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Linux/arch/mips/ralink/cevt-rt3352.c

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  1 /*
  2  * This file is subject to the terms and conditions of the GNU General Public
  3  * License.  See the file "COPYING" in the main directory of this archive
  4  * for more details.
  5  *
  6  * Copyright (C) 2013 by John Crispin <john@phrozen.org>
  7  */
  8 
  9 #include <linux/clockchips.h>
 10 #include <linux/clocksource.h>
 11 #include <linux/interrupt.h>
 12 #include <linux/reset.h>
 13 #include <linux/init.h>
 14 #include <linux/time.h>
 15 #include <linux/of.h>
 16 #include <linux/of_irq.h>
 17 #include <linux/of_address.h>
 18 
 19 #include <asm/mach-ralink/ralink_regs.h>
 20 
 21 #define SYSTICK_FREQ            (50 * 1000)
 22 
 23 #define SYSTICK_CONFIG          0x00
 24 #define SYSTICK_COMPARE         0x04
 25 #define SYSTICK_COUNT           0x08
 26 
 27 /* route systick irq to mips irq 7 instead of the r4k-timer */
 28 #define CFG_EXT_STK_EN          0x2
 29 /* enable the counter */
 30 #define CFG_CNT_EN              0x1
 31 
 32 struct systick_device {
 33         void __iomem *membase;
 34         struct clock_event_device dev;
 35         int irq_requested;
 36         int freq_scale;
 37 };
 38 
 39 static int systick_set_oneshot(struct clock_event_device *evt);
 40 static int systick_shutdown(struct clock_event_device *evt);
 41 
 42 static int systick_next_event(unsigned long delta,
 43                                 struct clock_event_device *evt)
 44 {
 45         struct systick_device *sdev;
 46         u32 count;
 47 
 48         sdev = container_of(evt, struct systick_device, dev);
 49         count = ioread32(sdev->membase + SYSTICK_COUNT);
 50         count = (count + delta) % SYSTICK_FREQ;
 51         iowrite32(count, sdev->membase + SYSTICK_COMPARE);
 52 
 53         return 0;
 54 }
 55 
 56 static void systick_event_handler(struct clock_event_device *dev)
 57 {
 58         /* noting to do here */
 59 }
 60 
 61 static irqreturn_t systick_interrupt(int irq, void *dev_id)
 62 {
 63         struct clock_event_device *dev = (struct clock_event_device *) dev_id;
 64 
 65         dev->event_handler(dev);
 66 
 67         return IRQ_HANDLED;
 68 }
 69 
 70 static struct systick_device systick = {
 71         .dev = {
 72                 /*
 73                  * cevt-r4k uses 300, make sure systick
 74                  * gets used if available
 75                  */
 76                 .rating                 = 310,
 77                 .features               = CLOCK_EVT_FEAT_ONESHOT,
 78                 .set_next_event         = systick_next_event,
 79                 .set_state_shutdown     = systick_shutdown,
 80                 .set_state_oneshot      = systick_set_oneshot,
 81                 .event_handler          = systick_event_handler,
 82         },
 83 };
 84 
 85 static int systick_shutdown(struct clock_event_device *evt)
 86 {
 87         struct systick_device *sdev;
 88 
 89         sdev = container_of(evt, struct systick_device, dev);
 90 
 91         if (sdev->irq_requested)
 92                 free_irq(systick.dev.irq, &systick.dev);
 93         sdev->irq_requested = 0;
 94         iowrite32(0, systick.membase + SYSTICK_CONFIG);
 95 
 96         return 0;
 97 }
 98 
 99 static int systick_set_oneshot(struct clock_event_device *evt)
100 {
101         const char *name = systick.dev.name;
102         struct systick_device *sdev;
103         int irq = systick.dev.irq;
104 
105         sdev = container_of(evt, struct systick_device, dev);
106 
107         if (!sdev->irq_requested) {
108                 if (request_irq(irq, systick_interrupt,
109                                 IRQF_PERCPU | IRQF_TIMER, name, &systick.dev))
110                         pr_err("Failed to request irq %d (%s)\n", irq, name);
111         }
112         sdev->irq_requested = 1;
113         iowrite32(CFG_EXT_STK_EN | CFG_CNT_EN,
114                   systick.membase + SYSTICK_CONFIG);
115 
116         return 0;
117 }
118 
119 static int __init ralink_systick_init(struct device_node *np)
120 {
121         int ret;
122 
123         systick.membase = of_iomap(np, 0);
124         if (!systick.membase)
125                 return -ENXIO;
126 
127         systick.dev.name = np->name;
128         clockevents_calc_mult_shift(&systick.dev, SYSTICK_FREQ, 60);
129         systick.dev.max_delta_ns = clockevent_delta2ns(0x7fff, &systick.dev);
130         systick.dev.max_delta_ticks = 0x7fff;
131         systick.dev.min_delta_ns = clockevent_delta2ns(0x3, &systick.dev);
132         systick.dev.min_delta_ticks = 0x3;
133         systick.dev.irq = irq_of_parse_and_map(np, 0);
134         if (!systick.dev.irq) {
135                 pr_err("%pOFn: request_irq failed", np);
136                 return -EINVAL;
137         }
138 
139         ret = clocksource_mmio_init(systick.membase + SYSTICK_COUNT, np->name,
140                                     SYSTICK_FREQ, 301, 16,
141                                     clocksource_mmio_readl_up);
142         if (ret)
143                 return ret;
144 
145         clockevents_register_device(&systick.dev);
146 
147         pr_info("%pOFn: running - mult: %d, shift: %d\n",
148                         np, systick.dev.mult, systick.dev.shift);
149 
150         return 0;
151 }
152 
153 TIMER_OF_DECLARE(systick, "ralink,cevt-systick", ralink_systick_init);
154 

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