5 files changed, 162 insertions, 19 deletions

diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig
index 44ee7f6acf7b..82cb2a3f127a 100644
--- a/arch/x86_64/Kconfig
+++ b/arch/x86_64/Kconfig
@@ -303,6 +303,20 @@ config HPET_TIMER
           as it is off-chip.  You can find the HPET spec at
           <http://www.intel.com/labs/platcomp/hpet/hpetspec.htm>.
 
+config X86_PM_TIMER
+        bool "PM timer"
+        default y
+        help
+          Support the ACPI PM timer for time keeping. This is slow,
+          but is useful on some chipsets without HPET on systems with more
+          than one CPU. On a single processor or single socket multi core
+          system it is normally not required.
+          When the PM timer is active 64bit vsyscalls are disabled
+          and should not be enabled (/proc/sys/kernel/vsyscall64 should
+          not be changed).
+          The kernel selects the PM timer only as a last resort, so it is
+          useful to enable just in case.
+
 config HPET_EMULATE_RTC
         bool "Provide RTC interrupt"
         depends on HPET_TIMER && RTC=y
diff --git a/arch/x86_64/kernel/Makefile b/arch/x86_64/kernel/Makefile
index 0a3318e08ab6..5ca4a4598fda 100644
--- a/arch/x86_64/kernel/Makefile
+++ b/arch/x86_64/kernel/Makefile
@@ -28,6 +28,7 @@ obj-$(CONFIG_GART_IOMMU)	+= pci-gart.o aperture.o
 obj-$(CONFIG_DUMMY_IOMMU)       += pci-nommu.o pci-dma.o
 obj-$(CONFIG_SWIOTLB)           += swiotlb.o
 obj-$(CONFIG_KPROBES)           += kprobes.o
+obj-$(CONFIG_X86_PM_TIMER)      += pmtimer.o
 
 obj-$(CONFIG_MODULES)           += module.o
 
diff --git a/arch/x86_64/kernel/pmtimer.c b/arch/x86_64/kernel/pmtimer.c
new file mode 100644
index 000000000000..feb5f108dd26
--- /dev/null
+++ b/arch/x86_64/kernel/pmtimer.c
@@ -0,0 +1,101 @@
+/* Ported over from i386 by AK, original copyright was:
+ *
+ * (C) Dominik Brodowski <linux@brodo.de> 2003
+ *
+ * Driver to use the Power Management Timer (PMTMR) available in some
+ * southbridges as primary timing source for the Linux kernel.
+ *
+ * Based on parts of linux/drivers/acpi/hardware/hwtimer.c, timer_pit.c,
+ * timer_hpet.c, and on Arjan van de Ven's implementation for 2.4.
+ *
+ * This file is licensed under the GPL v2.
+ *
+ * Dropped all the hardware bug workarounds for now. Hopefully they
+ * are not needed on 64bit chipsets.
+ */
+
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/time.h>
+#include <linux/init.h>
+#include <linux/cpumask.h>
+#include <asm/io.h>
+#include <asm/proto.h>
+#include <asm/msr.h>
+#include <asm/vsyscall.h>
+
+/* The I/O port the PMTMR resides at.
+ * The location is detected during setup_arch(),
+ * in arch/i386/kernel/acpi/boot.c */
+u32 pmtmr_ioport;
+
+/* value of the Power timer at last timer interrupt */
+static u32 offset_delay;
+static u32 last_pmtmr_tick;
+
+#define ACPI_PM_MASK 0xFFFFFF /* limit it to 24 bits */
+
+static inline u32 cyc2us(u32 cycles)
+{
+        /* The Power Management Timer ticks at 3.579545 ticks per microsecond.
+         * 1 / PM_TIMER_FREQUENCY == 0.27936511 =~ 286/1024 [error: 0.024%]
+         *
+         * Even with HZ = 100, delta is at maximum 35796 ticks, so it can
+         * easily be multiplied with 286 (=0x11E) without having to fear
+         * u32 overflows.
+         */
+        cycles *= 286;
+        return (cycles >> 10);
+}
+
+int pmtimer_mark_offset(void)
+{
+        static int first_run = 1;
+        unsigned long tsc;
+        u32 lost;
+
+        u32 tick = inl(pmtmr_ioport);
+        u32 delta;
+
+        delta = cyc2us((tick - last_pmtmr_tick) & ACPI_PM_MASK);
+
+        last_pmtmr_tick = tick;
+        monotonic_base += delta * NSEC_PER_USEC;
+
+        delta += offset_delay;
+
+        lost = delta / (USEC_PER_SEC / HZ);
+        offset_delay = delta % (USEC_PER_SEC / HZ);
+
+        rdtscll(tsc);
+        vxtime.last_tsc = tsc - offset_delay * cpu_khz;
+
+        /* don't calculate delay for first run,
+           or if we've got less then a tick */
+        if (first_run || (lost < 1)) {
+                first_run = 0;
+                offset_delay = 0;
+        }
+
+        return lost - 1;
+}
+
+unsigned int do_gettimeoffset_pm(void)
+{
+        u32 now, offset, delta = 0;
+
+        offset = last_pmtmr_tick;
+        now = inl(pmtmr_ioport);
+        delta = (now - offset) & ACPI_PM_MASK;
+
+        return offset_delay + cyc2us(delta);
+}
+
+
+static int __init nopmtimer_setup(char *s)
+{
+        pmtmr_ioport = 0;
+        return 0;
+}
+
+__setup("nopmtimer", nopmtimer_setup);
diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
index 0e3b60e1ac5b..735b6767c8ed 100644
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -26,6 +26,8 @@
 #include <linux/sysdev.h>
 #include <linux/bcd.h>
 #include <linux/kallsyms.h>
+#include <linux/acpi.h>
+#include <acpi/achware.h>       /* for PM timer frequency */
 #include <asm/8253pit.h>
 #include <asm/pgtable.h>
 #include <asm/vsyscall.h>
@@ -396,6 +398,10 @@ static irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
                         (offset - vxtime.last)*(NSEC_PER_SEC/HZ) / hpet_tick;
 
