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ARM: 7538/1: delay: add registration mechanism for delay timer sources

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The current timer-based delay loop relies on the architected timer to
initiate the switch away from the polling-based implementation. This is
unfortunate for platforms without the architected timers but with a
suitable delay source (that is, constant frequency, always powered-up
and ticking as long as the CPUs are online).

This patch introduces a registration mechanism for the delay timer
(which provides an unconditional read_current_timer implementation) and
updates the architected timer code to use the new interface.

Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Jonathan Austin <jonathan.austin@arm.com>
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:
Jonathan Austin
2012-09-21 18:51:44 +01:00
committed by Russell King
parent a1b2dde704
commit 56942fec06
5 changed files with 43 additions and 24 deletions
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34
arch/arm/lib/delay.c
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@@ -34,7 +34,18 @@ struct arm_delay_ops arm_delay_ops = {
.udelay = __loop_udelay,
};
#ifdef ARCH_HAS_READ_CURRENT_TIMER
static const struct delay_timer *delay_timer;
static bool delay_calibrated;
int read_current_timer(unsigned long *timer_val)
{
if (!delay_timer)
return -ENXIO;
*timer_val = delay_timer->read_current_timer();
return 0;
}
static void __timer_delay(unsigned long cycles)
{
cycles_t start = get_cycles();
@@ -55,17 +66,24 @@ static void __timer_udelay(unsigned long usecs)
__timer_const_udelay(usecs * UDELAY_MULT);
}
void __init init_current_timer_delay(unsigned long freq)
void __init register_current_timer_delay(const struct delay_timer *timer)
{
pr_info("Switching to timer-based delay loop\n");
lpj_fine = freq / HZ;
arm_delay_ops.delay = __timer_delay;
arm_delay_ops.const_udelay = __timer_const_udelay;
arm_delay_ops.udelay = __timer_udelay;
if (!delay_calibrated) {
pr_info("Switching to timer-based delay loop\n");
delay_timer = timer;
lpj_fine = timer->freq / HZ;
loops_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");
}
}
unsigned long __cpuinit calibrate_delay_is_known(void)
{
delay_calibrated = true;
return lpj_fine;
}
#endif