arch/mips/ralink/cevt-rt3352.c

   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);