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

Commit 70264367a243 ("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>

3 files changed, 6 insertions, 7 deletions

diff --git a/arch/arm/include/asm/delay.h b/arch/arm/include/asm/delay.h
index 720799fd3a81..dff714d886d5 100644
--- a/arch/arm/include/asm/delay.h
+++ b/arch/arm/include/asm/delay.h
@@ -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)
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 79078edbb9bc..1f2ccccaf009 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -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;
diff --git a/arch/arm/lib/delay.c b/arch/arm/lib/delay.c
index 6b93f6a1a3c7..64dbfa57204a 100644
--- a/arch/arm/lib/delay.c
+++ b/arch/arm/lib/delay.c
@@ -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");