RE: [patch 012/100] acpi: fix of pmtimer overflow that make Cx states time incorrect

["Shi, Alex" <alex.shi@intel.com>]

It was reported make some latop booting hang. and is not root caused now. :(
http://bugzilla.kernel.org/show_bug.cgi?id=13087 

Alex 
>-----Original Message-----
>From: Chris Wright [mailto:chrisw@sous-sol.org]
>Sent: 2009年4月23日 15:21
>To: linux-kernel@vger.kernel.org; stable@kernel.org
>Cc: Justin Forbes; Zwane Mwaikambo; Theodore Ts'o; Randy Dunlap; Dave Jones;
>Chuck Wolber; Chris Wedgwood; Michael Krufky; Chuck Ebbert; Domenico Andreoli;
>Willy Tarreau; Rodrigo Rubira Branco; Jake Edge; Eugene Teo;
>torvalds@linux-foundation.org; akpm@linux-foundation.org;
>alan@lxorguk.ukuu.org.uk; Len Brown; linux-acpi@vger.kernel.org; Shi, Alex;
>Pallipadi, Venkatesh; Zhao, Yakui; Brown, Len
>Subject: [patch 012/100] acpi: fix of pmtimer overflow that make Cx states time
>incorrect
>
>-stable review patch.  If anyone has any objections, please let us know.
>---------------------
>
>From: alex.shi <alex.shi@intel.com>
>
>upstream commit: ff69f2bba67bd45514923aaedbf40fe351787c59
>
>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>
>Signed-off-by: Chris Wright <chrisw@sous-sol.org>
>---
> drivers/acpi/processor_idle.c |   63
>++++++++++++++++++------------------------
> 1 file changed, 27 insertions(+), 36 deletions(-)
>
>--- 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 __cpuinitdat
> 	{},
> };
>
>-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(st
> 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 cpu
> 		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
> {
> 	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
> 	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
>
> 	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 cpu
> {
> 	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 cpu
> 		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 cpu
> 	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 cpu
>
> 	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 = {