From mboxrd@z Thu Jan 1 00:00:00 1970 From: tomasz.figa@gmail.com (Tomasz Figa) Date: Sun, 28 Aug 2011 02:49:58 +0200 Subject: [PATCH 5/5] ARM: s3c64xx: Add optional local sched_clock implementation. Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org This patch adds local sched_clock implementation using the PWM timer used for generic clock source and a Kconfig option to enable/disable it. Signed-off-by: Tomasz Figa --- arch/arm/mach-s3c64xx/Kconfig | 8 ++++++++ arch/arm/mach-s3c64xx/time.c | 28 +++++++++++++++++++++++++++- 2 files changed, 35 insertions(+), 1 deletions(-) diff --git a/arch/arm/mach-s3c64xx/Kconfig b/arch/arm/mach-s3c64xx/Kconfig index 2db76fd..e11dd9b 100644 --- a/arch/arm/mach-s3c64xx/Kconfig +++ b/arch/arm/mach-s3c64xx/Kconfig @@ -33,6 +33,14 @@ config S3C64XX_GENERIC_CLOCKEVENTS on S3C6400/S3C6410 SoCs using PWM timers 3 and 4 instead of standard periodic tick using PWM timer 4. +config S3C64XX_SCHED_CLOCK + bool "Use PWM clock source for scheduler clock" + depends on S3C64XX_GENERIC_CLOCKEVENTS + select HAVE_SCHED_CLOCK + help + This option enables local scheduler clock implementation + using PWM clock source. + config S3C64XX_ARCH_USES_GETTIMEOFFSET def_bool y if !S3C64XX_GENERIC_CLOCKEVENTS select ARCH_USES_GETTIMEOFFSET diff --git a/arch/arm/mach-s3c64xx/time.c b/arch/arm/mach-s3c64xx/time.c index 4fa57f0..4a78844 100644 --- a/arch/arm/mach-s3c64xx/time.c +++ b/arch/arm/mach-s3c64xx/time.c @@ -28,6 +28,7 @@ #include #include +#include #include #include #include @@ -241,6 +242,29 @@ static void s3c64xx_clocksource_resume(struct clocksource *cs) s3c64xx_pwm_start(PWM_SOURCE, PERIODIC); } +#ifdef CONFIG_S3C64XX_SCHED_CLOCK +/* + * Override the global weak sched_clock symbol with this + * local implementation which uses the clocksource to get some + * better resolution when scheduling the kernel. We accept that + * this wraps around for now, since it is just a relative time + * stamp. (Inspired by U300 implementation.) + */ +static DEFINE_CLOCK_DATA(cd); + +unsigned long long notrace sched_clock(void) +{ + return cyc_to_sched_clock(&cd, + ~__raw_readl(S3C2410_TCNTO(PWM_SOURCE)), TCNT_MAX); +} + +static void notrace s3c64xx_update_sched_clock(void) +{ + update_sched_clock(&cd, + ~__raw_readl(S3C2410_TCNTO(PWM_SOURCE)), (u32)~0); +} +#endif /* CONFIG_S3C64XX_SCHED_CLOCK */ + static struct clocksource pwm_clocksource = { .name = "s3c64xx_clksrc", .rating = 250, @@ -258,7 +282,9 @@ static void __init s3c64xx_clocksource_init(void) s3c64xx_pwm_init(PWM_SOURCE, TCNT_MAX); s3c64xx_pwm_start(PWM_SOURCE, PERIODIC); - +#ifdef CONFIG_S3C64XX_SCHED_CLOCK + init_sched_clock(&cd, s3c64xx_update_sched_clock, 32, clock_rate); +#endif /* CONFIG_S3C64XX_SCHED_CLOCK */ if (clocksource_register_hz(&pwm_clocksource, clock_rate)) panic("%s: can't register clocksource\n", pwm_clocksource.name); } -- 1.7.6.1