[PATCH 06/98] acpi: fix of pmtimer overflow that make Cx states time incorrect

Len Brown
2009-03-28T04:33:06Z

From: alex.shi <alex.shi@intel.com>

We found Cx states time abnormal in our some of machines which have 16
LCPUs, the C0 take too many time while system is really idle when kernel
enabled tickless and highres. powertop output is below:

PowerTOP version 1.9 (C) 2007 Intel Corporation

Cn Avg residency P-states (frequencies)
C0 (cpu running) (40.5%) 2.53 Ghz 0.0%
C1 0.0ms ( 0.0%) 2.53 Ghz 0.0%
C2 128.8ms (59.5%) 2.40 Ghz 0.0%
1.60 Ghz 100.0%

Wakeups-from-idle per second : 4.7 interval: 20.0s
no ACPI power usage estimate available

Top causes for wakeups:
41.4% ( 24.9) <interrupt> : extra timer interrupt
20.2% ( 12.2) <kernel core> : usb_hcd_poll_rh_status
(rh_timer_func)

After tacking detailed for this issue, Yakui and I find it is due to 24
bit PM timer overflows when some of cpu sleep more than 4 seconds. With
tickless kernel, the CPU want to sleep as much as possible when system
idle. But the Cx sleep time are recorded by pmtimer which length is
determined by BIOS. The current Cx time was gotten in the following
function from driver/acpi/processor_idle.c:

static inline u32 ticks_elapsed(u32 t1, u32 t2)
{
if (t2 >= t1)
return (t2 - t1);
else if (!(acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER))
return (((0x00FFFFFF - t1) + t2) & 0x00FFFFFF);
else
return ((0xFFFFFFFF - t1) + t2);
}

If pmtimer is 24 bits and it take 5 seconds from t1 to t2, in above
function, just about 1 seconds ticks was recorded. So the Cx time will be
reduced about 4 seconds. and this is why we see above powertop output.

To resolve this problem, Yakui and I use ktime_get() to record the Cx
states time instead of PM timer as the following patch. the patch was
tested with i386/x86_64 modes on several platforms.

Acked-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Tested-by: Alex Shi <alex.shi@intel.com>
Signed-off-by: Alex Shi <alex.shi@intel.com>
Signed-off-by: Yakui.zhao <yakui.zhao@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>
---
drivers/acpi/processor_idle.c | 63 +++++++++++++++++-----------------------
1 files changed, 27 insertions(+), 36 deletions(-)

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 7bc22a4..879af87 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -64,7 +64,6 @@
#define _COMPONENT ACPI_PROCESSOR_COMPONENT
ACPI_MODULE_NAME("processor_idle");
#define ACPI_PROCESSOR_FILE_POWER "power"
-#define US_TO_PM_TIMER_TICKS(t) ((t * (PM_TIMER_FREQUENCY/1000)) / 1000)
#define PM_TIMER_TICK_NS (1000000000ULL/PM_TIMER_FREQUENCY)
#define C2_OVERHEAD 1 /* 1us */
#define C3_OVERHEAD 1 /* 1us */
@@ -78,6 +77,10 @@ module_param(nocst, uint, 0000);
static unsigned int latency_factor __read_mostly = 2;
module_param(latency_factor, uint, 0644);

+static s64 us_to_pm_timer_ticks(s64 t)
+{
+ return div64_u64(t * PM_TIMER_FREQUENCY, 1000000);
+}
/*
* IBM ThinkPad R40e crashes mysteriously when going into C2 or C3.
* For now disable this. Probably a bug somewhere else.
@@ -159,25 +162,6 @@ static struct dmi_system_id __cpuinitdata processor_power_dmi_table[] = {
{},
};

-static inline u32 ticks_elapsed(u32 t1, u32 t2)
-{
- if (t2 >= t1)
- return (t2 - t1);
- else if (!(acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER))
- return (((0x00FFFFFF - t1) + t2) & 0x00FFFFFF);
- else
- return ((0xFFFFFFFF - t1) + t2);
-}
-
-static inline u32 ticks_elapsed_in_us(u32 t1, u32 t2)
-{
- if (t2 >= t1)
- return PM_TIMER_TICKS_TO_US(t2 - t1);
- else if (!(acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER))
- return PM_TIMER_TICKS_TO_US(((0x00FFFFFF - t1) + t2) & 0x00FFFFFF);
- else
- return PM_TIMER_TICKS_TO_US((0xFFFFFFFF - t1) + t2);
-}

