4 files changed, 53 insertions, 6 deletions

diff --git a/Documentation/x86_64/boot-options.txt b/Documentation/x86_64/boot-options.txt
index 654ea4fccff8..153740f460a6 100644
--- a/Documentation/x86_64/boot-options.txt
+++ b/Documentation/x86_64/boot-options.txt
@@ -47,6 +47,11 @@ APICs
    noapicmaintimer  Don't do time keeping using the APIC timer.
                  Useful when this option was auto selected, but doesn't work.
 
+   apicpmtimer
+                 Do APIC timer calibration using the pmtimer. Implies
+                 apicmaintimer. Useful when your PIT timer is totally
+                 broken.
+
 Early Console
 
    syntax: earlyprintk=vga
diff --git a/arch/x86_64/kernel/apic.c b/arch/x86_64/kernel/apic.c
index 673a2fe9923c..c02218b3ae2b 100644
--- a/arch/x86_64/kernel/apic.c
+++ b/arch/x86_64/kernel/apic.c
@@ -40,6 +40,7 @@
 
 int apic_verbosity;
 int apic_runs_main_timer;
+int apic_calibrate_pmtmr __initdata;
 
 int disable_apic_timer __initdata;
 
@@ -746,14 +747,27 @@ static int __init calibrate_APIC_clock(void)
         __setup_APIC_LVTT(1000000000);
 
         apic_start = apic_read(APIC_TMCCT);
-        rdtscl(tsc_start);
-
-        do {
+#ifdef CONFIG_X86_PM_TIMER
+        if (apic_calibrate_pmtmr && pmtmr_ioport) {
+                pmtimer_wait(5000);  /* 5ms wait */
                 apic = apic_read(APIC_TMCCT);
-                rdtscl(tsc);
-        } while ((tsc - tsc_start) < TICK_COUNT && (apic - apic_start) < TICK_COUNT);
+                result = (apic_start - apic) * 1000L / 5;
+        } else
+#endif
+        {
+                rdtscl(tsc_start);
+
+                do {
+                        apic = apic_read(APIC_TMCCT);
+                        rdtscl(tsc);
+                } while ((tsc - tsc_start) < TICK_COUNT &&
+                                (apic - apic_start) < TICK_COUNT);
+
+                result = (apic_start - apic) * 1000L * cpu_khz /
+                                        (tsc - tsc_start);
+        }
+        printk("result %d\n", result);
 
-        result = (apic_start - apic) * 1000L * cpu_khz / (tsc - tsc_start);
 
         printk(KERN_INFO "Detected %d.%03d MHz APIC timer.\n",
                 result / 1000 / 1000, result / 1000 % 1000);
@@ -1115,6 +1129,13 @@ static __init int setup_noapicmaintimer(char *str)
 }
 __setup("noapicmaintimer", setup_noapicmaintimer);
 
+static __init int setup_apicpmtimer(char *s)
+{
+        apic_calibrate_pmtmr = 1;
+        return setup_apicmaintimer(NULL);
+}
+__setup("apicpmtimer", setup_apicpmtimer);
+
 /* dummy parsing: see setup.c */
 
 __setup("disableapic", setup_disableapic); 
diff --git a/arch/x86_64/kernel/pmtimer.c b/arch/x86_64/kernel/pmtimer.c
index 8b2655ae4e61..5c51d10408a6 100644
--- a/arch/x86_64/kernel/pmtimer.c
+++ b/arch/x86_64/kernel/pmtimer.c
@@ -80,6 +80,26 @@ int pmtimer_mark_offset(void)
         return lost - 1;
 }
 
+static unsigned pmtimer_wait_tick(void)
+{
+        u32 a, b;
+        for (a = b = inl(pmtmr_ioport) & ACPI_PM_MASK;
+             a == b;
+             b = inl(pmtmr_ioport) & ACPI_PM_MASK)
+                ;
+        return b;
+}
+
+/* note: wait time is rounded up to one tick */
+void pmtimer_wait(unsigned us)
+{
+        u32 a, b;
+        a = pmtimer_wait_tick();
+        do {
+                b = inl(pmtmr_ioport);
+        } while (cyc2us(b - a) < us);
+}
+
 void pmtimer_resume(void)
 {
         last_pmtmr_tick = inl(pmtmr_ioport);
diff --git a/include/asm-x86_64/proto.h b/include/asm-x86_64/proto.h
index a6748b9568fe..c99832e7bf3f 100644
--- a/include/asm-x86_64/proto.h
+++ b/include/asm-x86_64/proto.h
@@ -42,6 +42,7 @@ extern void iommu_hole_init(void);
 extern void time_init_gtod(void);
 extern int pmtimer_mark_offset(void);
 extern void pmtimer_resume(void);
+extern void pmtimer_wait(unsigned);
 extern unsigned int do_gettimeoffset_pm(void);
 #ifdef CONFIG_X86_PM_TIMER
 extern u32 pmtmr_ioport;