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
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
--- /dev/null
+/* 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);
#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>
(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);
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();
#endif
}
+/*
+ * 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.
*/
{
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;
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)
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;
}
extern void iommu_hole_init(void);
extern void time_init_gtod(void);
+extern int pmtimer_mark_offset(void);
+extern unsigned int do_gettimeoffset_pm(void);
+extern u32 pmtmr_ioport;
+extern unsigned long long monotonic_base;
+extern int sysctl_vsyscall;
extern void do_softirq_thunk(void);
#define VXTIME_TSC 1
#define VXTIME_HPET 2
+#define VXTIME_PMTMR 3
struct vxtime_data {
long hpet_address; /* HPET base address */
extern int sysctl_vsyscall;
extern seqlock_t xtime_lock;
+extern int sysctl_vsyscall;
+
#define ARCH_HAVE_XTIME_LOCK 1
#endif /* __KERNEL__ */
projects / linux-2.6 / commitdiff