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authorAl Viro <viro@zeniv.linux.org.uk>2008-08-17 21:05:42 -0400
committerH. Peter Anvin <hpa@zytor.com>2008-10-22 22:55:20 -0700
commitbb8985586b7a906e116db835c64773b7a7d51663 (patch)
treede93ae58e88cc563d95cc124a73f3930594c6100 /arch/x86/include/asm/timer.h
parent8ede0bdb63305d3353efd97e9af6210afb05734e (diff)
x86, um: ... and asm-x86 move
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'arch/x86/include/asm/timer.h')
-rw-r--r--arch/x86/include/asm/timer.h66
1 files changed, 66 insertions, 0 deletions
diff --git a/arch/x86/include/asm/timer.h b/arch/x86/include/asm/timer.h
new file mode 100644
index 000000000000..d0babce4b47a
--- /dev/null
+++ b/arch/x86/include/asm/timer.h
@@ -0,0 +1,66 @@
+#ifndef ASM_X86__TIMER_H
+#define ASM_X86__TIMER_H
+#include <linux/init.h>
+#include <linux/pm.h>
+#include <linux/percpu.h>
+
+#define TICK_SIZE (tick_nsec / 1000)
+
+unsigned long long native_sched_clock(void);
+unsigned long native_calibrate_tsc(void);
+
+#ifdef CONFIG_X86_32
+extern int timer_ack;
+extern int recalibrate_cpu_khz(void);
+#endif /* CONFIG_X86_32 */
+
+extern int no_timer_check;
+
+#ifndef CONFIG_PARAVIRT
+#define calibrate_tsc() native_calibrate_tsc()
+#endif
+
+/* Accelerators for sched_clock()
+ * convert from cycles(64bits) => nanoseconds (64bits)
+ * basic equation:
+ * ns = cycles / (freq / ns_per_sec)
+ * ns = cycles * (ns_per_sec / freq)
+ * ns = cycles * (10^9 / (cpu_khz * 10^3))
+ * ns = cycles * (10^6 / cpu_khz)
+ *
+ * Then we use scaling math (suggested by george@mvista.com) to get:
+ * ns = cycles * (10^6 * SC / cpu_khz) / SC
+ * ns = cycles * cyc2ns_scale / SC
+ *
+ * And since SC is a constant power of two, we can convert the div
+ * into a shift.
+ *
+ * We can use khz divisor instead of mhz to keep a better precision, since
+ * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
+ * (mathieu.desnoyers@polymtl.ca)
+ *
+ * -johnstul@us.ibm.com "math is hard, lets go shopping!"
+ */
+
+DECLARE_PER_CPU(unsigned long, cyc2ns);
+
+#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
+
+static inline unsigned long long __cycles_2_ns(unsigned long long cyc)
+{
+ return cyc * per_cpu(cyc2ns, smp_processor_id()) >> CYC2NS_SCALE_FACTOR;
+}
+
+static inline unsigned long long cycles_2_ns(unsigned long long cyc)
+{
+ unsigned long long ns;
+ unsigned long flags;
+
+ local_irq_save(flags);
+ ns = __cycles_2_ns(cyc);
+ local_irq_restore(flags);
+
+ return ns;
+}
+
+#endif /* ASM_X86__TIMER_H */