linux-imx

/*

 * Copyright (C) 2006 Jim Cromie

 *

 * This is a clocksource driver for the Geode SCx200's 1 or 27 MHz

 * high-resolution timer.  The Geode SC-1100 (at least) has a buggy

 * time stamp counter (TSC), which loses time unless 'idle=poll' is

 * given as a boot-arg. In its absence, the Generic Timekeeping code

 * will detect and de-rate the bad TSC, allowing this timer to take

 * over timekeeping duties.

 *

 * Based on work by John Stultz, and Ted Phelps (in a 2.6.12-rc6 patch)

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of the GNU General Public License as

 * published by the Free Software Foundation; either version 2 of the

 * License, or (at your option) any later version.

 */

​

#include <linux/clocksource.h>

#include <linux/init.h>

#include <linux/module.h>

#include <linux/ioport.h>

#include <linux/scx200.h>

​

#define NAME "scx200_hrt"

​

static int mhz27;

module_param(mhz27, int, 0);    /* load time only */

MODULE_PARM_DESC(mhz27, "count at 27.0 MHz (default is 1.0 MHz)");

​

static int ppm;

module_param(ppm, int, 0);  /* load time only */

MODULE_PARM_DESC(ppm, "+-adjust to actual XO freq (ppm)");

​

/* HiRes Timer configuration register address */

#define SCx200_TMCNFG_OFFSET (SCx200_TIMER_OFFSET + 5)

​

/* and config settings */

#define HR_TMEN (1 << 0)    /* timer interrupt enable */

#define HR_TMCLKSEL (1 << 1)    /* 1|0 counts at 27|1 MHz */

#define HR_TM27MPD (1 << 2) /* 1 turns off input clock (power-down) */

​

/* The base timer frequency, * 27 if selected */

#define HRT_FREQ   1000000

​

static u64 read_hrt(struct clocksource *cs)

{

    /* Read the timer value */

    return (u64) inl(scx200_cb_base + SCx200_TIMER_OFFSET);

}

​

static struct clocksource cs_hrt = {

    .name       = "scx200_hrt",

    .rating     = 250,

    .read       = read_hrt,

    .mask       = CLOCKSOURCE_MASK(32),

    .flags      = CLOCK_SOURCE_IS_CONTINUOUS,

    /* mult, shift are set based on mhz27 flag */

};

​

static int __init init_hrt_clocksource(void)

{

    u32 freq;