ARM: 7653/2: do not scale loops_per_jiffy when using a constant delay clock
When udelay() is implemented using an architected timer, it is wrong to scale loops_per_jiffy when changing the CPU clock frequency since the timer clock remains constant. The lpj should probably become an implementation detail relevant to the CPU loop based delay routine only and more confined to it. In the mean time this is the minimal fix needed to have expected delays with the timer based implementation when cpufreq is also in use. Reported-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Nicolas Pitre <nico@linaro.org> Tested-by: Viresh Kumar <viresh.kumar@linaro.org> Acked-by: Liviu Dudau <Liviu.Dudau@arm.com> Cc: stable@vger.kernel.org Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
parent
7c4e9ced42
commit
70264367a2
|
@ -24,6 +24,7 @@ extern struct arm_delay_ops {
|
||||||
void (*delay)(unsigned long);
|
void (*delay)(unsigned long);
|
||||||
void (*const_udelay)(unsigned long);
|
void (*const_udelay)(unsigned long);
|
||||||
void (*udelay)(unsigned long);
|
void (*udelay)(unsigned long);
|
||||||
|
bool const_clock;
|
||||||
} arm_delay_ops;
|
} arm_delay_ops;
|
||||||
|
|
||||||
#define __delay(n) arm_delay_ops.delay(n)
|
#define __delay(n) arm_delay_ops.delay(n)
|
||||||
|
|
|
@ -693,6 +693,9 @@ static int cpufreq_callback(struct notifier_block *nb,
|
||||||
if (freq->flags & CPUFREQ_CONST_LOOPS)
|
if (freq->flags & CPUFREQ_CONST_LOOPS)
|
||||||
return NOTIFY_OK;
|
return NOTIFY_OK;
|
||||||
|
|
||||||
|
if (arm_delay_ops.const_clock)
|
||||||
|
return NOTIFY_OK;
|
||||||
|
|
||||||
if (!per_cpu(l_p_j_ref, cpu)) {
|
if (!per_cpu(l_p_j_ref, cpu)) {
|
||||||
per_cpu(l_p_j_ref, cpu) =
|
per_cpu(l_p_j_ref, cpu) =
|
||||||
per_cpu(cpu_data, cpu).loops_per_jiffy;
|
per_cpu(cpu_data, cpu).loops_per_jiffy;
|
||||||
|
|
|
@ -77,6 +77,7 @@ void __init register_current_timer_delay(const struct delay_timer *timer)
|
||||||
arm_delay_ops.delay = __timer_delay;
|
arm_delay_ops.delay = __timer_delay;
|
||||||
arm_delay_ops.const_udelay = __timer_const_udelay;
|
arm_delay_ops.const_udelay = __timer_const_udelay;
|
||||||
arm_delay_ops.udelay = __timer_udelay;
|
arm_delay_ops.udelay = __timer_udelay;
|
||||||
|
arm_delay_ops.const_clock = true;
|
||||||
delay_calibrated = true;
|
delay_calibrated = true;
|
||||||
} else {
|
} else {
|
||||||
pr_info("Ignoring duplicate/late registration of read_current_timer delay\n");
|
pr_info("Ignoring duplicate/late registration of read_current_timer delay\n");
|
||||||
|
|
Loading…
Reference in New Issue