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ARM: 7685/1: delay: use private ticks_per_jiffy field for timer-based delay ops

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Commit 70264367a2 ("ARM: 7653/2: do not scale loops_per_jiffy when
using a constant delay clock") fixed a problem with our timer-based
delay loop, where loops_per_jiffy is scaled by cpufreq yet used directly
by the timer delay ops.

This patch fixes the problem in a more elegant way by keeping a private
ticks_per_jiffy field in the delay ops, independent of loops_per_jiffy
and therefore not subject to scaling. The loop-based delay continues to
use loops_per_jiffy directly, as it should.

Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Will Deacon 2013-03-28 11:17:55 +01:00 committed by Russell King
parent 93dc68876b
commit 6f3d90e556
3 changed files with 6 additions and 7 deletions
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2
arch/arm/include/asm/delay.h
View file

@ -24,7 +24,7 @@ extern struct arm_delay_ops {
void (*delay)(unsigned long);
void (*const_udelay)(unsigned long);
void (*udelay)(unsigned long);
bool const_clock;
unsigned long ticks_per_jiffy;
} arm_delay_ops;
#define __delay(n) arm_delay_ops.delay(n)

3
arch/arm/kernel/smp.c
View file

@ -673,9 +673,6 @@ static int cpufreq_callback(struct notifier_block *nb,
if (freq->flags & CPUFREQ_CONST_LOOPS)
return NOTIFY_OK;
if (arm_delay_ops.const_clock)
return NOTIFY_OK;
if (!per_cpu(l_p_j_ref, cpu)) {
per_cpu(l_p_j_ref, cpu) =
per_cpu(cpu_data, cpu).loops_per_jiffy;

8
arch/arm/lib/delay.c
View file

@ -58,7 +58,7 @@ static void __timer_delay(unsigned long cycles)
static void __timer_const_udelay(unsigned long xloops)
{
unsigned long long loops = xloops;
loops *= loops_per_jiffy;
loops *= arm_delay_ops.ticks_per_jiffy;
__timer_delay(loops >> UDELAY_SHIFT);
}
@ -73,11 +73,13 @@ void __init register_current_timer_delay(const struct delay_timer *timer)
pr_info("Switching to timer-based delay loop\n");
delay_timer = timer;
lpj_fine = timer->freq / HZ;
loops_per_jiffy = lpj_fine;
/* 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;
arm_delay_ops.const_clock = true;
delay_calibrated = true;
} else {
pr_info("Ignoring duplicate/late registration of read_current_timer delay\n");