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-rw-r--r--arch/x86/kernel/hpet.c26
1 files changed, 16 insertions, 10 deletions
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index ae03cab4352e..4ff5968f12d2 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -27,6 +27,9 @@
#define HPET_DEV_FSB_CAP 0x1000
#define HPET_DEV_PERI_CAP 0x2000
+#define HPET_MIN_CYCLES 128
+#define HPET_MIN_PROG_DELTA (HPET_MIN_CYCLES + (HPET_MIN_CYCLES >> 1))
+
#define EVT_TO_HPET_DEV(evt) container_of(evt, struct hpet_dev, evt)
/*
@@ -299,8 +302,9 @@ static void hpet_legacy_clockevent_register(void)
/* Calculate the min / max delta */
hpet_clockevent.max_delta_ns = clockevent_delta2ns(0x7FFFFFFF,
&hpet_clockevent);
- /* 5 usec minimum reprogramming delta. */
- hpet_clockevent.min_delta_ns = 5000;
+ /* Setup minimum reprogramming delta. */
+ hpet_clockevent.min_delta_ns = clockevent_delta2ns(HPET_MIN_PROG_DELTA,
+ &hpet_clockevent);
/*
* Start hpet with the boot cpu mask and make it
@@ -393,22 +397,24 @@ static int hpet_next_event(unsigned long delta,
* the wraparound into account) nor a simple count down event
* mode. Further the write to the comparator register is
* delayed internally up to two HPET clock cycles in certain
- * chipsets (ATI, ICH9,10). We worked around that by reading
- * back the compare register, but that required another
- * workaround for ICH9,10 chips where the first readout after
- * write can return the old stale value. We already have a
- * minimum delta of 5us enforced, but a NMI or SMI hitting
+ * chipsets (ATI, ICH9,10). Some newer AMD chipsets have even
+ * longer delays. We worked around that by reading back the
+ * compare register, but that required another workaround for
+ * ICH9,10 chips where the first readout after write can
+ * return the old stale value. We already had a minimum
+ * programming delta of 5us enforced, but a NMI or SMI hitting
* between the counter readout and the comparator write can
* move us behind that point easily. Now instead of reading
* the compare register back several times, we make the ETIME
* decision based on the following: Return ETIME if the
- * counter value after the write is less than 8 HPET cycles
+ * counter value after the write is less than HPET_MIN_CYCLES
* away from the event or if the counter is already ahead of
- * the event.
+ * the event. The minimum programming delta for the generic
+ * clockevents code is set to 1.5 * HPET_MIN_CYCLES.
*/
res = (s32)(cnt - hpet_readl(HPET_COUNTER));
- return res < 8 ? -ETIME : 0;
+ return res < HPET_MIN_CYCLES ? -ETIME : 0;
}
static void hpet_legacy_set_mode(enum clock_event_mode mode,
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