Linux-libre 4.7.1-gnupck-4.7.1-gnu

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 b7bf721ea..7407da04f 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;
 	}
 }