/*
* Callers should disable interrupts before the call and enable
@@ -853,7 +837,8 @@ static inline void acpi_idle_do_entry(struct acpi_processor_cx *cx)
static int acpi_idle_enter_c1(struct cpuidle_device *dev,
struct cpuidle_state *state)
{
- u32 t1, t2;
+ ktime_t kt1, kt2;
+ s64 idle_time;
struct acpi_processor *pr;
struct acpi_processor_cx *cx = cpuidle_get_statedata(state);

@@ -871,14 +856,15 @@ static int acpi_idle_enter_c1(struct cpuidle_device *dev,
return 0;
}

- t1 = inl(acpi_gbl_FADT.xpm_timer_block.address);
+ kt1 = ktime_get_real();
acpi_idle_do_entry(cx);
- t2 = inl(acpi_gbl_FADT.xpm_timer_block.address);
+ kt2 = ktime_get_real();
+ idle_time = ktime_to_us(ktime_sub(kt2, kt1));

local_irq_enable();
cx->usage++;

- return ticks_elapsed_in_us(t1, t2);
+ return idle_time;
}

/**
@@ -891,8 +877,9 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
{
struct acpi_processor *pr;
struct acpi_processor_cx *cx = cpuidle_get_statedata(state);
- u32 t1, t2;
- int sleep_ticks = 0;
+ ktime_t kt1, kt2;
+ s64 idle_time;
+ s64 sleep_ticks = 0;

pr = __get_cpu_var(processors);

@@ -925,18 +912,19 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
if (cx->type == ACPI_STATE_C3)
ACPI_FLUSH_CPU_CACHE();

- t1 = inl(acpi_gbl_FADT.xpm_timer_block.address);
+ kt1 = ktime_get_real();
/* Tell the scheduler that we are going deep-idle: */
sched_clock_idle_sleep_event();
acpi_idle_do_entry(cx);
- t2 = inl(acpi_gbl_FADT.xpm_timer_block.address);
+ kt2 = ktime_get_real();
+ idle_time = ktime_to_us(ktime_sub(kt2, kt1));

#if defined (CONFIG_GENERIC_TIME) && defined (CONFIG_X86)
/* TSC could halt in idle, so notify users */
if (tsc_halts_in_c(cx->type))
mark_tsc_unstable("TSC halts in idle");;
#endif
- sleep_ticks = ticks_elapsed(t1, t2);
+ sleep_ticks = us_to_pm_timer_ticks(idle_time);

/* Tell the scheduler how much we idled: */
sched_clock_idle_wakeup_event(sleep_ticks*PM_TIMER_TICK_NS);
@@ -948,7 +936,7 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,

acpi_state_timer_broadcast(pr, cx, 0);
cx->time += sleep_ticks;
- return ticks_elapsed_in_us(t1, t2);
+ return idle_time;
}

static int c3_cpu_count;
@@ -966,8 +954,10 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
{
struct acpi_processor *pr;
struct acpi_processor_cx *cx = cpuidle_get_statedata(state);
- u32 t1, t2;
- int sleep_ticks = 0;
+ ktime_t kt1, kt2;
+ s64 idle_time;
+ s64 sleep_ticks = 0;
+

pr = __get_cpu_var(processors);

@@ -1034,9 +1024,10 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
ACPI_FLUSH_CPU_CACHE();
}

- t1 = inl(acpi_gbl_FADT.xpm_timer_block.address);
+ kt1 = ktime_get_real();
acpi_idle_do_entry(cx);
- t2 = inl(acpi_gbl_FADT.xpm_timer_block.address);
+ kt2 = ktime_get_real();
+ idle_time = ktime_to_us(ktime_sub(kt2, kt1));

/* Re-enable bus master arbitration */
if (pr->flags.bm_check && pr->flags.bm_control) {
@@ -1051,7 +1042,7 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
if (tsc_halts_in_c(ACPI_STATE_C3))
mark_tsc_unstable("TSC halts in idle");
#endif
- sleep_ticks = ticks_elapsed(t1, t2);
+ sleep_ticks = us_to_pm_timer_ticks(idle_time);
/* Tell the scheduler how much we idled: */
sched_clock_idle_wakeup_event(sleep_ticks*PM_TIMER_TICK_NS);

@@ -1062,7 +1053,7 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,

acpi_state_timer_broadcast(pr, cx, 0);
cx->time += sleep_ticks;
- return ticks_elapsed_in_us(t1, t2);
+ return idle_time;
}

struct cpuidle_driver acpi_idle_driver = {
--
1.6.0.6