drivers/clocksource/bcm_kona_timer.c

   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
  37 struct kona_bcm_timers {
  38         int tmr_irq;
  39         void __iomem *tmr_regs;
  40 };
  41
  42 static struct kona_bcm_timers timers;
  43
  44 static u32 arch_timer_rate;
  45
  46 /*
  47  * We use the peripheral timers for system tick, the cpu global timer for
  48  * profile tick
  49  */
  50 static 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
  69 static void
  70 kona_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
 101 static const struct of_device_id bcm_timer_ids[] __initconst = {
 102         {.compatible = "bcm,kona-timer"},
 103         {},
 104 };
 105
 106 static void __init kona_timers_init(struct device_node *node)
 107 {
 108         u32 freq;
 109
 110         if (!of_property_read_u32(node, "clock-frequency", &freq))
 111                 arch_timer_rate = freq;
 112         else
 113                 panic("clock-frequency not set in the .dts file");
 114
 115         /* Setup IRQ numbers */
 116         timers.tmr_irq = irq_of_parse_and_map(node, 0);
 117
 118         /* Setup IO addresses */
 119         timers.tmr_regs = of_iomap(node, 0);
 120
 121         kona_timer_disable_and_clear(timers.tmr_regs);
 122 }
 123
 124 static int kona_timer_set_next_event(unsigned long clc,
 125                                   struct clock_event_device *unused)
 126 {
 127         /*
 128          * timer (0) is disabled by the timer interrupt already
 129          * so, here we reload the next event value and re-enable
 130          * the timer.
 131          *
 132          * This way, we are potentially losing the time between
 133          * timer-interrupt->set_next_event. CPU local timers, when
 134          * they come in should get rid of skew.
 135          */
 136
 137         uint32_t lsw, msw;
 138         uint32_t reg;
 139
 140         kona_timer_get_counter(timers.tmr_regs, &msw, &lsw);
 141
 142         /* Load the "next" event tick value */
 143         writel(lsw + clc, timers.tmr_regs + KONA_GPTIMER_STCM0_OFFSET);
 144
 145         /* Enable compare */
 146         reg = readl(timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
 147         reg |= (1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
 148         writel(reg, timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
 149
 150         return 0;
 151 }
 152
 153 static void kona_timer_set_mode(enum clock_event_mode mode,
 154                              struct clock_event_device *unused)
 155 {
 156         switch (mode) {
 157         case CLOCK_EVT_MODE_ONESHOT:
 158                 /* by default mode is one shot don't do any thing */
 159                 break;
 160         case CLOCK_EVT_MODE_UNUSED:
 161         case CLOCK_EVT_MODE_SHUTDOWN:
 162         default:
 163                 kona_timer_disable_and_clear(timers.tmr_regs);
 164         }
 165 }
 166
 167 static struct clock_event_device kona_clockevent_timer = {
 168         .name = "timer 1",
 169         .features = CLOCK_EVT_FEAT_ONESHOT,
 170         .set_next_event = kona_timer_set_next_event,
 171         .set_mode = kona_timer_set_mode
 172 };
 173
 174 static void __init kona_timer_clockevents_init(void)
 175 {
 176         kona_clockevent_timer.cpumask = cpumask_of(0);
 177         clockevents_config_and_register(&kona_clockevent_timer,
 178                 arch_timer_rate, 6, 0xffffffff);
 179 }
 180
 181 static irqreturn_t kona_timer_interrupt(int irq, void *dev_id)
 182 {
 183         struct clock_event_device *evt = &kona_clockevent_timer;
 184
 185         kona_timer_disable_and_clear(timers.tmr_regs);
 186         evt->event_handler(evt);
 187         return IRQ_HANDLED;
 188 }
 189
 190 static struct irqaction kona_timer_irq = {
 191         .name = "Kona Timer Tick",
 192         .flags = IRQF_TIMER,
 193         .handler = kona_timer_interrupt,
 194 };
 195
 196 static void __init kona_timer_init(struct device_node *node)
 197 {
 198         kona_timers_init(node);
 199         kona_timer_clockevents_init();
 200         setup_irq(timers.tmr_irq, &kona_timer_irq);
 201         kona_timer_set_next_event((arch_timer_rate / HZ), NULL);
 202 }
 203
 204 CLOCKSOURCE_OF_DECLARE(bcm_kona, "bcm,kona-timer", kona_timer_init);