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Message-Id: <1159826617.27968.22.camel@localhost.localdomain>
Date: Mon, 02 Oct 2006 15:03:37 -0700
From: john stultz <johnstul@...ibm.com>
To: Andrew Morton <akpm@...l.org>
Cc: Thomas Gleixner <tglx@...utronix.de>,
LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
Jim Gettys <jg@...top.org>,
David Woodhouse <dwmw2@...radead.org>,
Arjan van de Ven <arjan@...radead.org>,
Dave Jones <davej@...hat.com>
Subject: Re: [patch 03/23] GTOD: persistent clock support, i386
On Sat, 2006-09-30 at 01:36 -0700, Andrew Morton wrote:
> On Fri, 29 Sep 2006 23:58:22 -0000
> Thomas Gleixner <tglx@...utronix.de> wrote:
>
> > persistent clock support: do proper timekeeping across suspend/resume,
> > i386 arch support.
> >
>
> This description implies that the patch implements something for i386
> > arch/i386/kernel/apm.c | 44 ---------------------------------------
> > arch/i386/kernel/time.c | 54 +---------------------------------------------
>
> but all it does is delete stuff.
Improved description included.
> I _assume_ that it switches i386 over to using the (undescribed) generic
> core, and it does that merely by implementing read_persistent_clock().
>
> But I'd have expected to see some Kconfig change in there as well?
Since there is a generic weak read_persistent_clock function, all that
is needed is for an arch to implement the read_persistent_clock function
and remove its arch specific suspend/resume code.
> Does this implementation support all forms of persistent clock which are
> known to exist on i386 platforms?
Yep. It converts the read_cmos_clock() function, which covers legacy
CMOS and EFI clocks.
> If/when you issue new changelogs, please describe what has to be done to
> port other architectures over to use this overall framework.
Included below.
> Do ports for other architectures exist?
I made a quick attempt earlier and covered most of the arches. However,
I'm sort of wrapping this up w/ the generic time conversion (it was one
of the changes I dropped in the GTOD rework earlier this year). I was
going to re-add this later, but then Thomas started seeing resume
ordering issues w/ the dynticks patch, so I raised the patches again.
Updated patch below:
thanks
-john
Convert i386's read_cmos_clock to the read_persistent_clock interface
and remove the arch specific suspend/resume code, as the generic
timekeeping code will now handle it.
If you wish to convert your arch to the read_persistent_clock code:
1) Implement read_persistent_clock in your arch.
2) Kill off xtime and jiffies modification in arch specific
initialization and suspend/resume.
Signed-off-by: John Stultz <johnstul@...ibm.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
Signed-off-by: John Stultz <johnstul@...ibm.com>
--
apm.c | 43 -------------------------------------------
time.c | 55 ++-----------------------------------------------------
2 files changed, 2 insertions(+), 96 deletions(-)
linux-2.6.18_timeofday-persistent-clock-i386_C7.patch
============================================
diff --git a/arch/i386/kernel/apm.c b/arch/i386/kernel/apm.c
index b42f2d9..e40e7ef 100644
--- a/arch/i386/kernel/apm.c
+++ b/arch/i386/kernel/apm.c
@@ -1153,28 +1153,6 @@ out:
spin_unlock(&user_list_lock);
}
-static void set_time(void)
-{
- struct timespec ts;
- if (got_clock_diff) { /* Must know time zone in order to set clock */
- ts.tv_sec = get_cmos_time() + clock_cmos_diff;
- ts.tv_nsec = 0;
- do_settimeofday(&ts);
- }
-}
-
-static void get_time_diff(void)
-{
-#ifndef CONFIG_APM_RTC_IS_GMT
- /*
- * Estimate time zone so that set_time can update the clock
- */
- clock_cmos_diff = -get_cmos_time();
- clock_cmos_diff += get_seconds();
- got_clock_diff = 1;
-#endif
-}
-
static void reinit_timer(void)
{
#ifdef INIT_TIMER_AFTER_SUSPEND
@@ -1214,19 +1192,6 @@ static int suspend(int vetoable)
local_irq_disable();
device_power_down(PMSG_SUSPEND);
- /* serialize with the timer interrupt */
- write_seqlock(&xtime_lock);
-
- /* protect against access to timer chip registers */
- spin_lock(&i8253_lock);
-
- get_time_diff();
- /*
- * Irq spinlock must be dropped around set_system_power_state.
- * We'll undo any timer changes due to interrupts below.
