[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, 13 deletions

diff --git a/arch/ia64/sn/kernel/setup.c b/arch/ia64/sn/kernel/setup.c
index ee36bff93c30..6ea5b8a37c01 100644
--- a/arch/ia64/sn/kernel/setup.c
+++ b/arch/ia64/sn/kernel/setup.c
@@ -67,6 +67,7 @@ extern unsigned long last_time_offset;
 extern void (*ia64_mark_idle) (int);
 extern void snidle(int);
 extern unsigned char acpi_kbd_controller_present;
+extern unsigned long long (*ia64_printk_clock)(void);
 
 unsigned long sn_rtc_cycles_per_second;
 EXPORT_SYMBOL(sn_rtc_cycles_per_second);
@@ -372,6 +373,16 @@ sn_scan_pcdp(void)
         }
 }
 
+static unsigned long sn2_rtc_initial;
+
+static unsigned long long ia64_sn2_printk_clock(void)
+{
+        unsigned long rtc_now = rtc_time();
+
+        return (rtc_now - sn2_rtc_initial) *
+                (1000000000 / sn_rtc_cycles_per_second);
+}
+
 /**
  * sn_setup - SN platform setup routine
  * @cmdline_p: kernel command line
@@ -386,6 +397,7 @@ void __init sn_setup(char **cmdline_p)
         u32 version = sn_sal_rev();
         extern void sn_cpu_init(void);
 
+        sn2_rtc_initial = rtc_time();
         ia64_sn_plat_set_error_handling_features();     // obsolete
         ia64_sn_set_os_feature(OSF_MCA_SLV_TO_OS_INIT_SLV);
         ia64_sn_set_os_feature(OSF_FEAT_LOG_SBES);
@@ -437,19 +449,6 @@ void __init sn_setup(char **cmdline_p)
          */
         build_cnode_tables();
 
-        /*
-         * Old PROMs do not provide an ACPI FADT. Disable legacy keyboard
-         * support here so we don't have to listen to failed keyboard probe
-         * messages.
-         */
-        if (version <= 0x0209 && acpi_kbd_controller_present) {
-                printk(KERN_INFO "Disabling legacy keyboard support as prom "
-                       "is too old and doesn't provide FADT\n");
-                acpi_kbd_controller_present = 0;
-        }
-
-        printk("SGI SAL version %x.%02x\n", version >> 8, version & 0x00FF);
-
         status =
             ia64_sal_freq_base(SAL_FREQ_BASE_REALTIME_CLOCK, &ticks_per_sec,
                                &drift);
@@ -463,6 +462,21 @@ void __init sn_setup(char **cmdline_p)
 
         platform_intr_list[ACPI_INTERRUPT_CPEI] = IA64_CPE_VECTOR;
 
+        ia64_printk_clock = ia64_sn2_printk_clock;
+
+        /*
+         * Old PROMs do not provide an ACPI FADT. Disable legacy keyboard
+         * support here so we don't have to listen to failed keyboard probe
+         * messages.
+         */
+        if (version <= 0x0209 && acpi_kbd_controller_present) {
+                printk(KERN_INFO "Disabling legacy keyboard support as prom "
+                       "is too old and doesn't provide FADT\n");
+                acpi_kbd_controller_present = 0;
+        }
+
+        printk("SGI SAL version %x.%02x\n", version >> 8, version & 0x00FF);
+
         /*
          * we set the default root device to /dev/hda
          * to make simulation easy