| Message ID | 1364235499-17797-1-git-send-email-will.deacon@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, 25 Mar 2013, Will Deacon wrote: > 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. > > Signed-off-by: Will Deacon <will.deacon@arm.com> Acked-by: Nicolas Pitre <nico@linaro.org> > --- > arch/arm/include/asm/delay.h | 2 +- > arch/arm/kernel/smp.c | 3 --- > arch/arm/lib/delay.c | 8 +++++--- > 3 files changed, 6 insertions(+), 7 deletions(-) > > diff --git a/arch/arm/include/asm/delay.h b/arch/arm/include/asm/delay.h > index 720799f..dff714d 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 79078ed..1f2cccc 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 6b93f6a..64dbfa5 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"); > -- > 1.8.0 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
diff --git a/arch/arm/include/asm/delay.h b/arch/arm/include/asm/delay.h index 720799f..dff714d 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 79078ed..1f2cccc 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 6b93f6a..64dbfa5 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");
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. Signed-off-by: Will Deacon <will.deacon@arm.com> --- arch/arm/include/asm/delay.h | 2 +- arch/arm/kernel/smp.c | 3 --- arch/arm/lib/delay.c | 8 +++++--- 3 files changed, 6 insertions(+), 7 deletions(-)