                 vxtime.last = offset;
+#ifdef CONFIG_X86_PM_TIMER
+        } else if (vxtime.mode == VXTIME_PMTMR) {
+                lost = pmtimer_mark_offset();
+#endif
         } else {
                 offset = (((tsc - vxtime.last_tsc) *
                            vxtime.tsc_quot) >> 32) - (USEC_PER_SEC / HZ);
@@ -898,6 +904,13 @@ void __init time_init(void)
                         hpet_period;
                 cpu_khz = hpet_calibrate_tsc();
                 timename = "HPET";
+#ifdef CONFIG_X86_PM_TIMER
+        } else if (pmtmr_ioport) {
+                vxtime_hz = PM_TIMER_FREQUENCY;
+                timename = "PM";
+                pit_init();
+                cpu_khz = pit_calibrate_tsc();
+#endif
         } else {
                 pit_init();
                 cpu_khz = pit_calibrate_tsc();
@@ -923,35 +936,50 @@ void __init time_init(void)
 }
 
 /*
+ * Make an educated guess if the TSC is trustworthy and synchronized
+ * over all CPUs.
+ */
+static __init int unsynchronized_tsc(void)
+{
+#ifdef CONFIG_SMP
+        if (oem_force_hpet_timer())
+                return 1;
+        /* Intel systems are normally all synchronized. Exceptions
+           are handled in the OEM check above. */
+        if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
+                return 0;
+        /* All in a single socket - should be synchronized */
+        if (cpus_weight(cpu_core_map[0]) == num_online_cpus())
+                return 0;
+#endif
+        /* Assume multi socket systems are not synchronized */
+        return num_online_cpus() > 1;
+}
+
+/*
  * Decide after all CPUs are booted what mode gettimeofday should use.
  */
 void __init time_init_gtod(void)
 {
         char *timetype;
 
-        /*
-         * AMD systems with more than one CPU don't have fully synchronized
-         * TSCs. Always use HPET gettimeofday for these, although it is slower.
-         * Intel SMP systems usually have synchronized TSCs, so use always
-         * the TSC.
-         *
-         * Exceptions:
-         * IBM Summit2 checked by oem_force_hpet_timer().
-         * AMD dual core may also not need HPET. Check me.
-         *
-         * Can be turned off with "notsc".
-         */
-        if (num_online_cpus() > 1 &&
-            boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
-                notsc = 1;
-        /* Some systems will want to disable TSC and use HPET. */
-        if (oem_force_hpet_timer())
+        if (unsynchronized_tsc())
                 notsc = 1;
         if (vxtime.hpet_address && notsc) {
                 timetype = "HPET";
                 vxtime.last = hpet_readl(HPET_T0_CMP) - hpet_tick;
                 vxtime.mode = VXTIME_HPET;
                 do_gettimeoffset = do_gettimeoffset_hpet;
+#ifdef CONFIG_X86_PM_TIMER
+        /* Using PM for gettimeofday is quite slow, but we have no other
+           choice because the TSC is too unreliable on some systems. */
+        } else if (pmtmr_ioport && !vxtime.hpet_address && notsc) {
+                timetype = "PM";
+                do_gettimeoffset = do_gettimeoffset_pm;
+                vxtime.mode = VXTIME_PMTMR;
+                sysctl_vsyscall = 0;
+                printk(KERN_INFO "Disabling vsyscall due to use of PM timer\n");
+#endif
         } else {
                 timetype = vxtime.hpet_address ? "HPET/TSC" : "PIT/TSC";
                 vxtime.mode = VXTIME_TSC;
diff --git a/arch/x86_64/kernel/vsyscall.c b/arch/x86_64/kernel/vsyscall.c
index b4b8dc59663a..1a7541435ef0 100644
--- a/arch/x86_64/kernel/vsyscall.c
+++ b/arch/x86_64/kernel/vsyscall.c
@@ -65,7 +65,7 @@ static force_inline void do_vgettimeofday(struct timeval * tv)
                 usec = (__xtime.tv_nsec / 1000) +
                         (__jiffies - __wall_jiffies) * (1000000 / HZ);
 
-                if (__vxtime.mode == VXTIME_TSC) {
+                if (__vxtime.mode != VXTIME_HPET) {
                         sync_core();
                         rdtscll(t);
                         if (t < __vxtime.last_tsc)
@@ -217,7 +217,6 @@ static int __init vsyscall_init(void)
         BUG_ON((unsigned long) &vtime != VSYSCALL_ADDR(__NR_vtime));
         BUG_ON((VSYSCALL_ADDR(0) != __fix_to_virt(VSYSCALL_FIRST_PAGE)));
         map_vsyscall();
-        sysctl_vsyscall = 1;
         register_sysctl_table(kernel_root_table2, 0);
         return 0;
 }