mmio.c

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/*
 * Generic MMIO clocksource support
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/clocksource.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>

struct clocksource_mmio {
    void __iomem *reg;
    struct clocksource clksrc;
};

static inline struct clocksource_mmio *to_mmio_clksrc(struct clocksource *c)
{
    return container_of(c, struct clocksource_mmio, clksrc);
}

cycle_t clocksource_mmio_readl_up(struct clocksource *c)
{
    return readl_relaxed(to_mmio_clksrc(c)->reg);
}

cycle_t clocksource_mmio_readl_down(struct clocksource *c)
{
    return ~readl_relaxed(to_mmio_clksrc(c)->reg);
}

cycle_t clocksource_mmio_readw_up(struct clocksource *c)
{
    return readw_relaxed(to_mmio_clksrc(c)->reg);
}

cycle_t clocksource_mmio_readw_down(struct clocksource *c)
{
    return ~(unsigned)readw_relaxed(to_mmio_clksrc(c)->reg);
}

int __init clocksource_mmio_init(void __iomem *base, const char *name,
    unsigned long hz, int rating, unsigned bits,
    cycle_t (*read)(struct clocksource *))
{
    struct clocksource_mmio *cs;

    if (bits > 32 || bits < 16)
        return -EINVAL;

    cs = kzalloc(sizeof(struct clocksource_mmio), GFP_KERNEL);
    if (!cs)
        return -ENOMEM;

    cs->reg = base;
    cs->clksrc.name = name;
    cs->clksrc.rating = rating;
    cs->clksrc.read = read;
    cs->clksrc.mask = CLOCKSOURCE_MASK(bits);
    cs->clksrc.flags = CLOCK_SOURCE_IS_CONTINUOUS;

    return clocksource_register_hz(&cs->clksrc, hz);
}