// SPDX-License-Identifier: GPL-2.0-or-later
|
/*
|
* 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)
|
*/
|
|
#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;
|
/* 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);
|
}
|
|
module_init(init_hrt_clocksource);
|
|
MODULE_AUTHOR("Jim Cromie <jim.cromie@gmail.com>");
|
MODULE_DESCRIPTION("clocksource on SCx200 HiRes Timer");
|
MODULE_LICENSE("GPL");
|
