From 59d01a7aaae9dc52790bbe49ba1bafb9c975168a Mon Sep 17 00:00:00 2001 From: Wu Zhangjin Date: Thu, 17 Dec 2009 21:48:53 +0800 Subject: [PATCH] MIPS: r4k: Add a high resolution sched_clock() commit 7ac72cc54968c4820052f39de5b9b7891f625498 in tip. (v8 -> v9: O Make it depends on 64BIT for the current mips_sched_clock() only support 64bit currently. v7 -> v8: O Make it works with the exisiting clocksource_mips.mult, clocksource_mips.shift and copes with the 64bit calculation's overflow problem with the method introduced by David Daney in "MIPS: Octeon: Use non-overflowing arithmetic in sched_clock". To reduce the duplication, I have abstracted an inline mips_sched_clock() function to arch/mips/include/asm/time.h from arch/mips/cavium-octeon/csrc-octeon.c. v6 -> v7: O Make it depends on !CPU_FREQ and CPU_HAS_FIXED_C0_COUNT This sched_clock() is only available with the processor has fixed cp0 MIPS count register or even has dynamic cp0 MIPS count register but with CPU_FREQ disabled. NOTE: If your processor has fixed c0 count, please select CPU_HAS_FIXED_C0_COUNT for it and send a related patch to Ralf. v5 -> v6: o hard-codes the cycle2ns_scale_factor as 8 for 30(cs->shift) is too big. With 30, the return value of sched_clock() will also overflow quickly. o moves the sched_clock() back into csrc-r4k.c as David and Sergei recommended. o inits c0 count as zero for PRINTK_TIME=y. o drops the HR_SCHED_CLCOK option for the current sched_clock() is stable enough to replace the jiffies based one. ) This patch adds a cnt32_to_63() and MIPS c0 count based sched_clock(), which provides high resolution. Without it, the Ftrace for MIPS will give useless timestamp information. Because cnt32_to_63() needs to be called at least once per half period to work properly, Differ from the old version, this v2 revision set up a kernel timer to ensure the requirement of some MIPSs which have short c0 count period. And also, we init the c0 count as ZERO(just as jiffies does) in time_init() before plat_time_init(), without it, PRINTK_TIME=y will get wrong timestamp information. (NOTE: some platforms have initiazlied c0 count as zero, but some not, this may introduce some duplication, perhaps a new patch is needed to remove the initialized of c0 count in the platforms later?) This is originally from arch/arm/plat-orion/time.c This revision works well for function graph tracer now, and also, PRINTK_TIME=y will get normal timestamp informatin. Signed-off-by: Wu Zhangjin Signed-off-by: Paul Gortmaker --- arch/mips/Kconfig | 13 ++++++++++++ arch/mips/kernel/csrc-r4k.c | 45 +++++++++++++++++++++++++++++++++++++++++++ arch/mips/kernel/time.c | 5 ++++ 3 files changed, 63 insertions(+), 0 deletions(-) diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig index 7e6fd1c..10b2923 100644 --- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -1965,6 +1965,19 @@ config NR_CPUS source "kernel/time/Kconfig" # +# High Resolution sched_clock() support +# + +config CPU_HAS_FIXED_C0_COUNT + bool + +config CPU_SUPPORTS_HR_SCHED_CLOCK + bool + depends on CPU_HAS_FIXED_C0_COUNT || !CPU_FREQ + depends on 64BIT + default y + +# # Timer Interrupt Frequency Configuration # diff --git a/arch/mips/kernel/csrc-r4k.c b/arch/mips/kernel/csrc-r4k.c index e95a3cd..89473ba 100644 --- a/arch/mips/kernel/csrc-r4k.c +++ b/arch/mips/kernel/csrc-r4k.c @@ -6,7 +6,9 @@ * Copyright (C) 2007 by Ralf Baechle */ #include +#include #include +#include #include @@ -22,6 +24,47 @@ static struct clocksource clocksource_mips = { .flags = CLOCK_SOURCE_IS_CONTINUOUS, }; +#ifdef CONFIG_CPU_SUPPORTS_HR_SCHED_CLOCK +/* + * MIPS sched_clock implementation. + * + * Because the hardware timer period is quite short and because cnt32_to_63() + * needs to be called at least once per half period to work properly, a kernel + * timer is set up to ensure this requirement is always met. + * + * Please refer to include/linux/cnt32_to_63.h, arch/arm/plat-orion/time.c and + * arch/mips/include/asm/time.h (mips_sched_clock) + */ +unsigned long long notrace sched_clock(void) +{ + u64 cnt = cnt32_to_63(read_c0_count()); + + if (cnt & 0x8000000000000000) + cnt &= 0x7fffffffffffffff; + + return mips_sched_clock(&clocksource_mips, cnt); +} + +static struct timer_list cnt32_to_63_keepwarm_timer; + +static void cnt32_to_63_keepwarm(unsigned long data) +{ + mod_timer(&cnt32_to_63_keepwarm_timer, round_jiffies(jiffies + data)); + sched_clock(); +} +#endif + +static inline void setup_hres_sched_clock(unsigned long clock) +{ +#ifdef CONFIG_CPU_SUPPORTS_HR_SCHED_CLOCK + unsigned long data; + + data = 0x80000000UL / clock * HZ; + setup_timer(&cnt32_to_63_keepwarm_timer, cnt32_to_63_keepwarm, data); + mod_timer(&cnt32_to_63_keepwarm_timer, round_jiffies(jiffies + data)); +#endif +} + int __init init_r4k_clocksource(void) { if (!cpu_has_counter || !mips_hpt_frequency) @@ -32,6 +75,8 @@ int __init init_r4k_clocksource(void) clocksource_set_clock(&clocksource_mips, mips_hpt_frequency); + setup_hres_sched_clock(mips_hpt_frequency); + clocksource_register(&clocksource_mips); return 0; diff --git a/arch/mips/kernel/time.c b/arch/mips/kernel/time.c index fb74974..86cf18a 100644 --- a/arch/mips/kernel/time.c +++ b/arch/mips/kernel/time.c @@ -119,6 +119,11 @@ static __init int cpu_has_mfc0_count_bug(void) void __init time_init(void) { +#ifdef CONFIG_CPU_SUPPORTS_HR_SCHED_CLOCK + if (!mips_clockevent_init() || !cpu_has_mfc0_count_bug()) + write_c0_count(0); +#endif + plat_time_init(); if (!mips_clockevent_init() || !cpu_has_mfc0_count_bug()) -- 1.7.0.4