From 6ae7440e6b7a46f4c119c60580aa9384c1b463f7 Mon Sep 17 00:00:00 2001 From: Jim Cromie Date: Mon, 26 Jun 2006 00:25:19 -0700 Subject: [PATCH] GTOD: add scx200 HRT clocksource Add a GTOD clocksource driver based on the Geode SCx200's Hi-Res Timer. Signed-off-by: Jim Cromie Cc: Roman Zippel Cc: john stultz Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/clocksource/Makefile | 5 +- drivers/clocksource/scx200_hrt.c | 101 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 104 insertions(+), 2 deletions(-) create mode 100644 drivers/clocksource/scx200_hrt.c (limited to 'drivers/clocksource') diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile index be3511a308c..a5222547022 100644 --- a/drivers/clocksource/Makefile +++ b/drivers/clocksource/Makefile @@ -1,2 +1,3 @@ -obj-$(CONFIG_X86_CYCLONE_TIMER) += cyclone.o -obj-$(CONFIG_X86_PM_TIMER) += acpi_pm.o +obj-$(CONFIG_X86_CYCLONE_TIMER) += cyclone.o +obj-$(CONFIG_X86_PM_TIMER) += acpi_pm.o +obj-$(CONFIG_SCx200HR_TIMER) += scx200_hrt.o diff --git a/drivers/clocksource/scx200_hrt.c b/drivers/clocksource/scx200_hrt.c new file mode 100644 index 00000000000..d418b829721 --- /dev/null +++ b/drivers/clocksource/scx200_hrt.c @@ -0,0 +1,101 @@ +/* + * 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 +#include +#include +#include +#include + +#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 cycle_t read_hrt(void) +{ + /* Read the timer value */ + return (cycle_t) inl(scx200_cb_base + SCx200_TIMER_OFFSET); +} + +#define HRT_SHIFT_1 22 +#define HRT_SHIFT_27 26 + +static struct clocksource cs_hrt = { + .name = "scx200_hrt", + .rating = 250, + .read = read_hrt, + .mask = CLOCKSOURCE_MASK(32), + .is_continuous = 1, + /* mult, shift are set based on mhz27 flag */ +}; + +static int __init init_hrt_clocksource(void) +{ + /* Make sure scx200 has initializedd 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")) { + printk(KERN_WARNING NAME ": unable to lock timer region\n"); + return -ENODEV; + } + + /* write timer config */ + outb(HR_TMEN | (mhz27) ? HR_TMCLKSEL : 0, + scx200_cb_base + SCx200_TMCNFG_OFFSET); + + if (mhz27) { + cs_hrt.shift = HRT_SHIFT_27; + cs_hrt.mult = clocksource_hz2mult((HRT_FREQ + ppm) * 27, + cs_hrt.shift); + } else { + cs_hrt.shift = HRT_SHIFT_1; + cs_hrt.mult = clocksource_hz2mult(HRT_FREQ + ppm, + cs_hrt.shift); + } + printk(KERN_INFO "enabling scx200 high-res timer (%s MHz +%d ppm)\n", + mhz27 ? "27":"1", ppm); + + return clocksource_register(&cs_hrt); +} + +module_init(init_hrt_clocksource); + +MODULE_AUTHOR("Jim Cromie "); +MODULE_DESCRIPTION("clocksource on SCx200 HiRes Timer"); +MODULE_LICENSE("GPL"); -- cgit