From mboxrd@z Thu Jan 1 00:00:00 1970 From: l.pinguin@gmail.com (Remy Bohmer) Date: Sun, 31 Jul 2011 17:03:13 +0200 Subject: [PATCH] Add sched_clock to AT91 TCB clocksource driver Message-ID: <1312124593-6088-1-git-send-email-linux@bohmer.net> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On AT91 there is no architecture specific sched_clock() implementation, so the default fallback is used. This fallback uses the jiffie counter as sched_clock(). There is NO standard clocksource available that is accurate enough, except the TC-based clocksource implementation. Therefor this implementation is used as base for the sched_clock(). This clocksource offers sub-millisecond time-stamping. (< 200 ns) Signed-off-by: Remy Bohmer --- arch/arm/Kconfig | 1 + arch/arm/kernel/sched_clock.c | 7 +++++++ drivers/clocksource/tcb_clksrc.c | 23 +++++++++++++++++++++++ 3 files changed, 31 insertions(+), 0 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 9adc278..e0563a7 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -296,6 +296,7 @@ config ARCH_AT91 select HAVE_CLK select CLKDEV_LOOKUP select ARM_PATCH_PHYS_VIRT if MMU + select HAVE_SCHED_CLOCK if ATMEL_TCB_CLKSRC help This enables support for systems based on the Atmel AT91RM9200, AT91SAM9 and AT91CAP9 processors. diff --git a/arch/arm/kernel/sched_clock.c b/arch/arm/kernel/sched_clock.c index 9a46370..f9028e4 100644 --- a/arch/arm/kernel/sched_clock.c +++ b/arch/arm/kernel/sched_clock.c @@ -20,6 +20,13 @@ static void (*sched_clock_update_fn)(void); static void sched_clock_poll(unsigned long wrap_ticks) { + /* + * The sched_clock_update_fn may be initialised AFTER first call to + * time_init() + */ + if (unlikely(!sched_clock_update_fn)) + return; + mod_timer(&sched_clock_timer, round_jiffies(jiffies + wrap_ticks)); sched_clock_update_fn(); } diff --git a/drivers/clocksource/tcb_clksrc.c b/drivers/clocksource/tcb_clksrc.c index 79c47e8..d6069b3 100644 --- a/drivers/clocksource/tcb_clksrc.c +++ b/drivers/clocksource/tcb_clksrc.c @@ -11,6 +11,7 @@ #include #include +#include /* * We're configured to use a specific TC block, one that's not hooked @@ -210,6 +211,23 @@ static void __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx) #endif +static DEFINE_CLOCK_DATA(cd); + +unsigned long long notrace sched_clock(void) +{ + if (likely(tcaddr)) { + cycle_t cyc = tc_get_cycles(&clksrc); + return cyc_to_sched_clock(&cd, cyc, (u32)~0); + } + return 0; +} + +static void notrace tcb_update_sched_clock(void) +{ + cycle_t cyc = tc_get_cycles(&clksrc); + update_sched_clock(&cd, cyc, (u32)~0); +} + static int __init tcb_clksrc_init(void) { static char bootinfo[] __initdata @@ -297,6 +315,11 @@ static int __init tcb_clksrc_init(void) /* channel 2: periodic and oneshot timer support */ setup_clkevents(tc, clk32k_divisor_idx); + /* Now prepare the sched_clock support */ + init_sched_clock(&cd, tcb_update_sched_clock, 32, divided_rate); + sched_clock_postinit(); + return 0; } arch_initcall(tcb_clksrc_init); + -- 1.7.4.1