2874c5fd28
Based on 1 normalized pattern(s): 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 extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 3029 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Allison Randal <allison@lohutok.net> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
90 lines
2.5 KiB
C
90 lines
2.5 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Copyright (C) 2006 Jim Cromie
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*
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* This is a clocksource driver for the Geode SCx200's 1 or 27 MHz
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* high-resolution timer. The Geode SC-1100 (at least) has a buggy
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* time stamp counter (TSC), which loses time unless 'idle=poll' is
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* given as a boot-arg. In its absence, the Generic Timekeeping code
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* will detect and de-rate the bad TSC, allowing this timer to take
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* over timekeeping duties.
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*
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* Based on work by John Stultz, and Ted Phelps (in a 2.6.12-rc6 patch)
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*/
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#include <linux/clocksource.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/ioport.h>
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#include <linux/scx200.h>
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#define NAME "scx200_hrt"
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static int mhz27;
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module_param(mhz27, int, 0); /* load time only */
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MODULE_PARM_DESC(mhz27, "count at 27.0 MHz (default is 1.0 MHz)");
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static int ppm;
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module_param(ppm, int, 0); /* load time only */
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MODULE_PARM_DESC(ppm, "+-adjust to actual XO freq (ppm)");
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/* HiRes Timer configuration register address */
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#define SCx200_TMCNFG_OFFSET (SCx200_TIMER_OFFSET + 5)
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/* and config settings */
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#define HR_TMEN (1 << 0) /* timer interrupt enable */
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#define HR_TMCLKSEL (1 << 1) /* 1|0 counts at 27|1 MHz */
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#define HR_TM27MPD (1 << 2) /* 1 turns off input clock (power-down) */
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/* The base timer frequency, * 27 if selected */
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#define HRT_FREQ 1000000
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static u64 read_hrt(struct clocksource *cs)
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{
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/* Read the timer value */
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return (u64) inl(scx200_cb_base + SCx200_TIMER_OFFSET);
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}
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static struct clocksource cs_hrt = {
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.name = "scx200_hrt",
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.rating = 250,
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.read = read_hrt,
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.mask = CLOCKSOURCE_MASK(32),
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.flags = CLOCK_SOURCE_IS_CONTINUOUS,
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/* mult, shift are set based on mhz27 flag */
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};
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static int __init init_hrt_clocksource(void)
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{
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u32 freq;
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/* Make sure scx200 has initialized the configuration block */
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if (!scx200_cb_present())
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return -ENODEV;
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/* Reserve the timer's ISA io-region for ourselves */
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if (!request_region(scx200_cb_base + SCx200_TIMER_OFFSET,
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SCx200_TIMER_SIZE,
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"NatSemi SCx200 High-Resolution Timer")) {
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pr_warn("unable to lock timer region\n");
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return -ENODEV;
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}
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/* write timer config */
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outb(HR_TMEN | (mhz27 ? HR_TMCLKSEL : 0),
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scx200_cb_base + SCx200_TMCNFG_OFFSET);
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freq = (HRT_FREQ + ppm);
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if (mhz27)
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freq *= 27;
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pr_info("enabling scx200 high-res timer (%s MHz +%d ppm)\n", mhz27 ? "27":"1", ppm);
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return clocksource_register_hz(&cs_hrt, freq);
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}
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module_init(init_hrt_clocksource);
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MODULE_AUTHOR("Jim Cromie <jim.cromie@gmail.com>");
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MODULE_DESCRIPTION("clocksource on SCx200 HiRes Timer");
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MODULE_LICENSE("GPL");
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