arch/arm/mach-spear/time.c

   1 /*
   2  * arch/arm/plat-spear/time.c
   3  *
   4  * Copyright (C) 2010 ST Microelectronics
   5  * Shiraz Hashim<shiraz.linux.kernel@gmail.com>
   6  *
   7  * This file is licensed under the terms of the GNU General Public
   8  * License version 2. This program is licensed "as is" without any
   9  * warranty of any kind, whether express or implied.
  10  */
  11
  12 #include <linux/clk.h>
  13 #include <linux/clockchips.h>
  14 #include <linux/clocksource.h>
  15 #include <linux/err.h>
  16 #include <linux/init.h>
  17 #include <linux/interrupt.h>
  18 #include <linux/ioport.h>
  19 #include <linux/io.h>
  20 #include <linux/kernel.h>
  21 #include <linux/of_irq.h>
  22 #include <linux/of_address.h>
  23 #include <linux/time.h>
  24 #include <linux/irq.h>
  25 #include <asm/mach/time.h>
  26 #include "generic.h"
  27
  28 /*
  29  * We would use TIMER0 and TIMER1 as clockevent and clocksource.
  30  * Timer0 and Timer1 both belong to same gpt block in cpu subbsystem. Further
  31  * they share same functional clock. Any change in one's functional clock will
  32  * also affect other timer.
  33  */
  34
  35 #define CLKEVT  0       /* gpt0, channel0 as clockevent */
  36 #define CLKSRC  1       /* gpt0, channel1 as clocksource */
  37
  38 /* Register offsets, x is channel number */
  39 #define CR(x)           ((x) * 0x80 + 0x80)
  40 #define IR(x)           ((x) * 0x80 + 0x84)
  41 #define LOAD(x)         ((x) * 0x80 + 0x88)
  42 #define COUNT(x)        ((x) * 0x80 + 0x8C)
  43
  44 /* Reg bit definitions */
  45 #define CTRL_INT_ENABLE         0x0100
  46 #define CTRL_ENABLE             0x0020
  47 #define CTRL_ONE_SHOT           0x0010
  48
  49 #define CTRL_PRESCALER1         0x0
  50 #define CTRL_PRESCALER2         0x1
  51 #define CTRL_PRESCALER4         0x2
  52 #define CTRL_PRESCALER8         0x3
  53 #define CTRL_PRESCALER16        0x4
  54 #define CTRL_PRESCALER32        0x5
  55 #define CTRL_PRESCALER64        0x6
  56 #define CTRL_PRESCALER128       0x7
  57 #define CTRL_PRESCALER256       0x8
  58
  59 #define INT_STATUS              0x1
  60
  61 /*
  62  * Minimum clocksource/clockevent timer range in seconds
  63  */
  64 #define SPEAR_MIN_RANGE 4
  65
  66 static __iomem void *gpt_base;
  67 static struct clk *gpt_clk;
  68
  69 static int clockevent_next_event(unsigned long evt,
  70                                  struct clock_event_device *clk_event_dev);
  71
  72 static void __init spear_clocksource_init(void)
  73 {
  74         u32 tick_rate;
  75         u16 val;
  76
  77         /* program the prescaler (/256)*/
  78         writew(CTRL_PRESCALER256, gpt_base + CR(CLKSRC));
  79
  80         /* find out actual clock driving Timer */
  81         tick_rate = clk_get_rate(gpt_clk);
  82         tick_rate >>= CTRL_PRESCALER256;
  83
  84         writew(0xFFFF, gpt_base + LOAD(CLKSRC));
  85
  86         val = readw(gpt_base + CR(CLKSRC));
  87         val &= ~CTRL_ONE_SHOT;  /* autoreload mode */
  88         val |= CTRL_ENABLE ;
  89         writew(val, gpt_base + CR(CLKSRC));
  90
  91         /* register the clocksource */
  92         clocksource_mmio_init(gpt_base + COUNT(CLKSRC), "tmr1", tick_rate,
  93                 200, 16, clocksource_mmio_readw_up);
  94 }
  95
  96 static inline void timer_shutdown(struct clock_event_device *evt)
  97 {
  98         u16 val = readw(gpt_base + CR(CLKEVT));
  99
 100         /* stop the timer */
 101         val &= ~CTRL_ENABLE;
 102         writew(val, gpt_base + CR(CLKEVT));
 103 }
 104
 105 static int spear_shutdown(struct clock_event_device *evt)
 106 {
 107         timer_shutdown(evt);
 108
 109         return 0;
 110 }
 111
 112 static int spear_set_oneshot(struct clock_event_device *evt)
 113 {
 114         u16 val;
 115
 116         /* stop the timer */
 117         timer_shutdown(evt);
 118
 119         val = readw(gpt_base + CR(CLKEVT));
 120         val |= CTRL_ONE_SHOT;
 121         writew(val, gpt_base + CR(CLKEVT));
 122
 123         return 0;
 124 }
