arch/arm/plat-omap/counter_32k.c

   1 /*
   2  * OMAP 32ksynctimer/counter_32k-related code
   3  *
   4  * Copyright (C) 2009 Texas Instruments
   5  * Copyright (C) 2010 Nokia Corporation
   6  * Tony Lindgren <tony@atomide.com>
   7  * Added OMAP4 support - Santosh Shilimkar <santosh.shilimkar@ti.com>
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12  *
  13  * NOTE: This timer is not the same timer as the old OMAP1 MPU timer.
  14  */
  15 #include <linux/kernel.h>
  16 #include <linux/init.h>
  17 #include <linux/clk.h>
  18 #include <linux/io.h>
  19 #include <linux/err.h>
  20
  21 #include <plat/common.h>
  22 #include <plat/board.h>
  23
  24 #include <plat/clock.h>
  25
  26
  27 /*
  28  * 32KHz clocksource ... always available, on pretty most chips except
  29  * OMAP 730 and 1510.  Other timers could be used as clocksources, with
  30  * higher resolution in free-running counter modes (e.g. 12 MHz xtal),
  31  * but systems won't necessarily want to spend resources that way.
  32  */
  33
  34 #define OMAP16XX_TIMER_32K_SYNCHRONIZED         0xfffbc410
  35
  36 #if !(defined(CONFIG_ARCH_OMAP730) || defined(CONFIG_ARCH_OMAP15XX))
  37
  38 #include <linux/clocksource.h>
  39
  40 /*
  41  * offset_32k holds the init time counter value. It is then subtracted
  42  * from every counter read to achieve a counter that counts time from the
  43  * kernel boot (needed for sched_clock()).
  44  */
  45 static u32 offset_32k __read_mostly;
  46
  47 #ifdef CONFIG_ARCH_OMAP16XX
  48 static cycle_t omap16xx_32k_read(struct clocksource *cs)
  49 {
  50         return omap_readl(OMAP16XX_TIMER_32K_SYNCHRONIZED) - offset_32k;
  51 }
  52 #else
  53 #define omap16xx_32k_read       NULL
  54 #endif
  55
  56 #ifdef CONFIG_ARCH_OMAP2420
  57 static cycle_t omap2420_32k_read(struct clocksource *cs)
  58 {
  59         return omap_readl(OMAP2420_32KSYNCT_BASE + 0x10) - offset_32k;
  60 }
  61 #else
  62 #define omap2420_32k_read       NULL
  63 #endif
  64
  65 #ifdef CONFIG_ARCH_OMAP2430
  66 static cycle_t omap2430_32k_read(struct clocksource *cs)
  67 {
  68         return omap_readl(OMAP2430_32KSYNCT_BASE + 0x10) - offset_32k;
  69 }
  70 #else
  71 #define omap2430_32k_read       NULL
  72 #endif
  73
  74 #ifdef CONFIG_ARCH_OMAP3
  75 static cycle_t omap34xx_32k_read(struct clocksource *cs)
  76 {
  77         return omap_readl(OMAP3430_32KSYNCT_BASE + 0x10) - offset_32k;
  78 }
  79 #else
  80 #define omap34xx_32k_read       NULL
  81 #endif
  82
  83 #ifdef CONFIG_ARCH_OMAP4
  84 static cycle_t omap44xx_32k_read(struct clocksource *cs)
  85 {
  86         return omap_readl(OMAP4430_32KSYNCT_BASE + 0x10) - offset_32k;
  87 }
  88 #else
  89 #define omap44xx_32k_read       NULL
  90 #endif
  91
  92 /*
  93  * Kernel assumes that sched_clock can be called early but may not have
  94  * things ready yet.
  95  */
  96 static cycle_t omap_32k_read_dummy(struct clocksource *cs)
  97 {
  98         return 0;
  99 }
 100
 101 static struct clocksource clocksource_32k = {
 102         .name           = "32k_counter",
 103         .rating         = 250,
 104         .read           = omap_32k_read_dummy,
 105         .mask           = CLOCKSOURCE_MASK(32),
 106         .shift          = 10,
 107         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
 108 };
 109
 110 /*
 111  * Returns current time from boot in nsecs. It's OK for this to wrap
 112  * around for now, as it's just a relative time stamp.
 113  */
 114 unsigned long long sched_clock(void)
 115 {
 116         return clocksource_cyc2ns(clocksource_32k.read(&clocksource_32k),
 117                                   clocksource_32k.mult, clocksource_32k.shift);
 118 }
 119
 120 /**
 121  * read_persistent_clock -  Return time from a persistent clock.
 122  *
 123  * Reads the time from a source which isn't disabled during PM, the
 124  * 32k sync timer.  Convert the cycles elapsed since last read into
 125  * nsecs and adds to a monotonically increasing timespec.
 126  */
 127 static struct timespec persistent_ts;
 128 static cycles_t cycles, last_cycles;
 129 void read_persistent_clock(struct timespec *ts)
 130 {
 131         unsigned long long nsecs;
 132         cycles_t delta;
 133         struct timespec *tsp = &persistent_ts;
 134
 135         last_cycles = cycles;
 136         cycles = clocksource_32k.read(&clocksource_32k);
 137         delta = cycles - last_cycles;
 138
 139         nsecs = clocksource_cyc2ns(delta,
 140                                    clocksource_32k.mult, clocksource_32k.shift);
 141
 142         timespec_add_ns(tsp, nsecs);
 143         *ts = *tsp;
 144 }
 145
 146 static int __init omap_init_clocksource_32k(void)
 147 {
 148         static char err[] __initdata = KERN_ERR
 149                         "%s: can't register clocksource!\n";
 150
 151         if (cpu_is_omap16xx() || cpu_class_is_omap2()) {
 152                 struct clk *sync_32k_ick;
 153
 154                 if (cpu_is_omap16xx())
 155                         clocksource_32k.read = omap16xx_32k_read;
 156                 else if (cpu_is_omap2420())
 157                         clocksource_32k.read = omap2420_32k_read;
 158                 else if (cpu_is_omap2430())
 159                         clocksource_32k.read = omap2430_32k_read;
 160                 else if (cpu_is_omap34xx())
 161                         clocksource_32k.read = omap34xx_32k_read;
 162                 else if (cpu_is_omap44xx())
 163                         clocksource_32k.read = omap44xx_32k_read;
 164                 else
 165                         return -ENODEV;
 166
 167                 sync_32k_ick = clk_get(NULL, "omap_32ksync_ick");
 168                 if (!IS_ERR(sync_32k_ick))
 169                         clk_enable(sync_32k_ick);
 170
 171                 clocksource_32k.mult = clocksource_hz2mult(32768,
 172                                             clocksource_32k.shift);
 173
 174                 offset_32k = clocksource_32k.read(&clocksource_32k);
 175
 176                 if (clocksource_register(&clocksource_32k))
 177                         printk(err, clocksource_32k.name);
 178         }
 179         return 0;
 180 }
 181 arch_initcall(omap_init_clocksource_32k);
 182
 183 #endif  /* !(defined(CONFIG_ARCH_OMAP730) || defined(CONFIG_ARCH_OMAP15XX)) */
 184