From e6639117d624d5c8f531d22456a69e38dc23c501 Mon Sep 17 00:00:00 2001 From: Peter De Schrijver Date: Thu, 12 Jun 2014 18:58:27 +0300 Subject: [PATCH 1/3] kernel: add calibration_delay_done() Add calibration_delay_done() call and dummy implementation. This allows architectures to stop accepting registrations for new timer based delay functions. Signed-off-by: Peter De Schrijver Acked-by: Russell King Signed-off-by: Stephen Warren --- init/calibrate.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/init/calibrate.c b/init/calibrate.c index 520702db9acc..ce635dccf3d9 100644 --- a/init/calibrate.c +++ b/init/calibrate.c @@ -262,6 +262,15 @@ unsigned long __attribute__((weak)) calibrate_delay_is_known(void) return 0; } +/* + * Indicate the cpu delay calibration is done. This can be used by + * architectures to stop accepting delay timer registrations after this point. + */ + +void __attribute__((weak)) calibration_delay_done(void) +{ +} + void calibrate_delay(void) { unsigned long lpj; @@ -301,4 +310,6 @@ void calibrate_delay(void) loops_per_jiffy = lpj; printed = true; + + calibration_delay_done(); } From 5930c1a1f7f8439883d0a2173c6ce51d577e36ec Mon Sep 17 00:00:00 2001 From: Peter De Schrijver Date: Thu, 12 Jun 2014 18:58:28 +0300 Subject: [PATCH 2/3] ARM: choose highest resolution delay timer In case there are several possible delay timers, choose the one with the highest resolution. This code relies on the fact secondary CPUs have not yet been brought online when register_current_timer_delay() is called. This is ensured by implementing calibration_delay_done(), Signed-off-by: Peter De Schrijver Acked-by: Russell King Signed-off-by: Stephen Warren --- arch/arm/lib/delay.c | 26 ++++++++++++++++++++++---- 1 file changed, 22 insertions(+), 4 deletions(-) diff --git a/arch/arm/lib/delay.c b/arch/arm/lib/delay.c index 5306de350133..312d43eb686a 100644 --- a/arch/arm/lib/delay.c +++ b/arch/arm/lib/delay.c @@ -19,6 +19,7 @@ * Author: Will Deacon */ +#include #include #include #include @@ -36,6 +37,7 @@ struct arm_delay_ops arm_delay_ops = { static const struct delay_timer *delay_timer; static bool delay_calibrated; +static u64 delay_res; int read_current_timer(unsigned long *timer_val) { @@ -47,6 +49,11 @@ int read_current_timer(unsigned long *timer_val) } EXPORT_SYMBOL_GPL(read_current_timer); +static inline u64 cyc_to_ns(u64 cyc, u32 mult, u32 shift) +{ + return (cyc * mult) >> shift; +} + static void __timer_delay(unsigned long cycles) { cycles_t start = get_cycles(); @@ -69,18 +76,24 @@ static void __timer_udelay(unsigned long usecs) void __init register_current_timer_delay(const struct delay_timer *timer) { - if (!delay_calibrated) { - pr_info("Switching to timer-based delay loop\n"); + u32 new_mult, new_shift; + u64 res; + + clocks_calc_mult_shift(&new_mult, &new_shift, timer->freq, + NSEC_PER_SEC, 3600); + res = cyc_to_ns(1ULL, new_mult, new_shift); + + if (!delay_calibrated && (!delay_res || (res < delay_res))) { + pr_info("Switching to timer-based delay loop, resolution %lluns\n", res); delay_timer = timer; lpj_fine = timer->freq / HZ; + delay_res = res; /* cpufreq may scale loops_per_jiffy, so keep a private copy */ arm_delay_ops.ticks_per_jiffy = lpj_fine; arm_delay_ops.delay = __timer_delay; arm_delay_ops.const_udelay = __timer_const_udelay; arm_delay_ops.udelay = __timer_udelay; - - delay_calibrated = true; } else { pr_info("Ignoring duplicate/late registration of read_current_timer delay\n"); } @@ -91,3 +104,8 @@ unsigned long calibrate_delay_is_known(void) delay_calibrated = true; return lpj_fine; } + +void calibration_delay_done(void) +{ + delay_calibrated = true; +} From 0ff36b4f479ec8e0cd9b7a919ab877f2d553cd30 Mon Sep 17 00:00:00 2001 From: Peter De Schrijver Date: Thu, 12 Jun 2014 18:58:29 +0300 Subject: [PATCH 3/3] clocksource: tegra: Use us counter as delay timer All Tegra SoCs have a freerunning microsecond counter which can be used as a delay timer. Signed-off-by: Peter De Schrijver Acked-by: Russell King Signed-off-by: Stephen Warren --- drivers/clocksource/tegra20_timer.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/drivers/clocksource/tegra20_timer.c b/drivers/clocksource/tegra20_timer.c index d1869f02051c..d2616ef16770 100644 --- a/drivers/clocksource/tegra20_timer.c +++ b/drivers/clocksource/tegra20_timer.c @@ -27,6 +27,7 @@ #include #include #include +#include #include #include @@ -53,6 +54,8 @@ static void __iomem *rtc_base; static struct timespec persistent_ts; static u64 persistent_ms, last_persistent_ms; +static struct delay_timer tegra_delay_timer; + #define timer_writel(value, reg) \ __raw_writel(value, timer_reg_base + (reg)) #define timer_readl(reg) \ @@ -139,6 +142,11 @@ static void tegra_read_persistent_clock(struct timespec *ts) *ts = *tsp; } +static unsigned long tegra_delay_timer_read_counter_long(void) +{ + return readl(timer_reg_base + TIMERUS_CNTR_1US); +} + static irqreturn_t tegra_timer_interrupt(int irq, void *dev_id) { struct clock_event_device *evt = (struct clock_event_device *)dev_id; @@ -206,6 +214,11 @@ static void __init tegra20_init_timer(struct device_node *np) BUG(); } + tegra_delay_timer.read_current_timer = + tegra_delay_timer_read_counter_long; + tegra_delay_timer.freq = 1000000; + register_current_timer_delay(&tegra_delay_timer); + ret = setup_irq(tegra_timer_irq.irq, &tegra_timer_irq); if (ret) { pr_err("Failed to register timer IRQ: %d\n", ret);