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authorjohn stultz <johnstul@us.ibm.com>2009-02-12 18:48:53 -0800
committerIngo Molnar <mingo@elte.hu>2009-02-13 09:15:46 +0100
commitb13e24644c138d0ddbc451403c30a96b09bfd556 (patch)
tree5ce9c5d1885c78bee5da87fe2cd0d4fb0efccbf2 /arch/x86/kernel/hpet.c
parent7ad9de6ac83bd825996d2de98c92e0f425c31050 (diff)
x86, hpet: fix for LS21 + HPET = boot hang
Between 2.6.23 and 2.6.24-rc1 a change was made that broke IBM LS21 systems that had the HPET enabled in the BIOS, resulting in boot hangs for x86_64. Specifically commit b8ce33590687888ebb900d09557b8807c4539022, which merges the i386 and x86_64 HPET code. Prior to this commit, when we setup the HPET timers in x86_64, we did the following: hpet_writel(HPET_TN_ENABLE | HPET_TN_PERIODIC | HPET_TN_SETVAL | HPET_TN_32BIT, HPET_T0_CFG); However after the i386/x86_64 HPET merge, we do the following: cfg = hpet_readl(HPET_Tn_CFG(timer)); cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC | HPET_TN_SETVAL | HPET_TN_32BIT; hpet_writel(cfg, HPET_Tn_CFG(timer)); However on LS21s with HPET enabled in the BIOS, the HPET_T0_CFG register boots with Level triggered interrupts (HPET_TN_LEVEL) enabled. This causes the periodic interrupt to be not so periodic, and that results in the boot time hang I reported earlier in the delay calibration. My fix: Always disable HPET_TN_LEVEL when setting up periodic mode. Signed-off-by: John Stultz <johnstul@us.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/kernel/hpet.c')
-rw-r--r--arch/x86/kernel/hpet.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index 64d5ad0b8ad..5c8da2c2c18 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -269,6 +269,8 @@ static void hpet_set_mode(enum clock_event_mode mode,
now = hpet_readl(HPET_COUNTER);
cmp = now + (unsigned long) delta;
cfg = hpet_readl(HPET_Tn_CFG(timer));
+ /* Make sure we use edge triggered interrupts */
+ cfg &= ~HPET_TN_LEVEL;
cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC |
HPET_TN_SETVAL | HPET_TN_32BIT;
hpet_writel(cfg, HPET_Tn_CFG(timer));