arch/arm/mach-imx/epit.c

   1 /*
   2  *  linux/arch/arm/plat-mxc/epit.c
   3  *
   4  *  Copyright (C) 2010 Sascha Hauer <s.hauer@pengutronix.de>
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version 2
   9  * of the License, or (at your option) any later version.
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
  18  * MA 02110-1301, USA.
  19  */
  20
  21 #define EPITCR          0x00
  22 #define EPITSR          0x04
  23 #define EPITLR          0x08
  24 #define EPITCMPR        0x0c
  25 #define EPITCNR         0x10
  26
  27 #define EPITCR_EN                       (1 << 0)
  28 #define EPITCR_ENMOD                    (1 << 1)
  29 #define EPITCR_OCIEN                    (1 << 2)
  30 #define EPITCR_RLD                      (1 << 3)
  31 #define EPITCR_PRESC(x)                 (((x) & 0xfff) << 4)
  32 #define EPITCR_SWR                      (1 << 16)
  33 #define EPITCR_IOVW                     (1 << 17)
  34 #define EPITCR_DBGEN                    (1 << 18)
  35 #define EPITCR_WAITEN                   (1 << 19)
  36 #define EPITCR_RES                      (1 << 20)
  37 #define EPITCR_STOPEN                   (1 << 21)
  38 #define EPITCR_OM_DISCON                (0 << 22)
  39 #define EPITCR_OM_TOGGLE                (1 << 22)
  40 #define EPITCR_OM_CLEAR                 (2 << 22)
  41 #define EPITCR_OM_SET                   (3 << 22)
  42 #define EPITCR_CLKSRC_OFF               (0 << 24)
  43 #define EPITCR_CLKSRC_PERIPHERAL        (1 << 24)
  44 #define EPITCR_CLKSRC_REF_HIGH          (1 << 24)
  45 #define EPITCR_CLKSRC_REF_LOW           (3 << 24)
  46
  47 #define EPITSR_OCIF                     (1 << 0)
  48
  49 #include <linux/interrupt.h>
  50 #include <linux/irq.h>
  51 #include <linux/clockchips.h>
  52 #include <linux/clk.h>
  53 #include <linux/err.h>
  54 #include <asm/mach/time.h>
  55
  56 #include "common.h"
  57 #include "hardware.h"
  58
  59 static struct clock_event_device clockevent_epit;
  60
  61 static void __iomem *timer_base;
  62
  63 static inline void epit_irq_disable(void)
  64 {
  65         u32 val;
  66
  67         val = imx_readl(timer_base + EPITCR);
  68         val &= ~EPITCR_OCIEN;
  69         imx_writel(val, timer_base + EPITCR);
  70 }
  71
  72 static inline void epit_irq_enable(void)
  73 {
  74         u32 val;
  75
  76         val = imx_readl(timer_base + EPITCR);
  77         val |= EPITCR_OCIEN;
  78         imx_writel(val, timer_base + EPITCR);
  79 }
  80
  81 static void epit_irq_acknowledge(void)
  82 {
  83         imx_writel(EPITSR_OCIF, timer_base + EPITSR);
  84 }
  85
  86 static int __init epit_clocksource_init(struct clk *timer_clk)
  87 {
  88         unsigned int c = clk_get_rate(timer_clk);
  89
  90         return clocksource_mmio_init(timer_base + EPITCNR, "epit", c, 200, 32,
  91                         clocksource_mmio_readl_down);
  92 }
  93
  94 /* clock event */
  95
  96 static int epit_set_next_event(unsigned long evt,
  97                               struct clock_event_device *unused)
  98 {
  99         unsigned long tcmp;
 100
 101         tcmp = imx_readl(timer_base + EPITCNR);
 102
 103         imx_writel(tcmp - evt, timer_base + EPITCMPR);
 104
 105         return 0;
 106 }
 107
 108 /* Left event sources disabled, no more interrupts appear */
 109 static int epit_shutdown(struct clock_event_device *evt)
 110 {
 111         unsigned long flags;
 112
 113         /*
 114          * The timer interrupt generation is disabled at least
 115          * for enough time to call epit_set_next_event()
 116          */
 117         local_irq_save(flags);
