drivers/clocksource/timer-ralink.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Ralink System Tick Counter driver present on RT3352 and MT7620 SoCs.
   4  *
   5  * Copyright (C) 2013 by John Crispin <john@phrozen.org>
   6  */
   7
   8 #include <linux/clockchips.h>
   9 #include <linux/clocksource.h>
  10 #include <linux/interrupt.h>
  11 #include <linux/reset.h>
  12 #include <linux/init.h>
  13 #include <linux/time.h>
  14 #include <linux/of.h>
  15 #include <linux/of_irq.h>
  16 #include <linux/of_address.h>
  17
  18 #define SYSTICK_FREQ            (50 * 1000)
  19
  20 #define SYSTICK_CONFIG          0x00
  21 #define SYSTICK_COMPARE         0x04
  22 #define SYSTICK_COUNT           0x08
  23
  24 /* route systick irq to mips irq 7 instead of the r4k-timer */
  25 #define CFG_EXT_STK_EN          0x2
  26 /* enable the counter */
  27 #define CFG_CNT_EN              0x1
  28
  29 struct systick_device {
  30         void __iomem *membase;
  31         struct clock_event_device dev;
  32         int irq_requested;
  33         int freq_scale;
  34 };
  35
  36 static int systick_set_oneshot(struct clock_event_device *evt);
  37 static int systick_shutdown(struct clock_event_device *evt);
  38
  39 static int systick_next_event(unsigned long delta,
  40                               struct clock_event_device *evt)
  41 {
  42         struct systick_device *sdev;
  43         u32 count;
  44
  45         sdev = container_of(evt, struct systick_device, dev);
  46         count = ioread32(sdev->membase + SYSTICK_COUNT);
  47         count = (count + delta) % SYSTICK_FREQ;
  48         iowrite32(count, sdev->membase + SYSTICK_COMPARE);
  49
  50         return 0;
  51 }
  52
  53 static void systick_event_handler(struct clock_event_device *dev)
  54 {
  55         /* noting to do here */
  56 }
  57
  58 static irqreturn_t systick_interrupt(int irq, void *dev_id)
  59 {
  60         struct clock_event_device *dev = (struct clock_event_device *)dev_id;
  61
  62         dev->event_handler(dev);
  63
  64         return IRQ_HANDLED;
  65 }
  66
  67 static struct systick_device systick = {
  68         .dev = {
  69                 /*
  70                  * cevt-r4k uses 300, make sure systick
  71                  * gets used if available
  72                  */
  73                 .rating                 = 310,
  74                 .features               = CLOCK_EVT_FEAT_ONESHOT,
  75                 .set_next_event         = systick_next_event,
  76                 .set_state_shutdown     = systick_shutdown,
  77                 .set_state_oneshot      = systick_set_oneshot,
  78                 .event_handler          = systick_event_handler,
  79         },
  80 };
  81
  82 static int systick_shutdown(struct clock_event_device *evt)
  83 {
  84         struct systick_device *sdev;
  85
  86         sdev = container_of(evt, struct systick_device, dev);
  87
  88         if (sdev->irq_requested)
  89                 free_irq(systick.dev.irq, &systick.dev);
  90         sdev->irq_requested = 0;
  91         iowrite32(0, systick.membase + SYSTICK_CONFIG);
  92
  93         return 0;
  94 }
  95
  96 static int systick_set_oneshot(struct clock_event_device *evt)
  97 {
  98         const char *name = systick.dev.name;
  99         struct systick_device *sdev;
 100         int irq = systick.dev.irq;
 101
 102         sdev = container_of(evt, struct systick_device, dev);
 103
 104         if (!sdev->irq_requested) {
 105                 if (request_irq(irq, systick_interrupt,
 106                                 IRQF_PERCPU | IRQF_TIMER, name, &systick.dev))
 107                         pr_err("Failed to request irq %d (%s)\n", irq, name);
 108         }
 109         sdev->irq_requested = 1;
 110         iowrite32(CFG_EXT_STK_EN | CFG_CNT_EN,
 111                   systick.membase + SYSTICK_CONFIG);
 112
 113         return 0;
 114 }
 115
 116 static int __init ralink_systick_init(struct device_node *np)
 117 {
 118         int ret;
 119
 120         systick.membase = of_iomap(np, 0);
 121         if (!systick.membase)
 122                 return -ENXIO;
 123
 124         systick.dev.name = np->name;
 125         clockevents_calc_mult_shift(&systick.dev, SYSTICK_FREQ, 60);
 126         systick.dev.max_delta_ns = clockevent_delta2ns(0x7fff, &systick.dev);
 127         systick.dev.max_delta_ticks = 0x7fff;
 128         systick.dev.min_delta_ns = clockevent_delta2ns(0x3, &systick.dev);
 129         systick.dev.min_delta_ticks = 0x3;
 130         systick.dev.irq = irq_of_parse_and_map(np, 0);
 131         if (!systick.dev.irq) {
 132                 pr_err("%pOFn: request_irq failed", np);
 133                 return -EINVAL;
 134         }
 135
 136         ret = clocksource_mmio_init(systick.membase + SYSTICK_COUNT, np->name,
 137                                     SYSTICK_FREQ, 301, 16,
 138                                     clocksource_mmio_readl_up);
 139         if (ret)
 140                 return ret;
 141
 142         clockevents_register_device(&systick.dev);
 143
 144         pr_info("%pOFn: running - mult: %d, shift: %d\n",
 145                         np, systick.dev.mult, systick.dev.shift);
 146
 147         return 0;
 148 }
 149
 150 TIMER_OF_DECLARE(systick, "ralink,cevt-systick", ralink_systick_init);