Messages in this thread Patch in this message | | | Date | Fri, 13 Mar 2009 18:11:17 -0700 | From | Greg KH <> | Subject | [patch 100/114] x86, hpet: fix for LS21 + HPET = boot hang |
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2.6.28-stable review patch. If anyone has any objections, please let us know.
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From: john stultz <johnstul@us.ibm.com>
commit b13e24644c138d0ddbc451403c30a96b09bfd556 upstream.
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> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- arch/x86/kernel/hpet.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/arch/x86/kernel/hpet.c +++ b/arch/x86/kernel/hpet.c @@ -267,6 +267,8 @@ static void hpet_set_mode(enum clock_eve 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));
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