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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 #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 void kona_timer_set_mode(enum clock_event_mode mode,
131                              struct clock_event_device *unused)
132 {
133         switch (mode) {
134         case CLOCK_EVT_MODE_ONESHOT:
135                 /* by default mode is one shot don't do any thing */
136                 break;
137         case CLOCK_EVT_MODE_UNUSED:
138         case CLOCK_EVT_MODE_SHUTDOWN:
139         default:
140                 kona_timer_disable_and_clear(timers.tmr_regs);
141         }
142 }
143 
144 static struct clock_event_device kona_clockevent_timer = {
145         .name = "timer 1",
146         .features = CLOCK_EVT_FEAT_ONESHOT,
147         .set_next_event = kona_timer_set_next_event,
148         .set_mode = kona_timer_set_mode
149 };
150 
151 static void __init kona_timer_clockevents_init(void)
152 {
153         kona_clockevent_timer.cpumask = cpumask_of(0);
154         clockevents_config_and_register(&kona_clockevent_timer,
155                 arch_timer_rate, 6, 0xffffffff);
156 }
157 
158 static irqreturn_t kona_timer_interrupt(int irq, void *dev_id)
159 {
160         struct clock_event_device *evt = &kona_clockevent_timer;
161 
162         kona_timer_disable_and_clear(timers.tmr_regs);
163         evt->event_handler(evt);
164         return IRQ_HANDLED;
165 }
166 
167 static struct irqaction kona_timer_irq = {
168         .name = "Kona Timer Tick",
169         .flags = IRQF_TIMER,
170         .handler = kona_timer_interrupt,
171 };
172 
173 static void __init kona_timer_init(struct device_node *node)
174 {
175         u32 freq;
176         struct clk *external_clk;
177 
178         if (!of_device_is_available(node)) {
179                 pr_info("Kona Timer v1 marked as disabled in device tree\n");
180                 return;
181         }
182 
183         external_clk = of_clk_get_by_name(node, NULL);
184 
185         if (!IS_ERR(external_clk)) {
186                 arch_timer_rate = clk_get_rate(external_clk);
187                 clk_prepare_enable(external_clk);
188         } else if (!of_property_read_u32(node, "clock-frequency", &freq)) {
189                 arch_timer_rate = freq;
190         } else {
191                 pr_err("Kona Timer v1 unable to determine clock-frequency");
192                 return;
193         }
194 
195         /* Setup IRQ numbers */
196         timers.tmr_irq = irq_of_parse_and_map(node, 0);
197 
198         /* Setup IO addresses */
199         timers.tmr_regs = of_iomap(node, 0);
200 
201         kona_timer_disable_and_clear(timers.tmr_regs);
202 
203         kona_timer_clockevents_init();
204         setup_irq(timers.tmr_irq, &kona_timer_irq);
205         kona_timer_set_next_event((arch_timer_rate / HZ), NULL);
206 }
207 
208 CLOCKSOURCE_OF_DECLARE(brcm_kona, "brcm,kona-timer", kona_timer_init);
209 /*
210  * bcm,kona-timer is deprecated by brcm,kona-timer
211  * being kept here for driver compatibility
212  */
213 CLOCKSOURCE_OF_DECLARE(bcm_kona, "bcm,kona-timer", kona_timer_init);
214 

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