[PATCH/RFC] Modify sched_clock() to make CONFIG_PRINTK_TIME more sane.

[Tony Breeds]

When booting a current kernel with CONFIG_PRINTK_TIME enabled you'll
see messages like:

[    0.000000] time_init: decrementer frequency = 188.044000 MHz
[    0.000000] time_init: processor frequency   = 1504.352000 MHz
[3712914.436297] Console: colour dummy device 80x25

This patch modifies sched_clock() to report the offset since the machine booted
so the same printk's now look like:

[    0.000000] time_init: decrementer frequency = 188.044000 MHz
[    0.000000] time_init: processor frequency   = 1504.352000 MHz
[    0.000135] Console: colour dummy device 80x25

Effectivly including the uptime in printk()s.

Signed-off-by: Tony Breeds <tony at bakeyournoodle.com>

---

 arch/powerpc/kernel/time.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Index: working/arch/powerpc/kernel/time.c
===================================================================
--- working.orig/arch/powerpc/kernel/time.c
+++ working/arch/powerpc/kernel/time.c
@@ -115,6 +115,7 @@ EXPORT_SYMBOL_GPL(rtc_lock);
 
 u64 tb_to_ns_scale;
 unsigned tb_to_ns_shift;
+unsigned long boot_tb;
 
 struct gettimeofday_struct do_gtod;
 
@@ -735,7 +736,7 @@ unsigned long long sched_clock(void)
 {
 	if (__USE_RTC())
 		return get_rtc();
-	return mulhdu(get_tb(), tb_to_ns_scale) << tb_to_ns_shift;
+	return mulhdu(get_tb() - boot_tb, tb_to_ns_scale) << tb_to_ns_shift;
 }
 
 int do_settimeofday(struct timespec *tv)
@@ -960,6 +961,8 @@ void __init time_init(void)
 	}
 	tb_to_ns_scale = scale;
 	tb_to_ns_shift = shift;
+	/* Save the current timebase to pretty up CONFIG_PRINTK_TIME */
+	boot_tb = get_tb();
 
 	tm = get_boot_time();
 
Yours Tony

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