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Release 4.14 drivers/clocksource/scx200_hrt.c

/*
 * 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); }

Contributors

PersonTokensPropCommitsCommitProp
Jim Cromie1773.91%133.33%
Magnus Damm417.39%133.33%
Thomas Gleixner28.70%133.33%
Total23100.00%3100.00%

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; /* Make sure scx200 has initialized the configuration block */ if (!scx200_cb_present()) return -ENODEV; /* Reserve the timer's ISA io-region for ourselves */ if (!request_region(scx200_cb_base + SCx200_TIMER_OFFSET, SCx200_TIMER_SIZE, "NatSemi SCx200 High-Resolution Timer")) { pr_warn("unable to lock timer region\n"); return -ENODEV; } /* write timer config */ outb(HR_TMEN | (mhz27 ? HR_TMCLKSEL : 0), scx200_cb_base + SCx200_TMCNFG_OFFSET); freq = (HRT_FREQ + ppm); if (mhz27) freq *= 27; pr_info("enabling scx200 high-res timer (%s MHz +%d ppm)\n", mhz27 ? "27":"1", ppm); return clocksource_register_hz(&cs_hrt, freq); }

Contributors

PersonTokensPropCommitsCommitProp
Jim Cromie7773.33%360.00%
Ingo Molnar1716.19%120.00%
John Stultz1110.48%120.00%
Total105100.00%5100.00%

module_init(init_hrt_clocksource); MODULE_AUTHOR("Jim Cromie <jim.cromie@gmail.com>"); MODULE_DESCRIPTION("clocksource on SCx200 HiRes Timer"); MODULE_LICENSE("GPL");

Overall Contributors

PersonTokensPropCommitsCommitProp
Jim Cromie22080.59%337.50%
Ingo Molnar3412.45%112.50%
John Stultz114.03%112.50%
Magnus Damm41.47%112.50%
Thomas Gleixner41.47%225.00%
Total273100.00%8100.00%
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