From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S270517AbTGSIBU (ORCPT ); Sat, 19 Jul 2003 04:01:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S270515AbTGSIBU (ORCPT ); Sat, 19 Jul 2003 04:01:20 -0400 Received: from natsmtp00.webmailer.de ([192.67.198.74]:28839 "EHLO post.webmailer.de") by vger.kernel.org with ESMTP id S270519AbTGSIAx (ORCPT ); Sat, 19 Jul 2003 04:00:53 -0400 Date: Sat, 19 Jul 2003 10:14:07 +0200 From: Dominik Brodowski To: linux-kernel@vger.kernel.org, arjanv@redhat.com, johnstul@us.ibm.com Subject: [RFC][PATCH 2.6] PM Timer as primary timing source on i386 Message-ID: <20030719081407.GA2665@brodo.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org This patch implements support for a different timing source for the i386 architecture, the Power Management Timer (PMTMR). It offers correct results with a ~3.6MHz resolution even during aggressive Powermanagement like ACPI C-State transitions, throttling and/or frequency scaling. It is based partly on Arjan's patch for 2.4. arch/i386/Kconfig | 10 + arch/i386/kernel/time.c | 1 arch/i386/kernel/timers/Makefile | 1 arch/i386/kernel/timers/timer_pm.c | 188 +++++++++++++++++++++++++++++++++++++ 4 files changed, 200 insertions(+) diff -ruN linux-original/arch/i386/Kconfig linux/arch/i386/Kconfig --- linux-original/arch/i386/Kconfig 2003-07-14 17:13:27.000000000 +0200 +++ linux/arch/i386/Kconfig 2003-07-19 09:42:33.000000000 +0200 @@ -506,6 +506,16 @@ depends on (MWINCHIP3D || MWINCHIP2 || MCRUSOE || MCYRIXIII || MK7 || MK6 || MPENTIUM4 || MPENTIUMIII || MPENTIUMII || M686 || M586MMX || M586TSC || MK8 || MVIAC3_2) && !X86_NUMAQ default y +config X86_PM_TIMER + tristate "Use Power Management Timer (PMTMR) as primary timing source" + depends on ACPI_BUS + help + The Power Management Timer (PMTMR) is available on all + ACPI-capable systems. it provides a reliable timing source + which does not get affected by powermanagement features + (e.g. aggressive idling, throttling or frequency scaling), + unlike the commonly used Time Stamp Counter (TSC) timing source. + config X86_MCE bool "Machine Check Exception" ---help--- diff -ruN linux-original/arch/i386/kernel/time.c linux/arch/i386/kernel/time.c --- linux-original/arch/i386/kernel/time.c 2003-07-14 17:13:27.000000000 +0200 +++ linux/arch/i386/kernel/time.c 2003-07-18 17:50:12.000000000 +0200 @@ -81,6 +81,7 @@ EXPORT_SYMBOL(i8253_lock); struct timer_opts *cur_timer = &timer_none; +EXPORT_SYMBOL(cur_timer); /* * This version of gettimeofday has microsecond resolution diff -ruN linux-original/arch/i386/kernel/timers/Makefile linux/arch/i386/kernel/timers/Makefile --- linux-original/arch/i386/kernel/timers/Makefile 2003-06-15 12:16:15.000000000 +0200 +++ linux/arch/i386/kernel/timers/Makefile 2003-07-19 09:22:39.000000000 +0200 @@ -5,3 +5,4 @@ obj-y := timer.o timer_none.o timer_tsc.o timer_pit.o obj-$(CONFIG_X86_CYCLONE_TIMER) += timer_cyclone.o +obj-$(CONFIG_X86_PM_TIMER) += timer_pm.o diff -ruN linux-original/arch/i386/kernel/timers/timer_pm.c linux/arch/i386/kernel/timers/timer_pm.c --- linux-original/arch/i386/kernel/timers/timer_pm.c 1970-01-01 01:00:00.000000000 +0100 +++ linux/arch/i386/kernel/timers/timer_pm.c 2003-07-19 09:50:57.000000000 +0200 @@ -0,0 +1,188 @@ +/* + * (C) Dominik Brodowski 2003 + * + * Driver to use the Power Management Timer (PMTMR) available in some + * southbridges as primary timing source for the Linux kernel. + * + * based on parts of linux/drivers/acpi/hardware/hwtimer.c and of timer_pit.c, + * and on Arjan van de Ven's implementation for 2.4. + * + * This file is licensed under the GPL v2. + */ + + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +/* The I/O port the PMTMR resides at */ +static u32 pmtmr_ioport = 0; + +/* value of the Power timer at last timer interrupt */ +static u32 offset_tick; + +/* forward declaration of our timer_opts struct */ +struct timer_opts timer_pmtmr; +static void mark_offset_pmtmr(void); + +/************ detection of the I/O port *****************/ + +/* + * The PMTMR I/O port can be detected using the following methods: + * + * a) Scan the PCI bus for the device the PMTMR is located at [e.g. PIIX4 