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Diffstat (limited to 'arch/x86/kernel/hpet.c')
-rw-r--r--arch/x86/kernel/hpet.c63
1 files changed, 22 insertions, 41 deletions
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index 9b5cfcdfc426..0ea6a19bfdfe 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -17,7 +17,7 @@
/* FSEC = 10^-15
NSEC = 10^-9 */
-#define FSEC_PER_NSEC 1000000
+#define FSEC_PER_NSEC 1000000L
/*
* HPET address is set in acpi/boot.c, when an ACPI entry exists
@@ -36,26 +36,15 @@ static inline void hpet_writel(unsigned long d, unsigned long a)
}
#ifdef CONFIG_X86_64
-
#include <asm/pgtable.h>
-
-static inline void hpet_set_mapping(void)
-{
- set_fixmap_nocache(FIX_HPET_BASE, hpet_address);
- __set_fixmap(VSYSCALL_HPET, hpet_address, PAGE_KERNEL_VSYSCALL_NOCACHE);
- hpet_virt_address = (void __iomem *)fix_to_virt(FIX_HPET_BASE);
-}
-
-static inline void hpet_clear_mapping(void)
-{
- hpet_virt_address = NULL;
-}
-
-#else
+#endif
static inline void hpet_set_mapping(void)
{
hpet_virt_address = ioremap_nocache(hpet_address, HPET_MMAP_SIZE);
+#ifdef CONFIG_X86_64
+ __set_fixmap(VSYSCALL_HPET, hpet_address, PAGE_KERNEL_VSYSCALL_NOCACHE);
+#endif
}
static inline void hpet_clear_mapping(void)
@@ -63,7 +52,6 @@ static inline void hpet_clear_mapping(void)
iounmap(hpet_virt_address);
hpet_virt_address = NULL;
}
-#endif
/*
* HPET command line enable / disable
@@ -206,20 +194,19 @@ static void hpet_enable_legacy_int(void)
static void hpet_legacy_clockevent_register(void)
{
- uint64_t hpet_freq;
-
/* Start HPET legacy interrupts */
hpet_enable_legacy_int();
/*
- * The period is a femto seconds value. We need to calculate the
- * scaled math multiplication factor for nanosecond to hpet tick
- * conversion.
+ * The mult factor is defined as (include/linux/clockchips.h)
+ * mult/2^shift = cyc/ns (in contrast to ns/cyc in clocksource.h)
+ * hpet_period is in units of femtoseconds (per cycle), so
+ * mult/2^shift = cyc/ns = 10^6/hpet_period
+ * mult = (10^6 * 2^shift)/hpet_period
+ * mult = (FSEC_PER_NSEC << hpet_clockevent.shift)/hpet_period
*/
- hpet_freq = 1000000000000000ULL;
- do_div(hpet_freq, hpet_period);
- hpet_clockevent.mult = div_sc((unsigned long) hpet_freq,
- NSEC_PER_SEC, hpet_clockevent.shift);
+ hpet_clockevent.mult = div_sc((unsigned long) FSEC_PER_NSEC,
+ hpet_period, hpet_clockevent.shift);
/* Calculate the min / max delta */
hpet_clockevent.max_delta_ns = clockevent_delta2ns(0x7FFFFFFF,
&hpet_clockevent);
@@ -324,7 +311,7 @@ static struct clocksource clocksource_hpet = {
static int hpet_clocksource_register(void)
{
- u64 tmp, start, now;
+ u64 start, now;
cycle_t t1;
/* Start the counter */
@@ -351,21 +338,15 @@ static int hpet_clocksource_register(void)
return -ENODEV;
}
- /* Initialize and register HPET clocksource
- *
- * hpet period is in femto seconds per cycle
- * so we need to convert this to ns/cyc units
- * approximated by mult/2^shift
- *
- * fsec/cyc * 1nsec/1000000fsec = nsec/cyc = mult/2^shift
- * fsec/cyc * 1ns/1000000fsec * 2^shift = mult
- * fsec/cyc * 2^shift * 1nsec/1000000fsec = mult
- * (fsec/cyc << shift)/1000000 = mult
- * (hpet_period << shift)/FSEC_PER_NSEC = mult
+ /*
+ * The definition of mult is (include/linux/clocksource.h)
+ * mult/2^shift = ns/cyc and hpet_period is in units of fsec/cyc
+ * so we first need to convert hpet_period to ns/cyc units:
+ * mult/2^shift = ns/cyc = hpet_period/10^6
+ * mult = (hpet_period * 2^shift)/10^6
+ * mult = (hpet_period << shift)/FSEC_PER_NSEC
*/
- tmp = (u64)hpet_period << HPET_SHIFT;
- do_div(tmp, FSEC_PER_NSEC);
- clocksource_hpet.mult = (u32)tmp;
+ clocksource_hpet.mult = div_sc(hpet_period, FSEC_PER_NSEC, HPET_SHIFT);
clocksource_register(&clocksource_hpet);