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/clocksource.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  * 32KHz clocksource ... always available, on pretty most chips except
  31  * OMAP 730 and 1510.  Other timers could be used as clocksources, with
  32  * higher resolution in free-running counter modes (e.g. 12 MHz xtal),
  33  * but systems won't necessarily want to spend resources that way.
  34  */
  35 static void __iomem *timer_32k_base;
  36
  37 #define OMAP16XX_TIMER_32K_SYNCHRONIZED         0xfffbc410
  38
  39 static u32 notrace omap_32k_read_sched_clock(void)
  40 {
  41         return timer_32k_base ? __raw_readl(timer_32k_base) : 0;
  42 }
  43
  44 /**
  45  * read_persistent_clock -  Return time from a persistent clock.
  46  *
  47  * Reads the time from a source which isn't disabled during PM, the
  48  * 32k sync timer.  Convert the cycles elapsed since last read into
  49  * nsecs and adds to a monotonically increasing timespec.
  50  */
  51 static struct timespec persistent_ts;
  52 static cycles_t cycles, last_cycles;
  53 static unsigned int persistent_mult, persistent_shift;
  54 void read_persistent_clock(struct timespec *ts)
  55 {
  56         unsigned long long nsecs;
  57         cycles_t delta;
  58         struct timespec *tsp = &persistent_ts;
  59
  60         last_cycles = cycles;
  61         cycles = timer_32k_base ? __raw_readl(timer_32k_base) : 0;
  62         delta = cycles - last_cycles;
  63
  64         nsecs = clocksource_cyc2ns(delta, persistent_mult, persistent_shift);
  65
  66         timespec_add_ns(tsp, nsecs);
  67         *ts = *tsp;
  68 }
  69
  70 int __init omap_init_clocksource_32k(void)
  71 {
  72         static char err[] __initdata = KERN_ERR
  73                         "%s: can't register clocksource!\n";
  74
  75         if (cpu_is_omap16xx() || cpu_class_is_omap2()) {
  76                 u32 pbase;
  77                 unsigned long size = SZ_4K;
  78                 void __iomem *base;
  79                 struct clk *sync_32k_ick;
  80
  81                 if (cpu_is_omap16xx()) {
  82                         pbase = OMAP16XX_TIMER_32K_SYNCHRONIZED;
  83                         size = SZ_1K;
  84                 } else if (cpu_is_omap2420())
  85                         pbase = OMAP2420_32KSYNCT_BASE + 0x10;
  86                 else if (cpu_is_omap2430())
  87                         pbase = OMAP2430_32KSYNCT_BASE + 0x10;
  88                 else if (cpu_is_omap34xx())
  89                         pbase = OMAP3430_32KSYNCT_BASE + 0x10;
  90                 else if (cpu_is_omap44xx())
  91                         pbase = OMAP4430_32KSYNCT_BASE + 0x10;
  92                 else
  93                         return -ENODEV;
  94
  95                 /* For this to work we must have a static mapping in io.c for this area */
  96                 base = ioremap(pbase, size);
  97                 if (!base)
  98                         return -ENODEV;
  99
 100                 sync_32k_ick = clk_get(NULL, "omap_32ksync_ick");
 101                 if (!IS_ERR(sync_32k_ick))
 102                         clk_enable(sync_32k_ick);
 103
 104                 timer_32k_base = base;
 105
 106                 /*
 107                  * 120000 rough estimate from the calculations in
 108                  * __clocksource_updatefreq_scale.
 109                  */
 110                 clocks_calc_mult_shift(&persistent_mult, &persistent_shift,
 111                                 32768, NSEC_PER_SEC, 120000);
 112
 113                 if (clocksource_mmio_init(base, "32k_counter", 32768, 250, 32,
 114                                           clocksource_mmio_readl_up))
 115                         printk(err, "32k_counter");
 116
 117                 setup_sched_clock(omap_32k_read_sched_clock, 32, 32768);
 118         }
 119         return 0;
 120 }