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 #include <asm/mach/time.h>
  24
  25 #include <linux/of.h>
  26 #include <linux/of_address.h>
  27 #include <linux/of_irq.h>
  28
  29
  30 #define KONA_GPTIMER_STCS_OFFSET                        0x00000000
  31 #define KONA_GPTIMER_STCLO_OFFSET                       0x00000004
  32 #define KONA_GPTIMER_STCHI_OFFSET                       0x00000008
  33 #define KONA_GPTIMER_STCM0_OFFSET                       0x0000000C
  34
  35 #define KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT             0
  36 #define KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT          4
  37
  38 struct kona_bcm_timers {
  39         int tmr_irq;
  40         void __iomem *tmr_regs;
  41 };
  42
  43 static struct kona_bcm_timers timers;
  44
  45 static u32 arch_timer_rate;
  46
  47 /*
  48  * We use the peripheral timers for system tick, the cpu global timer for
  49  * profile tick
  50  */
  51 static void kona_timer_disable_and_clear(void __iomem *base)
  52 {
  53         uint32_t reg;
  54
  55         /*
  56          * clear and disable interrupts
  57          * We are using compare/match register 0 for our system interrupts
  58          */
  59         reg = readl(base + KONA_GPTIMER_STCS_OFFSET);
  60
  61         /* Clear compare (0) interrupt */
  62         reg |= 1 << KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT;
  63         /* disable compare */
  64         reg &= ~(1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
  65
  66         writel(reg, base + KONA_GPTIMER_STCS_OFFSET);
  67
  68 }
  69
  70 static void
  71 kona_timer_get_counter(void __iomem *timer_base, uint32_t *msw, uint32_t *lsw)
  72 {
  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(timer_base + KONA_GPTIMER_STCHI_OFFSET);
  89                 *lsw = readl(timer_base + KONA_GPTIMER_STCLO_OFFSET);
  90                 if (*msw == readl(timer_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 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
 117         kona_timer_get_counter(timers.tmr_regs, &msw, &lsw);
 118
 119         /* Load the "next" event tick value */
 120         writel(lsw + clc, timers.tmr_regs + KONA_GPTIMER_STCM0_OFFSET);
 121
 122         /* Enable compare */
 123         reg = readl(timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
 124         reg |= (1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
 125         writel(reg, timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
 126
 127         return 0;
 128 }
 129
 130 static int kona_timer_shutdown(struct clock_event_device *evt)
 131 {
 132         kona_timer_disable_and_clear(timers.tmr_regs);
 133         return 0;
 134 }
 135
 136 static struct clock_event_device kona_clockevent_timer = {
 137         .name = "timer 1",
 138         .features = CLOCK_EVT_FEAT_ONESHOT,
 139         .set_next_event = kona_timer_set_next_event,
 140         .set_state_shutdown = kona_timer_shutdown,
 141         .tick_resume = kona_timer_shutdown,
 142 };
 143
 144 static void __init kona_timer_clockevents_init(void)
 145 {
 146         kona_clockevent_timer.cpumask = cpumask_of(0);
 147         clockevents_config_and_register(&kona_clockevent_timer,
 148                 arch_timer_rate, 6, 0xffffffff);
 149 }
 150
 151 static irqreturn_t kona_timer_interrupt(int irq, void *dev_id)
 152 {
 153         struct clock_event_device *evt = &kona_clockevent_timer;
 154
 155         kona_timer_disable_and_clear(timers.tmr_regs);
 156         evt->event_handler(evt);
 157         return IRQ_HANDLED;
 158 }
 159
 160 static struct irqaction kona_timer_irq = {
 161         .name = "Kona Timer Tick",
 162         .flags = IRQF_TIMER,
 163         .handler = kona_timer_interrupt,
 164 };
 165
 166 static void __init kona_timer_init(struct device_node *node)
 167 {
 168         u32 freq;
 169         struct clk *external_clk;
 170
 171         if (!of_device_is_available(node)) {
 172                 pr_info("Kona Timer v1 marked as disabled in device tree\n");
 173                 return;
 174         }
 175
 176         external_clk = of_clk_get_by_name(node, NULL);
 177
 178         if (!IS_ERR(external_clk)) {
 179                 arch_timer_rate = clk_get_rate(external_clk);
 180                 clk_prepare_enable(external_clk);
 181         } else if (!of_property_read_u32(node, "clock-frequency", &freq)) {
 182                 arch_timer_rate = freq;
 183         } else {
 184                 pr_err("Kona Timer v1 unable to determine clock-frequency");
 185                 return;
 186         }
 187
 188         /* Setup IRQ numbers */
 189         timers.tmr_irq = irq_of_parse_and_map(node, 0);
 190
 191         /* Setup IO addresses */
 192         timers.tmr_regs = of_iomap(node, 0);
 193
 194         kona_timer_disable_and_clear(timers.tmr_regs);
 195
 196         kona_timer_clockevents_init();
 197         setup_irq(timers.tmr_irq, &kona_timer_irq);
 198         kona_timer_set_next_event((arch_timer_rate / HZ), NULL);
 199 }
 200
 201 CLOCKSOURCE_OF_DECLARE(brcm_kona, "brcm,kona-timer", kona_timer_init);
 202 /*
 203  * bcm,kona-timer is deprecated by brcm,kona-timer
 204  * being kept here for driver compatibility
 205  */
 206 CLOCKSOURCE_OF_DECLARE(bcm_kona, "bcm,kona-timer", kona_timer_init);