linux/drivers/clocksource/mmio.c
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   1/*
   2 * Generic MMIO clocksource support
   3 *
   4 * This program is free software; you can redistribute it and/or modify
   5 * it under the terms of the GNU General Public License version 2 as
   6 * published by the Free Software Foundation.
   7 */
   8#include <linux/clocksource.h>
   9#include <linux/errno.h>
  10#include <linux/init.h>
  11#include <linux/slab.h>
  12
  13struct clocksource_mmio {
  14        void __iomem *reg;
  15        struct clocksource clksrc;
  16};
  17
  18static inline struct clocksource_mmio *to_mmio_clksrc(struct clocksource *c)
  19{
  20        return container_of(c, struct clocksource_mmio, clksrc);
  21}
  22
  23cycle_t clocksource_mmio_readl_up(struct clocksource *c)
  24{
  25        return readl_relaxed(to_mmio_clksrc(c)->reg);
  26}
  27
  28cycle_t clocksource_mmio_readl_down(struct clocksource *c)
  29{
  30        return ~readl_relaxed(to_mmio_clksrc(c)->reg);
  31}
  32
  33cycle_t clocksource_mmio_readw_up(struct clocksource *c)
  34{
  35        return readw_relaxed(to_mmio_clksrc(c)->reg);
  36}
  37
  38cycle_t clocksource_mmio_readw_down(struct clocksource *c)
  39{
  40        return ~(unsigned)readw_relaxed(to_mmio_clksrc(c)->reg);
  41}
  42
  43/**
  44 * clocksource_mmio_init - Initialize a simple mmio based clocksource
  45 * @base:       Virtual address of the clock readout register
  46 * @name:       Name of the clocksource
  47 * @hz:         Frequency of the clocksource in Hz
  48 * @rating:     Rating of the clocksource
  49 * @bits:       Number of valid bits
  50 * @read:       One of clocksource_mmio_read*() above
  51 */
  52int __init clocksource_mmio_init(void __iomem *base, const char *name,
  53        unsigned long hz, int rating, unsigned bits,
  54        cycle_t (*read)(struct clocksource *))
  55{
  56        struct clocksource_mmio *cs;
  57
  58        if (bits > 32 || bits < 16)
  59                return -EINVAL;
  60
  61        cs = kzalloc(sizeof(struct clocksource_mmio), GFP_KERNEL);
  62        if (!cs)
  63                return -ENOMEM;
  64
  65        cs->reg = base;
  66        cs->clksrc.name = name;
  67        cs->clksrc.rating = rating;
  68        cs->clksrc.read = read;
  69        cs->clksrc.mask = CLOCKSOURCE_MASK(bits);
  70        cs->clksrc.flags = CLOCK_SOURCE_IS_CONTINUOUS;
  71
  72        return clocksource_register_hz(&cs->clksrc, hz);
  73}
  74
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