[PATCH] Disable sync of RTC during boot 2.6.10-rc1
From: Richard Griffiths
Date: Fri Oct 29 2004 - 17:19:38 EST
The get_cmos_time routine syncs during the read of the Real Time Clock by
doing a busy loop, this can take up to a full second. By passing an
argument to get_cmos_time, the sync can be skipped, thus speeding up the
kernel boot. All other calls to get_cmos_time enable the sync unless
multiple calls are made from within the same function such as
time_suspend(), time_resume().
The patch modifies get_cmos_time() for all architectures, but I've only
tested it on i386.
Richard
Signed-off-by: Richard Griffiths <richardx.a.griffiths@xxxxxxxxx>
# arch/cris/kernel/crisksyms.c | 2 +-
# arch/cris/kernel/time.c | 5 +++--
# arch/i386/kernel/apm.c | 8 +++++---
# arch/i386/kernel/i386_ksyms.c | 2 +-
# arch/i386/kernel/time.c | 20 ++++++++++++--------
# arch/sh/boards/mpc1211/rtc.c | 20 +++++++++++---------
# arch/x86_64/kernel/time.c | 21 +++++++++++++--------
# arch/x86_64/kernel/x8664_ksyms.c | 2 +-
# include/asm-i386/mach-default/mach_time.h | 18 ++++++++++--------
# 9 files changed, 57 insertions(+), 41 deletions(-)
#
# This is a BitKeeper generated diff -Nru style patch.
#
# ChangeSet
# 2004/10/29 13:51:27-07:00 richardg@xxxxxxxxxxxxxxxxxxx
# get_cmos_time attempt to sync with the RTC by looping for up to 1 second to
# to catch the UIP flag changing. By passing an argument to disable the
# sync when called from time_init during boot, the time to read the RTC is cut
# to a few microseconds. The sync is enabled for most other calls to
# get_cmos_time. The code has been done for all architectures, but has only
# been tested on i386.
#
# include/asm-i386/mach-default/mach_time.h
# 2004/10/29 13:51:14-07:00 richardg@xxxxxxxxxxxxxxxxxxx +10 -8
# added an arg to cmos_get_time routines to enable or disable the sync which
# can take up to one second. Disabled during boot - enabled for most calls.
#
# arch/x86_64/kernel/x8664_ksyms.c
# 2004/10/29 13:51:14-07:00 richardg@xxxxxxxxxxxxxxxxxxx +1 -1
# added an arg to cmos_get_time routines to enable or disable the sync which
# can take up to one second. Disabled during boot - enabled for most calls.
#
# arch/x86_64/kernel/time.c
# 2004/10/29 13:51:14-07:00 richardg@xxxxxxxxxxxxxxxxxxx +13 -8
# added an arg to cmos_get_time routines to enable or disable the sync which
# can take up to one second. Disabled during boot - enabled for most calls.
#
# arch/sh/boards/mpc1211/rtc.c
# 2004/10/29 13:51:14-07:00 richardg@xxxxxxxxxxxxxxxxxxx +11 -9
# added an arg to cmos_get_time routines to enable or disable the sync which
# can take up to one second. Disabled during boot - enabled for most calls.
#
# arch/i386/kernel/time.c
# 2004/10/29 13:51:14-07:00 richardg@xxxxxxxxxxxxxxxxxxx +12 -8
# added an arg to cmos_get_time routines to enable or disable the sync which
# can take up to one second. Disabled during boot - enabled for most calls.