southbridge], + * locate its I/O port range, and then use a table-lookup to find the I/O port + * (offset) for the PMTMR for this device. + * While this provides some safety from buggy BIOSes, it is also very chipset-specific + * and only available once the PCI devices are properly enabled, e.g. very late during + * the boot process. Another timing source needs to be used in between. However, as this + * approach is independent of ACPI and CONFIG_ACPI, it might be a good solution for some + * very broken systems. + * This method is not implemented yet. + * + * b) Ask the ACPI subsystem's FADT. While this is the easiest approach, it also means that + * this timer is only available _late_ in the boot process, only after the ACPI subsystem + * has been initialized (which is a subsys_initcall). However, the timing sources are set + * up already earlier. This means that we need to use the TSC or the PIT intermediately until + * this code replaces the earlier used timer with the PMTMR [see mark_offset_and_replace() foir + * details on this]. + * This method is implemented. + * + * c) Parse the ACPI FADT here, too. This means that this code could be independend of CONFIG_ACPI, + * but it would cause a lot of code duplication between the ACPI subsystem and this file. However, + * as this could mean that the PMTMR can be used immediately, without having to rely on alternate + * timing sources first. + * This method is not implemented yet. + */ + +static void mark_offset_and_replace(void) +{ + cur_timer = &timer_pmtmr; + mark_offset_pmtmr(); +} + +/* method b) */ + +#include +#include + +struct timer_opts *prev_timer; + +static int __init pmtimer_init(void) +{ + int ret; + + ret = acpi_get_timer(&offset_tick); + if (ret) { + printk(KERN_ERR "acpi_get_timer failed\n"); + return -EINVAL; + } + + if (acpi_fadt.xpm_tmr_blk.address_space_id != ACPI_ADR_SPACE_SYSTEM_IO) { + printk(KERN_INFO "ACPI PM timer is not at IO port -- error\n"); + return -EINVAL; + } + + pmtmr_ioport = acpi_fadt.xpm_tmr_blk.address; + if (!pmtmr_ioport) { + printk(KERN_INFO "ACPI PM timer invalid IO port\n"); + return -EINVAL; + } + + printk(KERN_INFO "Using ACPI PM timer at 0x%x as timing source.\n", pmtmr_ioport); + + prev_timer = cur_timer; + cur_timer->mark_offset = mark_offset_and_replace; + + return 0; +} +fs_initcall(pmtimer_init); + +static void __exit pmtimer_exit(void) +{ + cur_timer = prev_timer; +} +module_exit(pmtimer_exit); + + +/************ actual timing code *****************/ + +/* + * this gets called during each timer interrupt + */ +static void mark_offset_pmtmr(void) +{ + offset_tick = inl(pmtmr_ioport); + offset_tick &= 0xFFFFFF; /* limit it to 24 bits */ + return; +} + +/* + * would it be desirable to have a ~279 nanosecond resolution? + */ +static unsigned long long monotonic_clock_pmtmr(void) +{ + return 0; +} + +/* + * copied from delay_pit + */ +static void delay_pmtmr(unsigned long loops) +{ + int d0; + __asm__ __volatile__( + "\tjmp 1f\n" + ".align 16\n" + "1:\tjmp 2f\n" + ".align 16\n" + "2:\tdecl %0\n\tjns 2b" + :"=&a" (d0) + :"0" (loops)); +} + +/* + * get the offset (in microseconds) from the last call to mark_offset() + */ +static unsigned long get_offset_pmtmr(void) +{ + u32 now, offset, delta = 0; + + offset = offset_tick; + now = inl(pmtmr_ioport); + now &= 0xFFFFFF; + if (offset < now) + delta = now - offset; + else if (offset > now) + delta = (0xFFFFFF - offset) + now; + + /* The Power Management Timer ticks at 3.579545 ticks per microsecond. + * 1 / PM_TIMER_FREQUENCY == 0.27936511 =~ 286/1024 [error: 0.024%] + * + * Even with HZ = 100, delta is at maximum 35796 ticks, so it can + * easily be multiplied with 286 (=0x11E) without having to fear + * u32 overflows. + */ + delta *= 286; + return (unsigned long) (delta >> 10); +} + +/* acpi timer_opts struct */ +struct timer_opts timer_pmtmr = { + .init = NULL, + .mark_offset = mark_offset_pmtmr, + .get_offset = get_offset_pmtmr, + .monotonic_clock = monotonic_clock_pmtmr, + .delay = delay_pmtmr, +}; + + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Dominik Brodowski "); +MODULE_DESCRIPTION("Power Management Timer (PMTMR) as primary timing source for i386");