drivers/clocksource/bcm_kona_timer.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 // Copyright (C) 2012 Broadcom Corporation
   3
   4 #include <linux/init.h>
   5 #include <linux/irq.h>
   6 #include <linux/interrupt.h>
   7 #include <linux/jiffies.h>
   8 #include <linux/clockchips.h>
   9 #include <linux/types.h>
  10 #include <linux/clk.h>
  11
  12 #include <linux/io.h>
  13
  14 #include <linux/of.h>
  15 #include <linux/of_address.h>
  16 #include <linux/of_irq.h>
  17
  18
  19 #define KONA_GPTIMER_STCS_OFFSET                        0x00000000
  20 #define KONA_GPTIMER_STCLO_OFFSET                       0x00000004
  21 #define KONA_GPTIMER_STCHI_OFFSET                       0x00000008
  22 #define KONA_GPTIMER_STCM0_OFFSET                       0x0000000C
  23
  24 #define KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT             0
  25 #define KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT          4
  26
  27 struct kona_bcm_timers {
  28         int tmr_irq;
  29         void __iomem *tmr_regs;
  30 };
  31
  32 static struct kona_bcm_timers timers;
  33
  34 static u32 arch_timer_rate;
  35
  36 /*
  37  * We use the peripheral timers for system tick, the cpu global timer for
  38  * profile tick
  39  */
  40 static void kona_timer_disable_and_clear(void __iomem *base)
  41 {
  42         uint32_t reg;
  43
  44         /*
  45          * clear and disable interrupts
  46          * We are using compare/match register 0 for our system interrupts
  47          */
  48         reg = readl(base + KONA_GPTIMER_STCS_OFFSET);
  49
  50         /* Clear compare (0) interrupt */
  51         reg |= 1 << KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT;
  52         /* disable compare */
  53         reg &= ~(1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
  54
  55         writel(reg, base + KONA_GPTIMER_STCS_OFFSET);
  56
  57 }
  58
  59 static int
  60 kona_timer_get_counter(void __iomem *timer_base, uint32_t *msw, uint32_t *lsw)
  61 {
  62         int loop_limit = 3;
  63
  64         /*
  65          * Read 64-bit free running counter
  66          * 1. Read hi-word
  67          * 2. Read low-word
  68          * 3. Read hi-word again
  69          * 4.1
  70          *      if new hi-word is not equal to previously read hi-word, then
  71          *      start from #1
  72          * 4.2
  73          *      if new hi-word is equal to previously read hi-word then stop.
  74          */
  75
  76         do {
  77                 *msw = readl(timer_base + KONA_GPTIMER_STCHI_OFFSET);
  78                 *lsw = readl(timer_base + KONA_GPTIMER_STCLO_OFFSET);
  79                 if (*msw == readl(timer_base + KONA_GPTIMER_STCHI_OFFSET))
  80                         break;
  81         } while (--loop_limit);
  82         if (!loop_limit) {
  83                 pr_err("bcm_kona_timer: getting counter failed.\n");
  84                 pr_err(" Timer will be impacted\n");
  85                 return -ETIMEDOUT;
  86         }
  87
  88         return 0;
  89 }
  90
  91 static int kona_timer_set_next_event(unsigned long clc,
  92                                   struct clock_event_device *unused)
  93 {
  94         /*
  95          * timer (0) is disabled by the timer interrupt already
  96          * so, here we reload the next event value and re-enable
  97          * the timer.
  98          *
  99          * This way, we are potentially losing the time between
 100          * timer-interrupt->set_next_event. CPU local timers, when
 101          * they come in should get rid of skew.
 102          */
 103
 104         uint32_t lsw, msw;
 105         uint32_t reg;
 106         int ret;
 107
 108         ret = kona_timer_get_counter(timers.tmr_regs, &msw, &lsw);
 109         if (ret)
 110                 return ret;
 111
 112         /* Load the "next" event tick value */
 113         writel(lsw + clc, timers.tmr_regs + KONA_GPTIMER_STCM0_OFFSET);
 114
 115         /* Enable compare */
 116         reg = readl(timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
 117         reg |= (1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
 118         writel(reg, timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
 119
 120         return 0;
 121 }
 122
 123 static int kona_timer_shutdown(struct clock_event_device *evt)
 124 {
 125         kona_timer_disable_and_clear(timers.tmr_regs);
 126         return 0;
 127 }
 128
 129 static struct clock_event_device kona_clockevent_timer = {
 130         .name = "timer 1",
 131         .features = CLOCK_EVT_FEAT_ONESHOT,
 132         .set_next_event = kona_timer_set_next_event,
 133         .set_state_shutdown = kona_timer_shutdown,
 134         .tick_resume = kona_timer_shutdown,
 135 };
 136
 137 static void __init kona_timer_clockevents_init(void)
 138 {
 139         kona_clockevent_timer.cpumask = cpumask_of(0);
 140         clockevents_config_and_register(&kona_clockevent_timer,
 141                 arch_timer_rate, 6, 0xffffffff);
 142 }
 143
 144 static irqreturn_t kona_timer_interrupt(int irq, void *dev_id)
 145 {
 146         struct clock_event_device *evt = &kona_clockevent_timer;
 147
 148         kona_timer_disable_and_clear(timers.tmr_regs);
 149         evt->event_handler(evt);
 150         return IRQ_HANDLED;
 151 }
 152
 153 static int __init kona_timer_init(struct device_node *node)
 154 {
 155         u32 freq;
 156         struct clk *external_clk;
 157
 158         external_clk = of_clk_get_by_name(node, NULL);
 159
 160         if (!IS_ERR(external_clk)) {
 161                 arch_timer_rate = clk_get_rate(external_clk);
 162                 clk_prepare_enable(external_clk);
 163         } else if (!of_property_read_u32(node, "clock-frequency", &freq)) {
 164                 arch_timer_rate = freq;
 165         } else {
 166                 pr_err("Kona Timer v1 unable to determine clock-frequency\n");
 167                 return -EINVAL;
 168         }
 169
 170         /* Setup IRQ numbers */
 171         timers.tmr_irq = irq_of_parse_and_map(node, 0);
 172
 173         /* Setup IO addresses */
 174         timers.tmr_regs = of_iomap(node, 0);
 175
 176         kona_timer_disable_and_clear(timers.tmr_regs);
 177
 178         kona_timer_clockevents_init();
 179         if (request_irq(timers.tmr_irq, kona_timer_interrupt, IRQF_TIMER,
 180                         "Kona Timer Tick", NULL))
 181                 pr_err("%s: request_irq() failed\n", "Kona Timer Tick");
 182         kona_timer_set_next_event((arch_timer_rate / HZ), NULL);
 183
 184         return 0;
 185 }
 186
 187 TIMER_OF_DECLARE(brcm_kona, "brcm,kona-timer", kona_timer_init);
 188 /*
 189  * bcm,kona-timer is deprecated by brcm,kona-timer
 190  * being kept here for driver compatibility
 191  */
 192 TIMER_OF_DECLARE(bcm_kona, "bcm,kona-timer", kona_timer_init);