#
# arch/i386/kernel/i386_ksyms.c
# 2004/10/29 13:51:14-07:00 richardg@xxxxxxxxxxxxxxxxxxx +1 -1
# added an arg to cmos_get_time routines to enable or disable the sync which
# can take up to one second. Disabled during boot - enabled for most calls.
#
# BitKeeper/etc/ignore
# 2004/10/29 13:51:14-07:00 richardg@xxxxxxxxxxxxxxxxxxx +2 -0
# Added rtcnosync-2.6.10-rc1.patch rtcnosync.patch to the ignore list
#
# arch/i386/kernel/apm.c
# 2004/10/29 13:51:13-07:00 richardg@xxxxxxxxxxxxxxxxxxx +5 -3
# added an arg to cmos_get_time routines to enable or disable the sync which
# can take up to one second. Disabled during boot - enabled for most calls.
#
# arch/cris/kernel/time.c
# 2004/10/29 13:51:13-07:00 richardg@xxxxxxxxxxxxxxxxxxx +3 -2
# added an arg to cmos_get_time routines to enable or disable the sync which
# can take up to one second. Disabled during boot - enabled for most calls.
#
# arch/cris/kernel/crisksyms.c
# 2004/10/29 13:51:13-07:00 richardg@xxxxxxxxxxxxxxxxxxx +1 -1
# added an arg to cmos_get_time routines to enable or disable the sync which
# can take up to one second. Disabled during boot - enabled for most calls.
#
diff -Nru a/arch/cris/kernel/crisksyms.c b/arch/cris/kernel/crisksyms.c
--- a/arch/cris/kernel/crisksyms.c 2004-10-29 13:52:40 -07:00
+++ b/arch/cris/kernel/crisksyms.c 2004-10-29 13:52:40 -07:00
@@ -22,7 +22,7 @@
#include <asm/fasttimer.h>
extern void dump_thread(struct pt_regs *, struct user *);
-extern unsigned long get_cmos_time(void);
+extern unsigned long get_cmos_time(int);
extern void __Udiv(void);
extern void __Umod(void);
extern void __Div(void);
diff -Nru a/arch/cris/kernel/time.c b/arch/cris/kernel/time.c
--- a/arch/cris/kernel/time.c 2004-10-29 13:52:40 -07:00
+++ b/arch/cris/kernel/time.c 2004-10-29 13:52:40 -07:00
@@ -173,7 +173,7 @@
/* grab the time from the RTC chip */
unsigned long
-get_cmos_time(void)
+get_cmos_time(sync_read)
{
unsigned int year, mon, day, hour, min, sec;
@@ -208,8 +208,9 @@
void
update_xtime_from_cmos(void)
{
+ int sync_read = 0; /* unused */
if(have_rtc) {
- xtime.tv_sec = get_cmos_time();
+ xtime.tv_sec = get_cmos_time(sync_read);
xtime.tv_nsec = 0;
}
}
diff -Nru a/arch/i386/kernel/apm.c b/arch/i386/kernel/apm.c
--- a/arch/i386/kernel/apm.c 2004-10-29 13:52:40 -07:00
+++ b/arch/i386/kernel/apm.c 2004-10-29 13:52:40 -07:00
@@ -232,7 +232,7 @@
#include "io_ports.h"
extern spinlock_t i8253_lock;
-extern unsigned long get_cmos_time(void);
+extern unsigned long get_cmos_time(int);
extern void machine_real_restart(unsigned char *, int);
#if defined(CONFIG_APM_DISPLAY_BLANK) && defined(CONFIG_VT)
@@ -1147,8 +1147,9 @@
static void set_time(void)
{
+ int sync_read = 1;
if (got_clock_diff) { /* Must know time zone in order to set clock */
- xtime.tv_sec = get_cmos_time() + clock_cmos_diff;
+ xtime.tv_sec = get_cmos_time(sync_read) + clock_cmos_diff;
xtime.tv_nsec = 0;
}
}
@@ -1156,10 +1157,11 @@
static void get_time_diff(void)
{
#ifndef CONFIG_APM_RTC_IS_GMT
+ int sync_read = 1;
/*
* Estimate time zone so that set_time can update the clock
*/
- clock_cmos_diff = -get_cmos_time();
