[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>

3 files changed, 32 insertions, 0 deletions

diff --git a/arch/ia64/kernel/head.S b/arch/ia64/kernel/head.S
index fbc7ea35dd57..f1778a84ea61 100644
--- a/arch/ia64/kernel/head.S
+++ b/arch/ia64/kernel/head.S
@@ -352,6 +352,7 @@ start_ap:
         mov ar.rsc=0            // place RSE in enforced lazy mode
         ;;
         loadrs                  // clear the dirty partition
+        mov IA64_KR(PER_CPU_DATA)=r0    // clear physical per-CPU base
         ;;
         mov ar.bspstore=r2      // establish the new RSE stack
         ;;
diff --git a/arch/ia64/kernel/setup.c b/arch/ia64/kernel/setup.c
index c0766575a3a2..35f7835294a3 100644
--- a/arch/ia64/kernel/setup.c
+++ b/arch/ia64/kernel/setup.c
@@ -71,6 +71,8 @@ unsigned long __per_cpu_offset[NR_CPUS];
 EXPORT_SYMBOL(__per_cpu_offset);
 #endif
 
+extern void ia64_setup_printk_clock(void);
+
 DEFINE_PER_CPU(struct cpuinfo_ia64, cpu_info);
 DEFINE_PER_CPU(unsigned long, local_per_cpu_offset);
 DEFINE_PER_CPU(unsigned long, ia64_phys_stacked_size_p8);
@@ -445,6 +447,8 @@ setup_arch (char **cmdline_p)
         /* process SAL system table: */
         ia64_sal_init(efi.sal_systab);
 
+        ia64_setup_printk_clock();
+
 #ifdef CONFIG_SMP
         cpu_physical_id(0) = hard_smp_processor_id();
 
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;
+}