LXR linux/drivers/clocksource/bcm_kona

   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#include <linux/clk.h>
  21
  22#include <linux/io.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 int
  70kona_timer_get_counter(void __iomem *timer_base, uint32_t *msw, uint32_t *lsw)
  71{
  72        int loop_limit = 3;
  73
  74        /*
  75         * Read 64-bit free running counter
  76         * 1. Read hi-word
  77         * 2. Read low-word
  78         * 3. Read hi-word again
  79         * 4.1
  80         *      if new hi-word is not equal to previously read hi-word, then
  81         *      start from #1
  82         * 4.2
  83         *      if new hi-word is equal to previously read hi-word then stop.
  84         */
  85
  86        do {
  87                *msw = readl(timer_base + KONA_GPTIMER_STCHI_OFFSET);
  88                *lsw = readl(timer_base + KONA_GPTIMER_STCLO_OFFSET);
  89                if (*msw == readl(timer_base + KONA_GPTIMER_STCHI_OFFSET))
  90                        break;
  91        } while (--loop_limit);
  92        if (!loop_limit) {
  93                pr_err("bcm_kona_timer: getting counter failed.\n");
  94                pr_err(" Timer will be impacted\n");
  95                return -ETIMEDOUT;
  96        }
  97
  98        return 0;
  99}
 100
 101static int kona_timer_set_next_event(unsigned long clc,
 102                                  struct clock_event_device *unused)
 103{
 104        /*
 105         * timer (0) is disabled by the timer interrupt already
 106         * so, here we reload the next event value and re-enable
 107         * the timer.
 108         *
 109         * This way, we are potentially losing the time between
 110         * timer-interrupt->set_next_event. CPU local timers, when
 111         * they come in should get rid of skew.
 112         */
 113
 114        uint32_t lsw, msw;
 115        uint32_t reg;
 116        int ret;
 117
 118        ret = kona_timer_get_counter(timers.tmr_regs, &msw, &lsw);
 119        if (ret)
 120                return ret;
 121
 122        /* Load the "next" event tick value */
 123        writel(lsw + clc, timers.tmr_regs + KONA_GPTIMER_STCM0_OFFSET);
 124
 125        /* Enable compare */
 126        reg = readl(timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
 127        reg |= (1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
 128        writel(reg, timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
 129
 130        return 0;
 131}
 132
 133static int kona_timer_shutdown(struct clock_event_device *evt)
 134{
 135        kona_timer_disable_and_clear(timers.tmr_regs);
 136        return 0;
 137}
 138
 139static struct clock_event_device kona_clockevent_timer = {
 140        .name = "timer 1",
 141        .features = CLOCK_EVT_FEAT_ONESHOT,
 142        .set_next_event = kona_timer_set_next_event,
 143        .set_state_shutdown = kona_timer_shutdown,
 144        .tick_resume = kona_timer_shutdown,
 145};
 146
 147static void __init kona_timer_clockevents_init(void)
 148{
 149        kona_clockevent_timer.cpumask = cpumask_of(0);
 150        clockevents_config_and_register(&kona_clockevent_timer,
 151                arch_timer_rate, 6, 0xffffffff);
 152}
 153
 154static irqreturn_t kona_timer_interrupt(int irq, void *dev_id)
 155{
 156        struct clock_event_device *evt = &kona_clockevent_timer;
 157
 158        kona_timer_disable_and_clear(timers.tmr_regs);
 159        evt->event_handler(evt);
 160        return IRQ_HANDLED;
 161}
 162
 163static int __init kona_timer_init(struct device_node *node)
 164{
 165        u32 freq;
 166        struct clk *external_clk;
 167
 168        external_clk = of_clk_get_by_name(node, NULL);
 169
 170        if (!IS_ERR(external_clk)) {
 171                arch_timer_rate = clk_get_rate(external_clk);
 172                clk_prepare_enable(external_clk);
 173        } else if (!of_property_read_u32(node, "clock-frequency", &freq)) {
 174                arch_timer_rate = freq;
 175        } else {
 176                pr_err("Kona Timer v1 unable to determine clock-frequency\n");
 177                return -EINVAL;
 178        }
 179
 180        /* Setup IRQ numbers */
 181        timers.tmr_irq = irq_of_parse_and_map(node, 0);
 182
 183        /* Setup IO addresses */
 184        timers.tmr_regs = of_iomap(node, 0);
 185
 186        kona_timer_disable_and_clear(timers.tmr_regs);
 187
 188        kona_timer_clockevents_init();
 189        if (request_irq(timers.tmr_irq, kona_timer_interrupt, IRQF_TIMER,
 190                        "Kona Timer Tick", NULL))
 191                pr_err("%s: request_irq() failed\n", "Kona Timer Tick");
 192        kona_timer_set_next_event((arch_timer_rate / HZ), NULL);
 193
 194        return 0;
 195}
 196
 197TIMER_OF_DECLARE(brcm_kona, "brcm,kona-timer", kona_timer_init);
 198/*
 199 * bcm,kona-timer is deprecated by brcm,kona-timer
 200 * being kept here for driver compatibility
 201 */
 202TIMER_OF_DECLARE(bcm_kona, "bcm,kona-timer", kona_timer_init);
 203