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 #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
  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 __iomem *timer_base, uint32_t *msw, uint32_t *lsw)
  71 {
  72         int loop_limit = 4;
  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         while (--loop_limit) {
  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         }
  92         if (!loop_limit) {
  93                 pr_err("bcm_kona_timer: getting counter failed.\n");
  94                 pr_err(" Timer will be impacted\n");
  95         }
  96
  97         return;
  98 }
  99
 100 static int kona_timer_set_next_event(unsigned long clc,
 101                                   struct clock_event_device *unused)
 102 {
 103         /*
 104          * timer (0) is disabled by the timer interrupt already
 105          * so, here we reload the next event value and re-enable
 106          * the timer.
 107          *
 108          * This way, we are potentially losing the time between
 109          * timer-interrupt->set_next_event. CPU local timers, when
 110          * they come in should get rid of skew.
 111          */
 112
 113         uint32_t lsw, msw;
 114         uint32_t reg;
 115
 116         kona_timer_get_counter(timers.tmr_regs, &msw, &lsw);
 117
 118         /* Load the "next" event tick value */
 119         writel(lsw + clc, timers.tmr_regs + KONA_GPTIMER_STCM0_OFFSET);
 120
 121         /* Enable compare */
 122         reg = readl(timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
 123         reg |= (1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
 124         writel(reg, timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
 125
 126         return 0;
 127 }
 128
 129 static int kona_timer_shutdown(struct clock_event_device *evt)
 130 {
 131         kona_timer_disable_and_clear(timers.tmr_regs);
 132         return 0;
 133 }
 134
 135 static struct clock_event_device kona_clockevent_timer = {
 136         .name = "timer 1",
 137         .features = CLOCK_EVT_FEAT_ONESHOT,
 138         .set_next_event = kona_timer_set_next_event,
 139         .set_state_shutdown = kona_timer_shutdown,
 140         .tick_resume = kona_timer_shutdown,
 141 };
 142
 143 static void __init kona_timer_clockevents_init(void)
 144 {
 145         kona_clockevent_timer.cpumask = cpumask_of(0);
 146         clockevents_config_and_register(&kona_clockevent_timer,
 147                 arch_timer_rate, 6, 0xffffffff);
 148 }
 149
 150 static irqreturn_t kona_timer_interrupt(int irq, void *dev_id)
 151 {
 152         struct clock_event_device *evt = &kona_clockevent_timer;
 153
 154         kona_timer_disable_and_clear(timers.tmr_regs);
 155         evt->event_handler(evt);
 156         return IRQ_HANDLED;
 157 }
 158
 159 static struct irqaction kona_timer_irq = {
 160         .name = "Kona Timer Tick",
 161         .flags = IRQF_TIMER,
 162         .handler = kona_timer_interrupt,
 163 };
 164
 165 static int __init kona_timer_init(struct device_node *node)
 166 {
 167         u32 freq;
 168         struct clk *external_clk;
 169
 170         external_clk = of_clk_get_by_name(node, NULL);
 171
 172         if (!IS_ERR(external_clk)) {
 173                 arch_timer_rate = clk_get_rate(external_clk);
 174                 clk_prepare_enable(external_clk);
 175         } else if (!of_property_read_u32(node, "clock-frequency", &freq)) {
 176                 arch_timer_rate = freq;
 177         } else {
 178                 pr_err("Kona Timer v1 unable to determine clock-frequency");
 179                 return -EINVAL;
 180         }
 181
 182         /* Setup IRQ numbers */
 183         timers.tmr_irq = irq_of_parse_and_map(node, 0);
 184
 185         /* Setup IO addresses */
 186         timers.tmr_regs = of_iomap(node, 0);
 187
 188         kona_timer_disable_and_clear(timers.tmr_regs);
 189
 190         kona_timer_clockevents_init();
 191         setup_irq(timers.tmr_irq, &kona_timer_irq);
 192         kona_timer_set_next_event((arch_timer_rate / HZ), NULL);
 193
 194         return 0;
 195 }
 196
 197 CLOCKSOURCE_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  */
 202 CLOCKSOURCE_OF_DECLARE(bcm_kona, "bcm,kona-timer", kona_timer_init);