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 *timer_base, uint32_t *msw, uint32_t *lsw)
  72 {
  73         void __iomem *base = IOMEM(timer_base);
  74         int loop_limit = 4;
  75
  76         /*
  77          * Read 64-bit free running counter
  78          * 1. Read hi-word
  79          * 2. Read low-word
  80          * 3. Read hi-word again
  81          * 4.1
  82          *      if new hi-word is not equal to previously read hi-word, then
  83          *      start from #1
  84          * 4.2
  85          *      if new hi-word is equal to previously read hi-word then stop.
  86          */
  87
  88         while (--loop_limit) {
  89                 *msw = readl(base + KONA_GPTIMER_STCHI_OFFSET);
  90                 *lsw = readl(base + KONA_GPTIMER_STCLO_OFFSET);
  91                 if (*msw == readl(base + KONA_GPTIMER_STCHI_OFFSET))
  92                         break;
  93         }
  94         if (!loop_limit) {
  95                 pr_err("bcm_kona_timer: getting counter failed.\n");
  96                 pr_err(" Timer will be impacted\n");
  97         }
  98
  99         return;
 100 }
 101
 102 static int kona_timer_set_next_event(unsigned long clc,
 103                                   struct clock_event_device *unused)
 104 {
 105         /*
 106          * timer (0) is disabled by the timer interrupt already
 107          * so, here we reload the next event value and re-enable
 108          * the timer.
 109          *
 110          * This way, we are potentially losing the time between
 111          * timer-interrupt->set_next_event. CPU local timers, when
 112          * they come in should get rid of skew.
 113          */
 114
 115         uint32_t lsw, msw;
 116         uint32_t reg;
 117
 118         kona_timer_get_counter(timers.tmr_regs, &msw, &lsw);
 119
 120         /* Load the "next" event tick value */
 121         writel(lsw + clc, timers.tmr_regs + KONA_GPTIMER_STCM0_OFFSET);
 122
 123         /* Enable compare */
 124         reg = readl(timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
 125         reg |= (1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
 126         writel(reg, timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
 127
 128         return 0;
 129 }
 130
 131 static void kona_timer_set_mode(enum clock_event_mode mode,
 132                              struct clock_event_device *unused)
 133 {
 134         switch (mode) {
 135         case CLOCK_EVT_MODE_ONESHOT:
 136                 /* by default mode is one shot don't do any thing */
 137                 break;
 138         case CLOCK_EVT_MODE_UNUSED:
 139         case CLOCK_EVT_MODE_SHUTDOWN:
 140         default:
 141                 kona_timer_disable_and_clear(timers.tmr_regs);
 142         }
 143 }
 144
 145 static struct clock_event_device kona_clockevent_timer = {
 146         .name = "timer 1",
 147         .features = CLOCK_EVT_FEAT_ONESHOT,
 148         .set_next_event = kona_timer_set_next_event,
 149         .set_mode = kona_timer_set_mode
 150 };
 151
 152 static void __init kona_timer_clockevents_init(void)
 153 {
 154         kona_clockevent_timer.cpumask = cpumask_of(0);
 155         clockevents_config_and_register(&kona_clockevent_timer,
 156                 arch_timer_rate, 6, 0xffffffff);
 157 }
 158
 159 static irqreturn_t kona_timer_interrupt(int irq, void *dev_id)
 160 {
 161         struct clock_event_device *evt = &kona_clockevent_timer;
 162
 163         kona_timer_disable_and_clear(timers.tmr_regs);
 164         evt->event_handler(evt);
 165         return IRQ_HANDLED;
 166 }
 167
 168 static struct irqaction kona_timer_irq = {
 169         .name = "Kona Timer Tick",
 170         .flags = IRQF_TIMER,
 171         .handler = kona_timer_interrupt,
 172 };
 173
 174 static void __init kona_timer_init(struct device_node *node)
 175 {
 176         u32 freq;
 177         struct clk *external_clk;
 178
 179         if (!of_device_is_available(node)) {
 180                 pr_info("Kona Timer v1 marked as disabled in device tree\n");
 181                 return;
 182         }
 183
 184         external_clk = of_clk_get_by_name(node, NULL);
 185
 186         if (!IS_ERR(external_clk)) {
 187                 arch_timer_rate = clk_get_rate(external_clk);
 188                 clk_prepare_enable(external_clk);
 189         } else if (!of_property_read_u32(node, "clock-frequency", &freq)) {
 190                 arch_timer_rate = freq;
 191         } else {
 192                 pr_err("Kona Timer v1 unable to determine clock-frequency");
 193                 return;
 194         }
 195
 196         /* Setup IRQ numbers */
 197         timers.tmr_irq = irq_of_parse_and_map(node, 0);
 198
 199         /* Setup IO addresses */
 200         timers.tmr_regs = of_iomap(node, 0);
 201
 202         kona_timer_disable_and_clear(timers.tmr_regs);
 203
 204         kona_timer_clockevents_init();
 205         setup_irq(timers.tmr_irq, &kona_timer_irq);
 206         kona_timer_set_next_event((arch_timer_rate / HZ), NULL);
 207 }
 208
 209 CLOCKSOURCE_OF_DECLARE(brcm_kona, "brcm,kona-timer", kona_timer_init);
 210 /*
 211  * bcm,kona-timer is deprecated by brcm,kona-timer
 212  * being kept here for driver compatibility
 213  */
 214 CLOCKSOURCE_OF_DECLARE(bcm_kona, "bcm,kona-timer", kona_timer_init);