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 #include <linux/of_clk.h>
  24
  25 #include <asm/cpuinfo.h>
  26 #include <asm/time.h>
  27
  28 irqreturn_t __irq_entry timer_interrupt(struct pt_regs *regs);
  29
  30 /* Test the timer ticks to count, used in sync routine */
  31 inline void openrisc_timer_set(unsigned long count)
  32 {
  33         mtspr(SPR_TTCR, count);
  34 }
  35
  36 /* Set the timer to trigger in delta cycles */
  37 inline void openrisc_timer_set_next(unsigned long delta)
  38 {
  39         u32 c;
  40
  41         /* Read 32-bit counter value, add delta, mask off the low 28 bits.
  42          * We're guaranteed delta won't be bigger than 28 bits because the
  43          * generic timekeeping code ensures that for us.
  44          */
  45         c = mfspr(SPR_TTCR);
  46         c += delta;
  47         c &= SPR_TTMR_TP;
  48
  49         /* Set counter and enable interrupt.
  50          * Keep timer in continuous mode always.
  51          */
  52         mtspr(SPR_TTMR, SPR_TTMR_CR | SPR_TTMR_IE | c);
  53 }
  54
  55 static int openrisc_timer_set_next_event(unsigned long delta,
  56                                          struct clock_event_device *dev)
  57 {
  58         openrisc_timer_set_next(delta);
  59         return 0;
  60 }
  61
  62 /* This is the clock event device based on the OR1K tick timer.
  63  * As the timer is being used as a continuous clock-source (required for HR
  64  * timers) we cannot enable the PERIODIC feature.  The tick timer can run using
  65  * one-shot events, so no problem.
  66  */
  67 static DEFINE_PER_CPU(struct clock_event_device, clockevent_openrisc_timer);
  68
  69 void openrisc_clockevent_init(void)
  70 {
  71         unsigned int cpu = smp_processor_id();
  72         struct clock_event_device *evt =
  73                 &per_cpu(clockevent_openrisc_timer, cpu);
  74         struct cpuinfo_or1k *cpuinfo = &cpuinfo_or1k[cpu];
  75
  76         mtspr(SPR_TTMR, SPR_TTMR_CR);
  77
  78 #ifdef CONFIG_SMP
  79         evt->broadcast = tick_broadcast;
  80 #endif
  81         evt->name = "openrisc_timer_clockevent",
  82         evt->features = CLOCK_EVT_FEAT_ONESHOT,
  83         evt->rating = 300,
  84         evt->set_next_event = openrisc_timer_set_next_event,
  85
  86         evt->cpumask = cpumask_of(cpu);
  87
  88         /* We only have 28 bits */
  89         clockevents_config_and_register(evt, cpuinfo->clock_frequency,
  90                                         100, 0x0fffffff);
  91
  92 }
  93
  94 static inline void timer_ack(void)
  95 {
  96         /* Clear the IP bit and disable further interrupts */
  97         /* This can be done very simply... we just need to keep the timer
  98            running, so just maintain the CR bits while clearing the rest
  99            of the register
 100          */
 101         mtspr(SPR_TTMR, SPR_TTMR_CR);
 102 }
 103
 104 /*
 105  * The timer interrupt is mostly handled in generic code nowadays... this
 106  * function just acknowledges the interrupt and fires the event handler that
 107  * has been set on the clockevent device by the generic time management code.
 108  *
 109  * This function needs to be called by the timer exception handler and that's
 110  * all the exception handler needs to do.
 111  */
 112
 113 irqreturn_t __irq_entry timer_interrupt(struct pt_regs *regs)
 114 {
 115         struct pt_regs *old_regs = set_irq_regs(regs);
 116         unsigned int cpu = smp_processor_id();
 117         struct clock_event_device *evt =
 118                 &per_cpu(clockevent_openrisc_timer, cpu);
 119
 120         timer_ack();
 121
 122         /*
 123          * update_process_times() expects us to have called irq_enter().
 124          */
 125         irq_enter();
 126         evt->event_handler(evt);
 127         irq_exit();
 128
 129         set_irq_regs(old_regs);
 130
 131         return IRQ_HANDLED;
 132 }
 133
 134 /*
 135  * Clocksource: Based on OpenRISC timer/counter
 136  *
 137  * This sets up the OpenRISC Tick Timer as a clock source.  The tick timer
 138  * is 32 bits wide and runs at the CPU clock frequency.
 139  */
 140 static u64 openrisc_timer_read(struct clocksource *cs)
 141 {
 142         return (u64) mfspr(SPR_TTCR);
 143 }
 144
 145 static struct clocksource openrisc_timer = {
 146         .name = "openrisc_timer",
 147         .rating = 200,
 148         .read = openrisc_timer_read,
 149         .mask = CLOCKSOURCE_MASK(32),
 150         .flags = CLOCK_SOURCE_IS_CONTINUOUS,
 151 };
 152
 153 static int __init openrisc_timer_init(void)
 154 {
 155         struct cpuinfo_or1k *cpuinfo = &cpuinfo_or1k[smp_processor_id()];
 156
 157         if (clocksource_register_hz(&openrisc_timer, cpuinfo->clock_frequency))
 158                 panic("failed to register clocksource");
 159
 160         /* Enable the incrementer: 'continuous' mode with interrupt disabled */
 161         mtspr(SPR_TTMR, SPR_TTMR_CR);
 162
 163         return 0;
 164 }
 165
 166 void __init time_init(void)
 167 {
 168         u32 upr;
 169
 170         upr = mfspr(SPR_UPR);
 171         if (!(upr & SPR_UPR_TTP))
 172                 panic("Linux not supported on devices without tick timer");
 173
 174         openrisc_timer_init();
 175         openrisc_clockevent_init();
 176
 177         of_clk_init(NULL);
 178         timer_probe();
 179 }