linux/drivers/clocksource/bcm_kona_timer.c
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   1/*
   2 * Copyright (C) 2012 Broadcom Corporation
   3 *
   4 * This program is free software; you can redistribute it and/or
   5 * modify it under the terms of the GNU General Public License as
   6 * published by the Free Software Foundation version 2.
   7 *
   8 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
   9 * kind, whether express or implied; without even the implied warranty
  10 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11 * GNU General Public License for more details.
  12 */
  13
  14#include <linux/init.h>
  15#include <linux/irq.h>
  16#include <linux/interrupt.h>
  17#include <linux/jiffies.h>
  18#include <linux/clockchips.h>
  19#include <linux/types.h>
  20
  21#include <linux/io.h>
  22#include <asm/mach/time.h>
  23
  24#include <linux/of.h>
  25#include <linux/of_address.h>
  26#include <linux/of_irq.h>
  27
  28
  29#define KONA_GPTIMER_STCS_OFFSET                        0x00000000
  30#define KONA_GPTIMER_STCLO_OFFSET                       0x00000004
  31#define KONA_GPTIMER_STCHI_OFFSET                       0x00000008
  32#define KONA_GPTIMER_STCM0_OFFSET                       0x0000000C
  33
  34#define KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT             0
  35#define KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT          4
  36
  37struct kona_bcm_timers {
  38        int tmr_irq;
  39        void __iomem *tmr_regs;
  40};
  41
  42static struct kona_bcm_timers timers;
  43
  44static u32 arch_timer_rate;
  45
  46/*
  47 * We use the peripheral timers for system tick, the cpu global timer for
  48 * profile tick
  49 */
  50static void kona_timer_disable_and_clear(void __iomem *base)
  51{
  52        uint32_t reg;
  53
  54        /*
  55         * clear and disable interrupts
  56         * We are using compare/match register 0 for our system interrupts
  57         */
  58        reg = readl(base + KONA_GPTIMER_STCS_OFFSET);
  59
  60        /* Clear compare (0) interrupt */
  61        reg |= 1 << KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT;
  62        /* disable compare */
  63        reg &= ~(1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
  64
  65        writel(reg, base + KONA_GPTIMER_STCS_OFFSET);
  66
  67}
  68
  69static void
  70kona_timer_get_counter(void *timer_base, uint32_t *msw, uint32_t *lsw)
  71{
  72        void __iomem *base = IOMEM(timer_base);
  73        int loop_limit = 4;
  74
  75        /*
  76         * Read 64-bit free running counter
  77         * 1. Read hi-word
  78         * 2. Read low-word
  79         * 3. Read hi-word again
  80         * 4.1
  81         *      if new hi-word is not equal to previously read hi-word, then
  82         *      start from #1
  83         * 4.2
  84         *      if new hi-word is equal to previously read hi-word then stop.
  85         */
  86
  87        while (--loop_limit) {
  88                *msw = readl(base + KONA_GPTIMER_STCHI_OFFSET);
  89                *lsw = readl(base + KONA_GPTIMER_STCLO_OFFSET);
  90                if (*msw == readl(base + KONA_GPTIMER_STCHI_OFFSET))
  91                        break;
  92        }
  93        if (!loop_limit) {
  94                pr_err("bcm_kona_timer: getting counter failed.\n");
  95                pr_err(" Timer will be impacted\n");
  96        }
  97
  98        return;
  99}
 100
 101static const struct of_device_id bcm_timer_ids[] __initconst = {
 102        {.compatible = "bcm,kona-timer"},
 103        {},
 104};
 105
 106static void __init kona_timers_init(void)
 107{
 108        struct device_node *node;
 109        u32 freq;
 110
 111        node = of_find_matching_node(NULL, bcm_timer_ids);
 112
 113        if (!node)
 114                panic("No timer");
 115
 116        if (!of_property_read_u32(node, "clock-frequency", &freq))
 117                arch_timer_rate = freq;
 118        else
 119                panic("clock-frequency not set in the .dts file");
 120
 121        /* Setup IRQ numbers */
 122        timers.tmr_irq = irq_of_parse_and_map(node, 0);
 123
 124        /* Setup IO addresses */
 125        timers.tmr_regs = of_iomap(node, 0);
 126
 127        kona_timer_disable_and_clear(timers.tmr_regs);
 128}
 129
 130static int kona_timer_set_next_event(unsigned long clc,
 131                                  struct clock_event_device *unused)
 132{
 133        /*
 134         * timer (0) is disabled by the timer interrupt already
 135         * so, here we reload the next event value and re-enable
 136         * the timer.
 137         *
 138         * This way, we are potentially losing the time between
 139         * timer-interrupt->set_next_event. CPU local timers, when
 140         * they come in should get rid of skew.
 141         */
 142
 143        uint32_t lsw, msw;
 144        uint32_t reg;
 145
 146        kona_timer_get_counter(timers.tmr_regs, &msw, &lsw);
 147
 148        /* Load the "next" event tick value */
 149        writel(lsw + clc, timers.tmr_regs + KONA_GPTIMER_STCM0_OFFSET);
 150
 151        /* Enable compare */
 152        reg = readl(timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
 153        reg |= (1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
 154        writel(reg, timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
 155
 156        return 0;
 157}
 158
 159static void kona_timer_set_mode(enum clock_event_mode mode,
 160                             struct clock_event_device *unused)
 161{
 162        switch (mode) {
 163        case CLOCK_EVT_MODE_ONESHOT:
 164                /* by default mode is one shot don't do any thing */
 165                break;
 166        case CLOCK_EVT_MODE_UNUSED:
 167        case CLOCK_EVT_MODE_SHUTDOWN:
 168        default:
 169                kona_timer_disable_and_clear(timers.tmr_regs);
 170        }
 171}
 172
 173static struct clock_event_device kona_clockevent_timer = {
 174        .name = "timer 1",
 175        .features = CLOCK_EVT_FEAT_ONESHOT,
 176        .set_next_event = kona_timer_set_next_event,
 177        .set_mode = kona_timer_set_mode
 178};
 179
 180static void __init kona_timer_clockevents_init(void)
 181{
 182        kona_clockevent_timer.cpumask = cpumask_of(0);
 183        clockevents_config_and_register(&kona_clockevent_timer,
 184                arch_timer_rate, 6, 0xffffffff);
 185}
 186
 187static irqreturn_t kona_timer_interrupt(int irq, void *dev_id)
 188{
 189        struct clock_event_device *evt = &kona_clockevent_timer;
 190
 191        kona_timer_disable_and_clear(timers.tmr_regs);
 192        evt->event_handler(evt);
 193        return IRQ_HANDLED;
 194}
 195
 196static struct irqaction kona_timer_irq = {
 197        .name = "Kona Timer Tick",
 198        .flags = IRQF_TIMER,
 199        .handler = kona_timer_interrupt,
 200};
 201
 202static void __init kona_timer_init(void)
 203{
 204        kona_timers_init();
 205        kona_timer_clockevents_init();
 206        setup_irq(timers.tmr_irq, &kona_timer_irq);
 207        kona_timer_set_next_event((arch_timer_rate / HZ), NULL);
 208}
 209
 210CLOCKSOURCE_OF_DECLARE(bcm_kona, "bcm,kona-timer",
 211        kona_timer_init);
 212
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