 125
 126 static int spear_set_periodic(struct clock_event_device *evt)
 127 {
 128         u32 period;
 129         u16 val;
 130
 131         /* stop the timer */
 132         timer_shutdown(evt);
 133
 134         period = clk_get_rate(gpt_clk) / HZ;
 135         period >>= CTRL_PRESCALER16;
 136         writew(period, gpt_base + LOAD(CLKEVT));
 137
 138         val = readw(gpt_base + CR(CLKEVT));
 139         val &= ~CTRL_ONE_SHOT;
 140         val |= CTRL_ENABLE | CTRL_INT_ENABLE;
 141         writew(val, gpt_base + CR(CLKEVT));
 142
 143         return 0;
 144 }
 145
 146 static struct clock_event_device clkevt = {
 147         .name = "tmr0",
 148         .features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
 149         .set_state_shutdown = spear_shutdown,
 150         .set_state_periodic = spear_set_periodic,
 151         .set_state_oneshot = spear_set_oneshot,
 152         .tick_resume = spear_shutdown,
 153         .set_next_event = clockevent_next_event,
 154         .shift = 0,     /* to be computed */
 155 };
 156
 157 static int clockevent_next_event(unsigned long cycles,
 158                                  struct clock_event_device *clk_event_dev)
 159 {
 160         u16 val = readw(gpt_base + CR(CLKEVT));
 161
 162         if (val & CTRL_ENABLE)
 163                 writew(val & ~CTRL_ENABLE, gpt_base + CR(CLKEVT));
 164
 165         writew(cycles, gpt_base + LOAD(CLKEVT));
 166
 167         val |= CTRL_ENABLE | CTRL_INT_ENABLE;
 168         writew(val, gpt_base + CR(CLKEVT));
 169
 170         return 0;
 171 }
 172
 173 static irqreturn_t spear_timer_interrupt(int irq, void *dev_id)
 174 {
 175         struct clock_event_device *evt = &clkevt;
 176
 177         writew(INT_STATUS, gpt_base + IR(CLKEVT));
 178
 179         evt->event_handler(evt);
 180
 181         return IRQ_HANDLED;
 182 }
 183
 184 static struct irqaction spear_timer_irq = {
 185         .name = "timer",
 186         .flags = IRQF_TIMER,
 187         .handler = spear_timer_interrupt
 188 };
 189
 190 static void __init spear_clockevent_init(int irq)
 191 {
 192         u32 tick_rate;
 193
 194         /* program the prescaler */
 195         writew(CTRL_PRESCALER16, gpt_base + CR(CLKEVT));
 196
 197         tick_rate = clk_get_rate(gpt_clk);
 198         tick_rate >>= CTRL_PRESCALER16;
 199
 200         clkevt.cpumask = cpumask_of(0);
 201
 202         clockevents_config_and_register(&clkevt, tick_rate, 3, 0xfff0);
 203
 204         setup_irq(irq, &spear_timer_irq);
 205 }
 206
 207 static const struct of_device_id timer_of_match[] __initconst = {
 208         { .compatible = "st,spear-timer", },
 209         { },
 210 };
 211
 212 void __init spear_setup_of_timer(void)
 213 {
 214         struct device_node *np;
 215         int irq, ret;
 216
 217         np = of_find_matching_node(NULL, timer_of_match);
 218         if (!np) {
 219                 pr_err("%s: No timer passed via DT\n", __func__);
 220                 return;
 221         }
 222
 223         irq = irq_of_parse_and_map(np, 0);
 224         if (!irq) {
 225                 pr_err("%s: No irq passed for timer via DT\n", __func__);
 226                 return;
 227         }
 228
 229         gpt_base = of_iomap(np, 0);
 230         if (!gpt_base) {
 231                 pr_err("%s: of iomap failed\n", __func__);
 232                 return;
 233         }
 234
 235         gpt_clk = clk_get_sys("gpt0", NULL);
 236         if (!gpt_clk) {
 237                 pr_err("%s:couldn't get clk for gpt\n", __func__);
 238                 goto err_iomap;
 239         }
 240
 241         ret = clk_prepare_enable(gpt_clk);
 242         if (ret < 0) {
 243                 pr_err("%s:couldn't prepare-enable gpt clock\n", __func__);
 244                 goto err_prepare_enable_clk;
 245         }
 246
 247         spear_clockevent_init(irq);
 248         spear_clocksource_init();
 249
 250         return;
 251
 252 err_prepare_enable_clk:
 253         clk_put(gpt_clk);
 254 err_iomap:
 255         iounmap(gpt_base);
 256 }