- */
- spin_unlock(&i8253_lock);
- write_sequnlock(&xtime_lock);
local_irq_enable();
save_processor_state();
@@ -1235,7 +1200,6 @@ static int suspend(int vetoable)
restore_processor_state();
local_irq_disable();
- set_time();
reinit_timer();
if (err == APM_NO_ERROR)
@@ -1265,11 +1229,6 @@ static void standby(void)
local_irq_disable();
device_power_down(PMSG_SUSPEND);
- /* serialize with the timer interrupt */
- write_seqlock(&xtime_lock);
- /* If needed, notify drivers here */
- get_time_diff();
- write_sequnlock(&xtime_lock);
local_irq_enable();
err = set_system_power_state(APM_STATE_STANDBY);
@@ -1363,7 +1322,6 @@ static void check_events(void)
ignore_bounce = 1;
if ((event != APM_NORMAL_RESUME)
|| (ignore_normal_resume == 0)) {
- set_time();
device_resume();
pm_send_all(PM_RESUME, (void *)0);
queue_event(event, NULL);
@@ -1379,7 +1337,6 @@ static void check_events(void)
break;
case APM_UPDATE_TIME:
- set_time();
break;
case APM_CRITICAL_SUSPEND:
diff --git a/arch/i386/kernel/time.c b/arch/i386/kernel/time.c
index 58a2d55..e43fe9a 100644
--- a/arch/i386/kernel/time.c
+++ b/arch/i386/kernel/time.c
@@ -216,7 +216,7 @@ irqreturn_t timer_interrupt(int irq, voi
}
/* not static: needed by APM */
-unsigned long get_cmos_time(void)
+unsigned long read_persistent_clock(void)
{
unsigned long retval;
unsigned long flags;
@@ -232,7 +232,7 @@ unsigned long get_cmos_time(void)
return retval;
}
-EXPORT_SYMBOL(get_cmos_time);
+EXPORT_SYMBOL(read_persistent_clock);
static void sync_cmos_clock(unsigned long dummy);
@@ -283,58 +283,19 @@ void notify_arch_cmos_timer(void)
mod_timer(&sync_cmos_timer, jiffies + 1);
}
-static long clock_cmos_diff;
-static unsigned long sleep_start;
-
-static int timer_suspend(struct sys_device *dev, pm_message_t state)
-{
- /*
- * Estimate time zone so that set_time can update the clock
- */
- unsigned long ctime = get_cmos_time();
-
- clock_cmos_diff = -ctime;
- clock_cmos_diff += get_seconds();
- sleep_start = ctime;
- return 0;
-}
-
static int timer_resume(struct sys_device *dev)
{
- unsigned long flags;
- unsigned long sec;
- unsigned long ctime = get_cmos_time();
- long sleep_length = (ctime - sleep_start) * HZ;
- struct timespec ts;
-
- if (sleep_length < 0) {
- printk(KERN_WARNING "CMOS clock skew detected in timer resume!\n");
- /* The time after the resume must not be earlier than the time
- * before the suspend or some nasty things will happen
- */
- sleep_length = 0;
- ctime = sleep_start;
- }
#ifdef CONFIG_HPET_TIMER
if (is_hpet_enabled())
hpet_reenable();
#endif
setup_pit_timer();
-
- sec = ctime + clock_cmos_diff;
- ts.tv_sec = sec;
- ts.tv_nsec = 0;
- do_settimeofday(&ts);
- write_seqlock_irqsave(&xtime_lock, flags);
- jiffies_64 += sleep_length;
- write_sequnlock_irqrestore(&xtime_lock, flags);
touch_softlockup_watchdog();
return 0;
}
static struct sysdev_class timer_sysclass = {
.resume = timer_resume,
- .suspend = timer_suspend,
set_kset_name("timer"),
};
@@ -360,12 +321,6 @@ extern void (*late_time_init)(void);
/* Duplicate of time_init() below, with hpet_enable part added */
static void __init hpet_time_init(void)
{
- struct timespec ts;
- ts.tv_sec = get_cmos_time();
- ts.tv_nsec = (INITIAL_JIFFIES % HZ) * (NSEC_PER_SEC / HZ);
-
- do_settimeofday(&ts);
-
if ((hpet_enable() >= 0) && hpet_use_timer) {
printk("Using HPET for base-timer\n");
}
@@ -376,7 +331,6 @@ static void __init hpet_time_init(void)
void __init time_init(void)
{
- struct timespec ts;
#ifdef CONFIG_HPET_TIMER
if (is_hpet_capable()) {
/*
@@ -387,10 +341,5 @@ void __init time_init(void)
return;
}
#endif
- ts.tv_sec = get_cmos_time();
- ts.tv_nsec = (INITIAL_JIFFIES % HZ) * (NSEC_PER_SEC / HZ);
-
- do_settimeofday(&ts);
-
time_init_hook();
}
-
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