[IA64] Fix CONFIG_PRINTK_TIME

There were two problems with enabling the PRINTK_TIME config
option:
1) The first calls to printk() occur before per-cpu data virtual
address is pinned into the TLB, so sched_clock() can fault.
2) sched_clock() is based on ar.itc, which may not be synchronized
across cpus.

Ken Chen started this patch, Tony Luck tinkered with it, and Jes
Sorensen perfected it.

Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c
index 028a2b95936c..a094ec49ccfa 100644
--- a/arch/ia64/kernel/time.c
+++ b/arch/ia64/kernel/time.c
@@ -278,3 +278,30 @@ udelay (unsigned long usecs)
         }
 }
 EXPORT_SYMBOL(udelay);
+
+static unsigned long long ia64_itc_printk_clock(void)
+{
+        if (ia64_get_kr(IA64_KR_PER_CPU_DATA))
+                return sched_clock();
+        return 0;
+}
+
+static unsigned long long ia64_default_printk_clock(void)
+{
+        return (unsigned long long)(jiffies_64 - INITIAL_JIFFIES) *
+                (1000000000/HZ);
+}
+
+unsigned long long (*ia64_printk_clock)(void) = &ia64_default_printk_clock;
+
+unsigned long long printk_clock(void)
+{
+        return ia64_printk_clock();
+}
+
+void __init
+ia64_setup_printk_clock(void)
+{
+        if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT))
+                ia64_printk_clock = ia64_itc_printk_clock;
+}