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Linux/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 int
 70 kona_timer_get_counter(void __iomem *timer_base, uint32_t *msw, uint32_t *lsw)
 71 {
 72         int loop_limit = 3;
 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         do {
 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         } while (--loop_limit);
 92         if (!loop_limit) {
 93                 pr_err("bcm_kona_timer: getting counter failed.\n");
 94                 pr_err(" Timer will be impacted\n");
 95                 return -ETIMEDOUT;
 96         }
 97 
 98         return 0;
 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         int ret;
117 
118         ret = kona_timer_get_counter(timers.tmr_regs, &msw, &lsw);
119         if (ret)
120                 return ret;
121 
122         /* Load the "next" event tick value */
123         writel(lsw + clc, timers.tmr_regs + KONA_GPTIMER_STCM0_OFFSET);
124 
125         /* Enable compare */
126         reg = readl(timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
127         reg |= (1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
128         writel(reg, timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
129 
130         return 0;
131 }
132 
133 static int kona_timer_shutdown(struct clock_event_device *evt)
134 {
135         kona_timer_disable_and_clear(timers.tmr_regs);
136         return 0;
137 }
138 
139 static struct clock_event_device kona_clockevent_timer = {
140         .name = "timer 1",
141         .features = CLOCK_EVT_FEAT_ONESHOT,
142         .set_next_event = kona_timer_set_next_event,
143         .set_state_shutdown = kona_timer_shutdown,
144         .tick_resume = kona_timer_shutdown,
145 };
146 
147 static void __init kona_timer_clockevents_init(void)
148 {
149         kona_clockevent_timer.cpumask = cpumask_of(0);
150         clockevents_config_and_register(&kona_clockevent_timer,
151                 arch_timer_rate, 6, 0xffffffff);
152 }
153 
154 static irqreturn_t kona_timer_interrupt(int irq, void *dev_id)
155 {
156         struct clock_event_device *evt = &kona_clockevent_timer;
157 
158         kona_timer_disable_and_clear(timers.tmr_regs);
159         evt->event_handler(evt);
160         return IRQ_HANDLED;
161 }
162 
163 static struct irqaction kona_timer_irq = {
164         .name = "Kona Timer Tick",
165         .flags = IRQF_TIMER,
166         .handler = kona_timer_interrupt,
167 };
168 
169 static int __init kona_timer_init(struct device_node *node)
170 {
171         u32 freq;
172         struct clk *external_clk;
173 
174         external_clk = of_clk_get_by_name(node, NULL);
175 
176         if (!IS_ERR(external_clk)) {
177                 arch_timer_rate = clk_get_rate(external_clk);
178                 clk_prepare_enable(external_clk);
179         } else if (!of_property_read_u32(node, "clock-frequency", &freq)) {
180                 arch_timer_rate = freq;
181         } else {
182                 pr_err("Kona Timer v1 unable to determine clock-frequency");
183                 return -EINVAL;
184         }
185 
186         /* Setup IRQ numbers */
187         timers.tmr_irq = irq_of_parse_and_map(node, 0);
188 
189         /* Setup IO addresses */
190         timers.tmr_regs = of_iomap(node, 0);
191 
192         kona_timer_disable_and_clear(timers.tmr_regs);
193 
194         kona_timer_clockevents_init();
195         setup_irq(timers.tmr_irq, &kona_timer_irq);
196         kona_timer_set_next_event((arch_timer_rate / HZ), NULL);
197 
198         return 0;
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);
207 

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