drivers/clocksource/vt8500_timer.c

   1 /*
   2  *  arch/arm/mach-vt8500/timer.c
   3  *
   4  *  Copyright (C) 2012 Tony Prisk <linux@prisktech.co.nz>
   5  *  Copyright (C) 2010 Alexey Charkov <alchark@gmail.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20  */
  21
  22 /*
  23  * This file is copied and modified from the original timer.c provided by
  24  * Alexey Charkov. Minor changes have been made for Device Tree Support.
  25  */
  26
  27 #include <linux/io.h>
  28 #include <linux/irq.h>
  29 #include <linux/interrupt.h>
  30 #include <linux/clocksource.h>
  31 #include <linux/clockchips.h>
  32 #include <linux/delay.h>
  33
  34 #include <linux/of.h>
  35 #include <linux/of_address.h>
  36 #include <linux/of_irq.h>
  37
  38 #define VT8500_TIMER_OFFSET     0x0100
  39 #define VT8500_TIMER_HZ         3000000
  40 #define TIMER_MATCH_VAL         0x0000
  41 #define TIMER_COUNT_VAL         0x0010
  42 #define TIMER_STATUS_VAL        0x0014
  43 #define TIMER_IER_VAL           0x001c          /* interrupt enable */
  44 #define TIMER_CTRL_VAL          0x0020
  45 #define TIMER_AS_VAL            0x0024          /* access status */
  46 #define TIMER_COUNT_R_ACTIVE    (1 << 5)        /* not ready for read */
  47 #define TIMER_COUNT_W_ACTIVE    (1 << 4)        /* not ready for write */
  48 #define TIMER_MATCH_W_ACTIVE    (1 << 0)        /* not ready for write */
  49
  50 #define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)
  51
  52 #define MIN_OSCR_DELTA          16
  53
  54 static void __iomem *regbase;
  55
  56 static u64 vt8500_timer_read(struct clocksource *cs)
  57 {
  58         int loops = msecs_to_loops(10);
  59         writel(3, regbase + TIMER_CTRL_VAL);
  60         while ((readl((regbase + TIMER_AS_VAL)) & TIMER_COUNT_R_ACTIVE)
  61                                                 && --loops)
  62                 cpu_relax();
  63         return readl(regbase + TIMER_COUNT_VAL);
  64 }
  65
  66 static struct clocksource clocksource = {
  67         .name           = "vt8500_timer",
  68         .rating         = 200,
  69         .read           = vt8500_timer_read,
  70         .mask           = CLOCKSOURCE_MASK(32),
  71         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  72 };
  73
  74 static int vt8500_timer_set_next_event(unsigned long cycles,
  75                                     struct clock_event_device *evt)
  76 {
  77         int loops = msecs_to_loops(10);
  78         u64 alarm = clocksource.read(&clocksource) + cycles;
  79         while ((readl(regbase + TIMER_AS_VAL) & TIMER_MATCH_W_ACTIVE)
  80                                                 && --loops)
  81                 cpu_relax();
  82         writel((unsigned long)alarm, regbase + TIMER_MATCH_VAL);
  83
  84         if ((signed)(alarm - clocksource.read(&clocksource)) <= MIN_OSCR_DELTA)
  85                 return -ETIME;
  86
  87         writel(1, regbase + TIMER_IER_VAL);
  88
  89         return 0;
  90 }
  91
  92 static int vt8500_shutdown(struct clock_event_device *evt)
  93 {
  94         writel(readl(regbase + TIMER_CTRL_VAL) | 1, regbase + TIMER_CTRL_VAL);
  95         writel(0, regbase + TIMER_IER_VAL);
  96         return 0;
  97 }
  98
  99 static struct clock_event_device clockevent = {
 100         .name                   = "vt8500_timer",
 101         .features               = CLOCK_EVT_FEAT_ONESHOT,
 102         .rating                 = 200,
 103         .set_next_event         = vt8500_timer_set_next_event,
 104         .set_state_shutdown     = vt8500_shutdown,
 105         .set_state_oneshot      = vt8500_shutdown,
 106 };
 107
 108 static irqreturn_t vt8500_timer_interrupt(int irq, void *dev_id)
 109 {
 110         struct clock_event_device *evt = dev_id;
 111         writel(0xf, regbase + TIMER_STATUS_VAL);
 112         evt->event_handler(evt);
 113
 114         return IRQ_HANDLED;
 115 }
 116
 117 static struct irqaction irq = {
 118         .name    = "vt8500_timer",
 119         .flags   = IRQF_TIMER | IRQF_IRQPOLL,
 120         .handler = vt8500_timer_interrupt,
 121         .dev_id  = &clockevent,
 122 };
 123
 124 static int __init vt8500_timer_init(struct device_node *np)
 125 {
 126         int timer_irq, ret;
 127
 128         regbase = of_iomap(np, 0);
 129         if (!regbase) {
 130                 pr_err("%s: Missing iobase description in Device Tree\n",
 131                                                                 __func__);
 132                 return -ENXIO;
 133         }
 134
 135         timer_irq = irq_of_parse_and_map(np, 0);
 136         if (!timer_irq) {
 137                 pr_err("%s: Missing irq description in Device Tree\n",
 138                                                                 __func__);
 139                 return -EINVAL;
 140         }
 141
 142         writel(1, regbase + TIMER_CTRL_VAL);
 143         writel(0xf, regbase + TIMER_STATUS_VAL);
 144         writel(~0, regbase + TIMER_MATCH_VAL);
 145
 146         ret = clocksource_register_hz(&clocksource, VT8500_TIMER_HZ);
 147         if (ret) {
 148                 pr_err("%s: vt8500_timer_init: clocksource_register failed for %s\n",
 149                        __func__, clocksource.name);
 150                 return ret;
 151         }
 152
 153         clockevent.cpumask = cpumask_of(0);
 154
 155         ret = setup_irq(timer_irq, &irq);
 156         if (ret) {
 157                 pr_err("%s: setup_irq failed for %s\n", __func__,
 158                                                         clockevent.name);
 159                 return ret;
 160         }
 161
 162         clockevents_config_and_register(&clockevent, VT8500_TIMER_HZ,
 163                                         MIN_OSCR_DELTA * 2, 0xf0000000);
 164
 165         return 0;
 166 }
 167
 168 TIMER_OF_DECLARE(vt8500, "via,vt8500-timer", vt8500_timer_init);