+ clock_cmos_diff = -get_cmos_time(sync_read);
clock_cmos_diff += get_seconds();
got_clock_diff = 1;
#endif
diff -Nru a/arch/i386/kernel/i386_ksyms.c b/arch/i386/kernel/i386_ksyms.c
--- a/arch/i386/kernel/i386_ksyms.c 2004-10-29 13:52:40 -07:00
+++ b/arch/i386/kernel/i386_ksyms.c 2004-10-29 13:52:40 -07:00
@@ -57,7 +57,7 @@
#endif
extern unsigned long cpu_khz;
-extern unsigned long get_cmos_time(void);
+extern unsigned long get_cmos_time(int);
/* platform dependent support */
EXPORT_SYMBOL(boot_cpu_data);
diff -Nru a/arch/i386/kernel/time.c b/arch/i386/kernel/time.c
--- a/arch/i386/kernel/time.c 2004-10-29 13:52:40 -07:00
+++ b/arch/i386/kernel/time.c 2004-10-29 13:52:40 -07:00
@@ -303,7 +303,7 @@
}
/* not static: needed by APM */
-unsigned long get_cmos_time(void)
+unsigned long get_cmos_time(int sync_read)
{
unsigned long retval;
@@ -312,7 +312,7 @@
if (efi_enabled)
retval = efi_get_time();
else
- retval = mach_get_cmos_time();
+ retval = mach_get_cmos_time(sync_read);
spin_unlock(&rtc_lock);
@@ -323,20 +323,22 @@
static int time_suspend(struct sys_device *dev, u32 state)
{
+ int sync_read = 1;
/*
* Estimate time zone so that set_time can update the clock
*/
- clock_cmos_diff = -get_cmos_time();
+ clock_cmos_diff = -get_cmos_time(sync_read);
clock_cmos_diff += get_seconds();
- sleep_start = get_cmos_time();
+ sleep_start = get_cmos_time(sync_read = 0);
return 0;
}
static int time_resume(struct sys_device *dev)
{
+ int sync_read = 1;
unsigned long flags;
- unsigned long sec = get_cmos_time() + clock_cmos_diff;
- unsigned long sleep_length = get_cmos_time() - sleep_start;
+ unsigned long sec = get_cmos_time(sync_read) + clock_cmos_diff;
+ unsigned long sleep_length = get_cmos_time(sync_read = 0) - sleep_start;
write_seqlock_irqsave(&xtime_lock, flags);
xtime.tv_sec = sec;
@@ -374,7 +376,8 @@
/* Duplicate of time_init() below, with hpet_enable part added */
void __init hpet_time_init(void)
{
- xtime.tv_sec = get_cmos_time();
+ int sync_read = 0;
+ xtime.tv_sec = get_cmos_time(sync_read);
wall_to_monotonic.tv_sec = -xtime.tv_sec;
xtime.tv_nsec = (INITIAL_JIFFIES % HZ) * (NSEC_PER_SEC / HZ);
wall_to_monotonic.tv_nsec = -xtime.tv_nsec;
@@ -392,6 +395,7 @@
void __init time_init(void)
{
+ int sync_read = 0;
#ifdef CONFIG_HPET_TIMER
if (is_hpet_capable()) {
/*
@@ -402,7 +406,7 @@
return;
}
#endif
- xtime.tv_sec = get_cmos_time();
+ xtime.tv_sec = get_cmos_time(sync_read);
wall_to_monotonic.tv_sec = -xtime.tv_sec;
xtime.tv_nsec = (INITIAL_JIFFIES % HZ) * (NSEC_PER_SEC / HZ);
wall_to_monotonic.tv_nsec = -xtime.tv_nsec;
diff -Nru a/arch/sh/boards/mpc1211/rtc.c b/arch/sh/boards/mpc1211/rtc.c
--- a/arch/sh/boards/mpc1211/rtc.c 2004-10-29 13:52:40 -07:00
+++ b/arch/sh/boards/mpc1211/rtc.c 2004-10-29 13:52:40 -07:00
@@ -20,7 +20,7 @@
#endif
/* arc/i386/kernel/time.c */
-unsigned long get_cmos_time(void)
+unsigned long get_cmos_time(sync_read))
{
unsigned int year, mon, day, hour, min, sec;
int i;
@@ -32,12 +32,14 @@
* Let's hope other operating systems interpret the RTC the same way.
