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 = "brcm,kona-timer"},
 103         {.compatible = "bcm,kona-timer"}, /* deprecated name */
 104         {},
 105 };
 106
 107 static void __init kona_timers_init(struct device_node *node)
 108 {
 109         u32 freq;
 110
 111         if (!of_property_read_u32(node, "clock-frequency", &freq))
 112                 arch_timer_rate = freq;
 113         else
 114                 panic("clock-frequency not set in the .dts file");
 115
 116         /* Setup IRQ numbers */
 117         timers.tmr_irq = irq_of_parse_and_map(node, 0);
 118
 119         /* Setup IO addresses */
 120         timers.tmr_regs = of_iomap(node, 0);
 121
 122         kona_timer_disable_and_clear(timers.tmr_regs);
 123 }
 124
 125 static int kona_timer_set_next_event(unsigned long clc,
 126                                   struct clock_event_device *unused)
 127 {
 128         /*
 129          * timer (0) is disabled by the timer interrupt already
 130          * so, here we reload the next event value and re-enable
 131          * the timer.
 132          *
 133          * This way, we are potentially losing the time between
 134          * timer-interrupt->set_next_event. CPU local timers, when
 135          * they come in should get rid of skew.
 136          */
 137
 138         uint32_t lsw, msw;
 139         uint32_t reg;
 140
 141         kona_timer_get_counter(timers.tmr_regs, &msw, &lsw);
 142
 143         /* Load the "next" event tick value */
 144         writel(lsw + clc, timers.tmr_regs + KONA_GPTIMER_STCM0_OFFSET);
 145
 146         /* Enable compare */
 147         reg = readl(timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
 148         reg |= (1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
 149         writel(reg, timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
 150
 151         return 0;
 152 }
 153
 154 static void kona_timer_set_mode(enum clock_event_mode mode,
 155                              struct clock_event_device *unused)
 156 {
 157         switch (mode) {
 158         case CLOCK_EVT_MODE_ONESHOT:
 159                 /* by default mode is one shot don't do any thing */
 160                 break;
 161         case CLOCK_EVT_MODE_UNUSED:
 162         case CLOCK_EVT_MODE_SHUTDOWN:
 163         default:
 164                 kona_timer_disable_and_clear(timers.tmr_regs);
 165         }
 166 }
 167
 168 static struct clock_event_device kona_clockevent_timer = {
 169         .name = "timer 1",
 170         .features = CLOCK_EVT_FEAT_ONESHOT,
 171         .set_next_event = kona_timer_set_next_event,
 172         .set_mode = kona_timer_set_mode
 173 };
 174
 175 static void __init kona_timer_clockevents_init(void)
 176 {
 177         kona_clockevent_timer.cpumask = cpumask_of(0);
 178         clockevents_config_and_register(&kona_clockevent_timer,
 179                 arch_timer_rate, 6, 0xffffffff);
 180 }
 181
 182 static irqreturn_t kona_timer_interrupt(int irq, void *dev_id)
 183 {
 184         struct clock_event_device *evt = &kona_clockevent_timer;
 185
 186         kona_timer_disable_and_clear(timers.tmr_regs);
 187         evt->event_handler(evt);
 188         return IRQ_HANDLED;
 189 }
 190
 191 static struct irqaction kona_timer_irq = {
 192         .name = "Kona Timer Tick",
 193         .flags = IRQF_TIMER,
 194         .handler = kona_timer_interrupt,
 195 };
 196
 197 static void __init kona_timer_init(struct device_node *node)
 198 {
 199         kona_timers_init(node);
 200         kona_timer_clockevents_init();
 201         setup_irq(timers.tmr_irq, &kona_timer_irq);
 202         kona_timer_set_next_event((arch_timer_rate / HZ), NULL);
 203 }
 204
 205 CLOCKSOURCE_OF_DECLARE(brcm_kona, "brcm,kona-timer", kona_timer_init);
 206 /*
 207  * bcm,kona-timer is deprecated by brcm,kona-timer
 208  * being kept here for driver compatibility
 209  */
 210 CLOCKSOURCE_OF_DECLARE(bcm_kona, "bcm,kona-timer", kona_timer_init);