| From 7ac72cc54968c4820052f39de5b9b7891f625498 Mon Sep 17 00:00:00 2001 |
| From: Wu Zhangjin <wuzhangjin@gmail.com> |
| 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 <wuzhangjin@gmail.com> |
| |
| diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig |
| index 8b5d174..e87a850 100644 |
| --- a/arch/mips/Kconfig |
| +++ b/arch/mips/Kconfig |
| @@ -1934,6 +1934,19 @@ 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 <linux/clocksource.h> |
| +#include <linux/cnt32_to_63.h> |
| #include <linux/init.h> |
| +#include <linux/timer.h> |
| |
| #include <asm/time.h> |
| |
| @@ -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()) |
| -- |
| 1.7.1.1 |
| |