*/
/* read RTC exactly on falling edge of update flag */
- for (i = 0 ; i < 1000000 ; i++) /* may take up to 1 second... */
- if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP)
- break;
- for (i = 0 ; i < 1000000 ; i++) /* must try at least 2.228 ms */
- if (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
- break;
+ if(sync_read){
+ for (i = 0 ; i < 1000000 ; i++) /* may take up to 1 second... */
+ if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP)
+ break;
+ for (i = 0 ; i < 1000000 ; i++) /* must try at least 2.228 ms */
+ if (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
+ break;
+ }
do { /* Isn't this overkill ? UIP above should guarantee consistency */
sec = CMOS_READ(RTC_SECONDS);
min = CMOS_READ(RTC_MINUTES);
@@ -63,8 +65,8 @@
void mpc1211_rtc_gettimeofday(struct timeval *tv)
{
-
- tv->tv_sec = get_cmos_time();
+ int sync_read = 1;
+ tv->tv_sec = get_cmos_time(sync_read);
tv->tv_usec = 0;
}
diff -Nru a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
--- a/arch/x86_64/kernel/time.c 2004-10-29 13:52:40 -07:00
+++ b/arch/x86_64/kernel/time.c 2004-10-29 13:52:40 -07:00
@@ -499,7 +499,7 @@
return cycles_2_ns(a);
}
-unsigned long get_cmos_time(void)
+unsigned long get_cmos_time(sync_read))
{
unsigned int timeout, year, mon, day, hour, min, sec;
unsigned char last, this;
@@ -518,10 +518,12 @@
timeout = 1000000;
last = this = 0;
- while (timeout && last && !this) {
- last = this;
- this = CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP;
- timeout--;
+ if(sync_read){
+ while (timeout && last && !this) {
+ last = this;
+ this = CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP;
+ timeout--;
+ }
}
/*
@@ -858,6 +860,7 @@
void __init time_init(void)
{
char *timename;
+ int sync_read = 0;
#ifdef HPET_HACK_ENABLE_DANGEROUS
if (!vxtime.hpet_address) {
@@ -874,7 +877,7 @@
if (nohpet)
vxtime.hpet_address = 0;
- xtime.tv_sec = get_cmos_time();
+ xtime.tv_sec = get_cmos_time(sync_read);
xtime.tv_nsec = 0;
set_normalized_timespec(&wall_to_monotonic,
@@ -943,18 +946,20 @@
static int time_suspend(struct sys_device *dev, u32 state)
{
+ int sync_read = 1;
/*
* Estimate time zone so that set_time can update the clock
*/
- clock_cmos_diff = -get_cmos_time();
+ clock_cmos_diff = -get_cmos_time(sync_read);
clock_cmos_diff += get_seconds();
return 0;
}
static int time_resume(struct sys_device *dev)
{
+ int sync_read = 1;
unsigned long flags;
- unsigned long sec = get_cmos_time() + clock_cmos_diff;
+ unsigned long sec = get_cmos_time(sync_read) + clock_cmos_diff;
write_seqlock_irqsave(&xtime_lock,flags);
xtime.tv_sec = sec;
xtime.tv_nsec = 0;
diff -Nru a/arch/x86_64/kernel/x8664_ksyms.c b/arch/x86_64/kernel/x8664_ksyms.c
--- a/arch/x86_64/kernel/x8664_ksyms.c 2004-10-29 13:52:40 -07:00
+++ b/arch/x86_64/kernel/x8664_ksyms.c 2004-10-29 13:52:40 -07:00
@@ -45,7 +45,7 @@
EXPORT_SYMBOL(drive_info);
#endif
-extern unsigned long get_cmos_time(void);
+extern unsigned long get_cmos_time(int);
/* platform dependent support */
EXPORT_SYMBOL(boot_cpu_data);
diff -Nru a/include/asm-i386/mach-default/mach_time.h b/include/asm-i386/mach-default/mach_time.h
--- a/include/asm-i386/mach-default/mach_time.h 2004-10-29 13:52:40 -07:00
+++ b/include/asm-i386/mach-default/mach_time.h 2004-10-29 13:52:40 -07:00
@@ -79,7 +79,7 @@
return retval;
}
-static inline unsigned long mach_get_cmos_time(void)
+static inline unsigned long mach_get_cmos_time(int sync_read)
{
unsigned int year, mon, day, hour, min, sec;
int i;
@@ -89,13 +89,15 @@
* RTC registers show the second which has precisely just started.
* Let's hope other operating systems interpret the RTC the same way.
*/
- /* read RTC exactly on falling edge of update flag */
- for (i = 0 ; i < 1000000 ; i++) /* may take up to 1 second... */
- if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP)
- break;
- for (i = 0 ; i < 1000000 ; i++) /* must try at least 2.228 ms */
- if (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
- break;
+ if(sync_read) {
+ /* read RTC exactly on falling edge of update flag */
+ for (i = 0 ; i < 1000000 ; i++) /* may take up to 1 second... */
+ if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP)
+ break;
+ for (i = 0 ; i < 1000000 ; i++) /* must try at least 2.228 ms */
+ if (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
+ break;
+ }
do { /* Isn't this overkill ? UIP above should guarantee consistency */
sec = CMOS_READ(RTC_SECONDS);
min = CMOS_READ(RTC_MINUTES);
-
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