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authorjohn stultz <johnstul@us.ibm.com>2005-06-23 00:08:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-23 09:45:12 -0700
commita3a00751ad8970c13d0563c2e92ee68c655a8e6b (patch)
treea351e629e1e29e2fef7d82ef53548d575f4a1fc4 /arch
parentc0a88c987878e533fc21fbf684198021a3b2c279 (diff)
[PATCH] x86_64: fix hpet for systems that don't support legacy replacement
Currently the x86-64 HPET code assumes the entire HPET implementation from the spec is present. This breaks on boxes that do not implement the optional legacy timer replacement functionality portion of the spec. This patch fixes this issue, allowing x86-64 systems that cannot use the HPET for the timer interrupt and RTC to still use the HPET as a time source. I've tested this patch on a system systems without HPET, with HPET but without legacy timer replacement, as well as HPET with legacy timer replacement. This version adds a minor check to cap the HPET counter value in gettimeoffset_hpet to avoid possible time inconsistencies. Please ignore the A2 version I sent to you earlier. Acked-by: Andi Kleen <ak@muc.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86_64/kernel/time.c42
1 files changed, 28 insertions, 14 deletions
diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
index fb8c809b4cd..66bf6ddeb0c 100644
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -64,6 +64,7 @@ static int notsc __initdata = 0;
unsigned int cpu_khz; /* TSC clocks / usec, not used here */
static unsigned long hpet_period; /* fsecs / HPET clock */
unsigned long hpet_tick; /* HPET clocks / interrupt */
+static int hpet_use_timer;
unsigned long vxtime_hz = PIT_TICK_RATE;
int report_lost_ticks; /* command line option */
unsigned long long monotonic_base;
@@ -105,7 +106,9 @@ static inline unsigned int do_gettimeoffset_tsc(void)
static inline unsigned int do_gettimeoffset_hpet(void)
{
- return ((hpet_readl(HPET_COUNTER) - vxtime.last) * vxtime.quot) >> 32;
+ /* cap counter read to one tick to avoid inconsistencies */
+ unsigned long counter = hpet_readl(HPET_COUNTER) - vxtime.last;
+ return (min(counter,hpet_tick) * vxtime.quot) >> 32;
}
unsigned int (*do_gettimeoffset)(void) = do_gettimeoffset_tsc;
@@ -301,7 +304,7 @@ unsigned long long monotonic_clock(void)
last_offset = vxtime.last;
base = monotonic_base;
- this_offset = hpet_readl(HPET_T0_CMP) - hpet_tick;
+ this_offset = hpet_readl(HPET_COUNTER);
} while (read_seqretry(&xtime_lock, seq));
offset = (this_offset - last_offset);
@@ -377,7 +380,14 @@ static irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
write_seqlock(&xtime_lock);
- if (vxtime.hpet_address) {
+ if (vxtime.hpet_address)
+ offset = hpet_readl(HPET_COUNTER);
+
+ if (hpet_use_timer) {
+ /* if we're using the hpet timer functionality,
+ * we can more accurately know the counter value
+ * when the timer interrupt occured.
+ */
offset = hpet_readl(HPET_T0_CMP) - hpet_tick;
delay = hpet_readl(HPET_COUNTER) - offset;
} else {
@@ -803,17 +813,18 @@ static int hpet_timer_stop_set_go(unsigned long tick)
* Set up timer 0, as periodic with first interrupt to happen at hpet_tick,
* and period also hpet_tick.
*/
-
- hpet_writel(HPET_TN_ENABLE | HPET_TN_PERIODIC | HPET_TN_SETVAL |
+ if (hpet_use_timer) {
+ hpet_writel(HPET_TN_ENABLE | HPET_TN_PERIODIC | HPET_TN_SETVAL |
HPET_TN_32BIT, HPET_T0_CFG);
- hpet_writel(hpet_tick, HPET_T0_CMP);
- hpet_writel(hpet_tick, HPET_T0_CMP); /* AK: why twice? */
-
+ hpet_writel(hpet_tick, HPET_T0_CMP);
+ hpet_writel(hpet_tick, HPET_T0_CMP); /* AK: why twice? */
+ cfg |= HPET_CFG_LEGACY;
+ }
/*
* Go!
*/
- cfg |= HPET_CFG_ENABLE | HPET_CFG_LEGACY;
+ cfg |= HPET_CFG_ENABLE;
hpet_writel(cfg, HPET_CFG);
return 0;
@@ -834,8 +845,7 @@ static int hpet_init(void)
id = hpet_readl(HPET_ID);
- if (!(id & HPET_ID_VENDOR) || !(id & HPET_ID_NUMBER) ||
- !(id & HPET_ID_LEGSUP))
+ if (!(id & HPET_ID_VENDOR) || !(id & HPET_ID_NUMBER))
return -1;
hpet_period = hpet_readl(HPET_PERIOD);
@@ -845,6 +855,8 @@ static int hpet_init(void)
hpet_tick = (1000000000L * (USEC_PER_SEC / HZ) + hpet_period / 2) /
hpet_period;
+ hpet_use_timer = (id & HPET_ID_LEGSUP);
+
return hpet_timer_stop_set_go(hpet_tick);
}
@@ -901,9 +913,11 @@ void __init time_init(void)
set_normalized_timespec(&wall_to_monotonic,
-xtime.tv_sec, -xtime.tv_nsec);
- if (!hpet_init()) {
+ if (!hpet_init())
vxtime_hz = (1000000000000000L + hpet_period / 2) /
hpet_period;
+
+ if (hpet_use_timer) {
cpu_khz = hpet_calibrate_tsc();
timename = "HPET";
#ifdef CONFIG_X86_PM_TIMER
@@ -968,7 +982,7 @@ void __init time_init_gtod(void)
if (unsynchronized_tsc())
notsc = 1;
if (vxtime.hpet_address && notsc) {
- timetype = "HPET";
+ timetype = hpet_use_timer ? "HPET" : "PIT/HPET";
vxtime.last = hpet_readl(HPET_T0_CMP) - hpet_tick;
vxtime.mode = VXTIME_HPET;
do_gettimeoffset = do_gettimeoffset_hpet;
@@ -983,7 +997,7 @@ void __init time_init_gtod(void)
printk(KERN_INFO "Disabling vsyscall due to use of PM timer\n");
#endif
} else {
- timetype = vxtime.hpet_address ? "HPET/TSC" : "PIT/TSC";
+ timetype = hpet_use_timer ? "HPET/TSC" : "PIT/TSC";
vxtime.mode = VXTIME_TSC;
}