linux/drivers/clocksource/clksrc-dbx500-prcmu.c
<<
>>
Prefs
   1/*
   2 * Copyright (C) ST-Ericsson SA 2011
   3 *
   4 * License Terms: GNU General Public License v2
   5 * Author: Mattias Wallin <mattias.wallin@stericsson.com> for ST-Ericsson
   6 * Author: Sundar Iyer for ST-Ericsson
   7 * sched_clock implementation is based on:
   8 * plat-nomadik/timer.c Linus Walleij <linus.walleij@stericsson.com>
   9 *
  10 * DBx500-PRCMU Timer
  11 * The PRCMU has 5 timers which are available in a always-on
  12 * power domain.  We use the Timer 4 for our always-on clock
  13 * source on DB8500.
  14 */
  15#include <linux/clockchips.h>
  16#include <linux/clksrc-dbx500-prcmu.h>
  17#include <linux/sched_clock.h>
  18
  19#define RATE_32K                32768
  20
  21#define TIMER_MODE_CONTINOUS    0x1
  22#define TIMER_DOWNCOUNT_VAL     0xffffffff
  23
  24#define PRCMU_TIMER_REF         0
  25#define PRCMU_TIMER_DOWNCOUNT   0x4
  26#define PRCMU_TIMER_MODE        0x8
  27
  28#define SCHED_CLOCK_MIN_WRAP 131072 /* 2^32 / 32768 */
  29
  30static void __iomem *clksrc_dbx500_timer_base;
  31
  32static cycle_t notrace clksrc_dbx500_prcmu_read(struct clocksource *cs)
  33{
  34        void __iomem *base = clksrc_dbx500_timer_base;
  35        u32 count, count2;
  36
  37        do {
  38                count = readl_relaxed(base + PRCMU_TIMER_DOWNCOUNT);
  39                count2 = readl_relaxed(base + PRCMU_TIMER_DOWNCOUNT);
  40        } while (count2 != count);
  41
  42        /* Negate because the timer is a decrementing counter */
  43        return ~count;
  44}
  45
  46static struct clocksource clocksource_dbx500_prcmu = {
  47        .name           = "dbx500-prcmu-timer",
  48        .rating         = 300,
  49        .read           = clksrc_dbx500_prcmu_read,
  50        .mask           = CLOCKSOURCE_MASK(32),
  51        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  52};
  53
  54#ifdef CONFIG_CLKSRC_DBX500_PRCMU_SCHED_CLOCK
  55
  56static u32 notrace dbx500_prcmu_sched_clock_read(void)
  57{
  58        if (unlikely(!clksrc_dbx500_timer_base))
  59                return 0;
  60
  61        return clksrc_dbx500_prcmu_read(&clocksource_dbx500_prcmu);
  62}
  63
  64#endif
  65
  66void __init clksrc_dbx500_prcmu_init(void __iomem *base)
  67{
  68        clksrc_dbx500_timer_base = base;
  69
  70        /*
  71         * The A9 sub system expects the timer to be configured as
  72         * a continous looping timer.
  73         * The PRCMU should configure it but if it for some reason
  74         * don't we do it here.
  75         */
  76        if (readl(clksrc_dbx500_timer_base + PRCMU_TIMER_MODE) !=
  77            TIMER_MODE_CONTINOUS) {
  78                writel(TIMER_MODE_CONTINOUS,
  79                       clksrc_dbx500_timer_base + PRCMU_TIMER_MODE);
  80                writel(TIMER_DOWNCOUNT_VAL,
  81                       clksrc_dbx500_timer_base + PRCMU_TIMER_REF);
  82        }
  83#ifdef CONFIG_CLKSRC_DBX500_PRCMU_SCHED_CLOCK
  84        setup_sched_clock(dbx500_prcmu_sched_clock_read,
  85                         32, RATE_32K);
  86#endif
  87        clocksource_register_hz(&clocksource_dbx500_prcmu, RATE_32K);
  88}
  89
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.