From 70264367a243a68b1d5636ffb570183449803cbe Mon Sep 17 00:00:00 2001 From: Nicolas Pitre Date: Mon, 18 Feb 2013 16:36:13 +0100 Subject: [PATCH] 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 Signed-off-by: Nicolas Pitre Tested-by: Viresh Kumar Acked-by: Liviu Dudau Cc: stable@vger.kernel.org Signed-off-by: Russell King --- arch/arm/include/asm/delay.h | 1 + arch/arm/kernel/smp.c | 3 +++ arch/arm/lib/delay.c | 1 + 3 files changed, 5 insertions(+) diff --git a/arch/arm/include/asm/delay.h b/arch/arm/include/asm/delay.h index ab98fdd083bd..720799fd3a81 100644 --- a/arch/arm/include/asm/delay.h +++ b/arch/arm/include/asm/delay.h @@ -24,6 +24,7 @@ extern struct arm_delay_ops { void (*delay)(unsigned long); void (*const_udelay)(unsigned long); void (*udelay)(unsigned long); + bool const_clock; } arm_delay_ops; #define __delay(n) arm_delay_ops.delay(n) diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index 84f4cbf652e5..58af91c2a2f7 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -693,6 +693,9 @@ 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; diff --git a/arch/arm/lib/delay.c b/arch/arm/lib/delay.c index 0dc53854a5d8..6b93f6a1a3c7 100644 --- a/arch/arm/lib/delay.c +++ b/arch/arm/lib/delay.c @@ -77,6 +77,7 @@ void __init register_current_timer_delay(const struct delay_timer *timer) 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"); -- 2.39.2