 118
 119         /* Disable interrupt in GPT module */
 120         epit_irq_disable();
 121
 122         /* Clear pending interrupt */
 123         epit_irq_acknowledge();
 124
 125         local_irq_restore(flags);
 126
 127         return 0;
 128 }
 129
 130 static int epit_set_oneshot(struct clock_event_device *evt)
 131 {
 132         unsigned long flags;
 133
 134         /*
 135          * The timer interrupt generation is disabled at least
 136          * for enough time to call epit_set_next_event()
 137          */
 138         local_irq_save(flags);
 139
 140         /* Disable interrupt in GPT module */
 141         epit_irq_disable();
 142
 143         /* Clear pending interrupt, only while switching mode */
 144         if (!clockevent_state_oneshot(evt))
 145                 epit_irq_acknowledge();
 146
 147         /*
 148          * Do not put overhead of interrupt enable/disable into
 149          * epit_set_next_event(), the core has about 4 minutes
 150          * to call epit_set_next_event() or shutdown clock after
 151          * mode switching
 152          */
 153         epit_irq_enable();
 154         local_irq_restore(flags);
 155
 156         return 0;
 157 }
 158
 159 /*
 160  * IRQ handler for the timer
 161  */
 162 static irqreturn_t epit_timer_interrupt(int irq, void *dev_id)
 163 {
 164         struct clock_event_device *evt = &clockevent_epit;
 165
 166         epit_irq_acknowledge();
 167
 168         evt->event_handler(evt);
 169
 170         return IRQ_HANDLED;
 171 }
 172
 173 static struct irqaction epit_timer_irq = {
 174         .name           = "i.MX EPIT Timer Tick",
 175         .flags          = IRQF_TIMER | IRQF_IRQPOLL,
 176         .handler        = epit_timer_interrupt,
 177 };
 178
 179 static struct clock_event_device clockevent_epit = {
 180         .name                   = "epit",
 181         .features               = CLOCK_EVT_FEAT_ONESHOT,
 182         .set_state_shutdown     = epit_shutdown,
 183         .tick_resume            = epit_shutdown,
 184         .set_state_oneshot      = epit_set_oneshot,
 185         .set_next_event         = epit_set_next_event,
 186         .rating                 = 200,
 187 };
 188
 189 static int __init epit_clockevent_init(struct clk *timer_clk)
 190 {
 191         clockevent_epit.cpumask = cpumask_of(0);
 192         clockevents_config_and_register(&clockevent_epit,
 193                                         clk_get_rate(timer_clk),
 194                                         0x800, 0xfffffffe);
 195
 196         return 0;
 197 }
 198
 199 void __init epit_timer_init(void __iomem *base, int irq)
 200 {
 201         struct clk *timer_clk;
 202
 203         timer_clk = clk_get_sys("imx-epit.0", NULL);
 204         if (IS_ERR(timer_clk)) {
 205                 pr_err("i.MX epit: unable to get clk\n");
 206                 return;
 207         }
 208
 209         clk_prepare_enable(timer_clk);
 210
 211         timer_base = base;
 212
 213         /*
 214          * Initialise to a known state (all timers off, and timing reset)
 215          */
 216         imx_writel(0x0, timer_base + EPITCR);
 217
 218         imx_writel(0xffffffff, timer_base + EPITLR);
 219         imx_writel(EPITCR_EN | EPITCR_CLKSRC_REF_HIGH | EPITCR_WAITEN,
 220                    timer_base + EPITCR);
 221
 222         /* init and register the timer to the framework */
 223         epit_clocksource_init(timer_clk);
 224         epit_clockevent_init(timer_clk);
 225
 226         /* Make irqs happen */
 227         setup_irq(irq, &epit_timer_irq);
 228 }