The patch titled
i386: clockevents fix breakage on Geode/Cyrix PIT implementations
has been added to the -mm tree. Its filename is
i386-clockevents-fix-breakage-on-geode-cyrix-pit.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: i386: clockevents fix breakage on Geode/Cyrix PIT implementations
From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
The PIT has no dedicated mode for shut down. The only way to disable PIT
is to put it into one shot mode. AMD implementations of PIT on Geode (also
observed on Cyrix) are confused by an "empty" transition from
CLOCK_EVT_MODE_UNUSED to CLOCK_EVT_MODE_SHUTDOWN, which puts the PIT into
one shot mode momentarily.
I realized after staring helpless at the bug report
http://bugzilla.kernel.org/show_bug.cgi?id=8027 for quite a while, that the
only change, which might influence the bogomips calibration, is the above
transition during the PIT initialization.
Avoiding the unnecessary switch to oneshot and later to periodic mode fixes
the weird bogomips value and also the resulting slowness.
The fix is confirmed on OLPC and another Geode based box.
Note: this is unrelated to the Dual Core problem discussed here:
http://lkml.org/lkml/2007/3/17/48
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Jordan Crouse <jordan.crouse@xxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Andi Kleen <ak@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/i386/kernel/i8253.c | 10 +++++++++-
1 files changed, 9 insertions(+), 1 deletion(-)
diff -puN arch/i386/kernel/i8253.c~i386-clockevents-fix-breakage-on-geode-cyrix-pit arch/i386/kernel/i8253.c
--- a/arch/i386/kernel/i8253.c~i386-clockevents-fix-breakage-on-geode-cyrix-pit
+++ a/arch/i386/kernel/i8253.c
@@ -47,9 +47,17 @@ static void init_pit_timer(enum clock_ev
outb(LATCH >> 8 , PIT_CH0); /* MSB */
break;
- case CLOCK_EVT_MODE_ONESHOT:
+ /*
+ * Avoid unnecessary state transitions, as it confuses
+ * Geode / Cyrix based boxen.
+ */
case CLOCK_EVT_MODE_SHUTDOWN:
+ if (evt->mode == CLOCK_EVT_MODE_UNUSED)
+ break;
case CLOCK_EVT_MODE_UNUSED:
+ if (evt->mode == CLOCK_EVT_MODE_SHUTDOWN)
+ break;
+ case CLOCK_EVT_MODE_ONESHOT:
/* One shot setup */
outb_p(0x38, PIT_MODE);
udelay(10);
_
Patches currently in -mm which might be from tglx@xxxxxxxxxxxxx are
origin.patch
documentation-sysrqtxt-added-short-description-for-q-timerlist.patch
i386-disable-local-apic-timer-via-command-line-or-dmi.patch
time-fix-formatting-in-proc-timer_list.patch
setup_boot_apic_clock-irq-enable-fix.patch
i386-clockevents-fix-breakage-on-geode-cyrix-pit.patch
git-ieee1394.patch
log-reason-why-tsc-was-marked-unstable.patch
optimize-timespec_trunc.patch
sched-fix-idle-load-balancing-in-softirqd-context.patch
sched-dynticks-idle-load-balancing-v3.patch
-
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