1k[cpu];
  71
  72         mtspr(SPR_TTMR, SPR_TTMR_CR);
  73
  74 #ifdef CONFIG_SMP
  75         evt->broadcast = tick_broadcast;
  76 #endif
  77         evt->name = "openrisc_timer_clockevent",
  78         evt->features = CLOCK_EVT_FEAT_ONESHOT,
  79         evt->rating = 300,
  80         evt->set_next_event = openrisc_timer_set_next_event,
  81
  82         evt->cpumask = cpumask_of(cpu);
  83
  84         /* We only have 28 bits */
  85         clockevents_config_and_register(evt, cpuinfo->clock_frequency,
  86                                         100, 0x0fffffff);
  87
  88 }
  89
  90 static inline void timer_ack(void)
  91 {
  92         /* Clear the IP bit and disable further interrupts */
  93         /* This can be done very simply... we just need to keep the timer
  94            running, so just maintain the CR bits while clearing the rest
  95            of the register
  96          */
  97         mtspr(SPR_TTMR, SPR_TTMR_CR);
  98 }
  99
 100 /*
 101  * The timer interrupt is mostly handled in generic code nowadays... this
 102  * function just acknowledges the interrupt and fires the event handler that
 103  * has been set on the clockevent device by the generic time management code.
 104  *
 105  * This function needs to be called by the timer exception handler and that's
 106  * all the exception handler needs to do.
 107  */
 108
 109 irqreturn_t __irq_entry timer_interrupt(struct pt_regs *regs)
 110 {
 111         struct pt_regs *old_regs = set_irq_regs(regs);
 112         unsigned int cpu = smp_processor_id();
 113         struct clock_event_device *evt =
 114                 &per_cpu(clockevent_openrisc_timer, cpu);
 115
 116         timer_ack();
 117
 118         /*
 119          * update_process_times() expects us to have called irq_enter().
 120          */
 121         irq_enter();
 122         evt->event_handler(evt);
 123         irq_exit();
 124
 125         set_irq_regs(old_regs);
 126
 127         return IRQ_HANDLED;
 128 }
 129
 130 /**
 131  * Clocksource: Based on OpenRISC timer/counter
 132  *
 133  * This sets up the OpenRISC Tick Timer as a clock source.  The tick timer
 134  * is 32 bits wide and runs at the CPU clock frequency.
 135  */
 136 static u64 openrisc_timer_read(struct clocksource *cs)
 137 {
 138         return (u64) mfspr(SPR_TTCR);
 139 }
 140
 141 static struct clocksource openrisc_timer = {
 142         .name = "openrisc_timer",
 143         .rating = 200,
 144         .read = openrisc_timer_read,
 145         .mask = CLOCKSOURCE_MASK(32),
 146         .flags = CLOCK_SOURCE_IS_CONTINUOUS,
 147 };
 148
 149 static int __init openrisc_timer_init(void)
 150 {
 151         struct cpuinfo_or1k *cpuinfo = &cpuinfo_or1k[smp_processor_id()];
 152
 153         if (clocksource_register_hz(&openrisc_timer, cpuinfo->clock_frequency))
 154                 panic("failed to register clocksource");
 155
 156         /* Enable the incrementer: 'continuous' mode with interrupt disabled */
 157         mtspr(SPR_TTMR, SPR_TTMR_CR);
 158
 159         return 0;
 160 }
 161
 162 void __init time_init(void)
 163 {
 164         u32 upr;
 165
 166         upr = mfspr(SPR_UPR);
 167         if (!(upr & SPR_UPR_TTP))
 168                 panic("Linux not supported on devices without tick timer");
 169
 170         openrisc_timer_init();
 171         openrisc_clockevent_init();
 172 }