3.8-stable review patch. If anyone has any objections, please let me know.
------------------ From: Nicolas Pitre <[email protected]> commit 70264367a243a68b1d5636ffb570183449803cbe upstream. 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 <[email protected]> Signed-off-by: Nicolas Pitre <[email protected]> Tested-by: Viresh Kumar <[email protected]> Acked-by: Liviu Dudau <[email protected]> Signed-off-by: Russell King <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/arm/include/asm/delay.h | 1 + arch/arm/kernel/smp.c | 3 +++ arch/arm/lib/delay.c | 1 + 3 files changed, 5 insertions(+) --- 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) --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -693,6 +693,9 @@ static int cpufreq_callback(struct notif 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; --- a/arch/arm/lib/delay.c +++ b/arch/arm/lib/delay.c @@ -77,6 +77,7 @@ void __init register_current_timer_delay 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"); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
