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/err.h>
  19 #include <linux/io.h>
  20 #include <linux/sched.h>
  21
  22 #include <asm/sched_clock.h>
  23
  24 #include <plat/common.h>
  25 #include <plat/board.h>
  26
  27 #include <plat/clock.h>
  28
  29
  30 /*
  31  * 32KHz clocksource ... always available, on pretty most chips except
  32  * OMAP 730 and 1510.  Other timers could be used as clocksources, with
  33  * higher resolution in free-running counter modes (e.g. 12 MHz xtal),
  34  * but systems won't necessarily want to spend resources that way.
  35  */
  36
  37 #define OMAP16XX_TIMER_32K_SYNCHRONIZED         0xfffbc410
  38
  39 #include <linux/clocksource.h>
  40
  41 /*
  42  * offset_32k holds the init time counter value. It is then subtracted
  43  * from every counter read to achieve a counter that counts time from the
  44  * kernel boot (needed for sched_clock()).
  45  */
  46 static u32 offset_32k __read_mostly;
  47
  48 #ifdef CONFIG_ARCH_OMAP16XX
  49 static cycle_t notrace omap16xx_32k_read(struct clocksource *cs)
  50 {
  51         return omap_readl(OMAP16XX_TIMER_32K_SYNCHRONIZED) - offset_32k;
  52 }
  53 #else
  54 #define omap16xx_32k_read       NULL
  55 #endif
  56
  57 #ifdef CONFIG_ARCH_OMAP2420
  58 static cycle_t notrace omap2420_32k_read(struct clocksource *cs)
  59 {
  60         return omap_readl(OMAP2420_32KSYNCT_BASE + 0x10) - offset_32k;
  61 }
  62 #else
  63 #define omap2420_32k_read       NULL
  64 #endif
  65
  66 #ifdef CONFIG_ARCH_OMAP2430
  67 static cycle_t notrace omap2430_32k_read(struct clocksource *cs)
  68 {
  69         return omap_readl(OMAP2430_32KSYNCT_BASE + 0x10) - offset_32k;
  70 }
  71 #else
  72 #define omap2430_32k_read       NULL
  73 #endif
  74
  75 #ifdef CONFIG_ARCH_OMAP3
  76 static cycle_t notrace omap34xx_32k_read(struct clocksource *cs)
  77 {
  78         return omap_readl(OMAP3430_32KSYNCT_BASE + 0x10) - offset_32k;
  79 }
  80 #else
  81 #define omap34xx_32k_read       NULL
  82 #endif
  83
  84 #ifdef CONFIG_ARCH_OMAP4
  85 static cycle_t notrace omap44xx_32k_read(struct clocksource *cs)
  86 {
  87         return omap_readl(OMAP4430_32KSYNCT_BASE + 0x10) - offset_32k;
  88 }
  89 #else
  90 #define omap44xx_32k_read       NULL
  91 #endif
  92
  93 /*
  94  * Kernel assumes that sched_clock can be called early but may not have
  95  * things ready yet.
  96  */
  97 static cycle_t notrace omap_32k_read_dummy(struct clocksource *cs)
  98 {
  99         return 0;
 100 }
 101
 102 static struct clocksource clocksource_32k = {
 103         .name           = "32k_counter",
 104         .rating         = 250,
 105         .read           = omap_32k_read_dummy,
 106         .mask           = CLOCKSOURCE_MASK(32),
 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 static DEFINE_CLOCK_DATA(cd);
 115
 116 /*
 117  * Constants generated by clocks_calc_mult_shift(m, s, 32768, NSEC_PER_SEC, 60).
 118  * This gives a resolution of about 30us and a wrap period of about 36hrs.
 119  */
 120 #define SC_MULT         4000000000u
 121 #define SC_SHIFT        17
 122
 123 unsigned long long notrace sched_clock(void)
 124 {
 125         u32 cyc = clocksource_32k.read(&clocksource_32k);
 126         return cyc_to_fixed_sched_clock(&cd, cyc, (u32)~0, SC_MULT, SC_SHIFT);
 127 }
 128
 129 static void notrace omap_update_sched_clock(void)
 130 {
 131         u32 cyc = clocksource_32k.read(&clocksource_32k);
 132         update_sched_clock(&cd, cyc, (u32)~0);
 133 }
 134
 135 /**
 136  * read_persistent_clock -  Return time from a persistent clock.
 137  *
 138  * Reads the time from a source which isn't disabled during PM, the
 139  * 32k sync timer.  Convert the cycles elapsed since last read into
 140  * nsecs and adds to a monotonically increasing timespec.
 141  */
 142 static struct timespec persistent_ts;
 143 static cycles_t cycles, last_cycles;
 144 void read_persistent_clock(struct timespec *ts)
 145 {
 146         unsigned long long nsecs;
 147         cycles_t delta;
 148         struct timespec *tsp = &persistent_ts;
 149
 150         last_cycles = cycles;
 151         cycles = clocksource_32k.read(&clocksource_32k);
 152         delta = cycles - last_cycles;
 153
 154         nsecs = clocksource_cyc2ns(delta,
 155                                    clocksource_32k.mult, clocksource_32k.shift);
 156
 157         timespec_add_ns(tsp, nsecs);
 158         *ts = *tsp;
 159 }
 160
 161 int __init omap_init_clocksource_32k(void)
 162 {
 163         static char err[] __initdata = KERN_ERR
 164                         "%s: can't register clocksource!\n";
 165
 166         if (cpu_is_omap16xx() || cpu_class_is_omap2()) {
 167                 struct clk *sync_32k_ick;
 168
 169                 if (cpu_is_omap16xx())
 170                         clocksource_32k.read = omap16xx_32k_read;
 171                 else if (cpu_is_omap2420())
 172                         clocksource_32k.read = omap2420_32k_read;
 173                 else if (cpu_is_omap2430())
 174                         clocksource_32k.read = omap2430_32k_read;
 175                 else if (cpu_is_omap34xx())
 176                         clocksource_32k.read = omap34xx_32k_read;
 177                 else if (cpu_is_omap44xx())
 178                         clocksource_32k.read = omap44xx_32k_read;
 179                 else
 180                         return -ENODEV;
 181
 182                 sync_32k_ick = clk_get(NULL, "omap_32ksync_ick");
 183                 if (!IS_ERR(sync_32k_ick))
 184                         clk_enable(sync_32k_ick);
 185
 186                 offset_32k = clocksource_32k.read(&clocksource_32k);
 187
 188                 if (clocksource_register_hz(&clocksource_32k, 32768))
 189                         printk(err, clocksource_32k.name);
 190
 191                 init_fixed_sched_clock(&cd, omap_update_sched_clock, 32,
 192                                        32768, SC_MULT, SC_SHIFT);
 193         }
 194         return 0;
 195 }