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Diffstat (limited to 'arch/mips/mti-malta/malta-time.c')
-rw-r--r--arch/mips/mti-malta/malta-time.c40
1 files changed, 31 insertions, 9 deletions
diff --git a/arch/mips/mti-malta/malta-time.c b/arch/mips/mti-malta/malta-time.c
index b7bf721eabf5..7407da04f8d6 100644
--- a/arch/mips/mti-malta/malta-time.c
+++ b/arch/mips/mti-malta/malta-time.c
@@ -21,6 +21,7 @@
#include <linux/i8253.h>
#include <linux/init.h>
#include <linux/kernel_stat.h>
+#include <linux/math64.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
@@ -72,6 +73,8 @@ static void __init estimate_frequencies(void)
{
unsigned long flags;
unsigned int count, start;
+ unsigned char secs1, secs2, ctrl;
+ int secs;
cycle_t giccount = 0, gicstart = 0;
#if defined(CONFIG_KVM_GUEST) && CONFIG_KVM_GUEST_TIMER_FREQ
@@ -81,32 +84,51 @@ static void __init estimate_frequencies(void)
local_irq_save(flags);
- /* Start counter exactly on falling edge of update flag. */
+ if (gic_present)
+ gic_start_count();
+
+ /*
+ * Read counters exactly on rising edge of update flag.
+ * This helps get an accurate reading under virtualisation.
+ */
while (CMOS_READ(RTC_REG_A) & RTC_UIP);
while (!(CMOS_READ(RTC_REG_A) & RTC_UIP));
-
- /* Initialize counters. */
start = read_c0_count();
- if (gic_present) {
- gic_start_count();
+ if (gic_present)
gicstart = gic_read_count();
- }
- /* Read counter exactly on falling edge of update flag. */
+ /* Wait for falling edge before reading RTC. */
while (CMOS_READ(RTC_REG_A) & RTC_UIP);
- while (!(CMOS_READ(RTC_REG_A) & RTC_UIP));
+ secs1 = CMOS_READ(RTC_SECONDS);
+ /* Read counters again exactly on rising edge of update flag. */
+ while (!(CMOS_READ(RTC_REG_A) & RTC_UIP));
count = read_c0_count();
if (gic_present)
giccount = gic_read_count();
+ /* Wait for falling edge before reading RTC again. */
+ while (CMOS_READ(RTC_REG_A) & RTC_UIP);
+ secs2 = CMOS_READ(RTC_SECONDS);
+
+ ctrl = CMOS_READ(RTC_CONTROL);
+
local_irq_restore(flags);
+ if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
+ secs1 = bcd2bin(secs1);
+ secs2 = bcd2bin(secs2);
+ }
+ secs = secs2 - secs1;
+ if (secs < 1)
+ secs += 60;
+
count -= start;
+ count /= secs;
mips_hpt_frequency = count;
if (gic_present) {
- giccount -= gicstart;
+ giccount = div_u64(giccount - gicstart, secs);
gic_frequency = giccount;
}
}