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Commit b040614c authored by Olof Johansson's avatar Olof Johansson
Browse files

Merge tag 'tegra-for-3.17-delay-timer' of... 

Merge tag 'tegra-for-3.17-delay-timer' of git://git.kernel.org/pub/scm/linux/kernel/git/tegra/linux into next/soc

Merge "ARM: tegra: use us counter as delay timer" from Stephen Warren:

Tegra has a micro-second counter whose rate doesn't vary with cpufreq
changes. Register it so it can be used as the delay timer, so delays
aren't influenced by cpufreq.

* tag 'tegra-for-3.17-delay-timer' of git://git.kernel.org/pub/scm/linux/kernel/git/tegra/linux

:
  clocksource: tegra: Use us counter as delay timer
  ARM: choose highest resolution delay timer
  kernel: add calibration_delay_done()

Signed-off-by: default avatarOlof Johansson <olof@lixom.net>
parents 21760aed 0ff36b4f

arch/arm/lib/delay.c

+22 −4
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ 
 * Author: Will Deacon <will.deacon@arm.com>

 */



#include <linux/clocksource.h>

#include <linux/delay.h>

#include <linux/init.h>

#include <linux/kernel.h>
@@ -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;

}

drivers/clocksource/tegra20_timer.c

+13 −0
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ 
#include <linux/of_address.h>

#include <linux/of_irq.h>

#include <linux/sched_clock.h>

#include <linux/delay.h>



#include <asm/mach/time.h>

#include <asm/smp_twd.h>
@@ -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);

init/calibrate.c

+11 −0
Original line number Diff line number Diff line
@@ -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();

}