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Commit | Line | Data |
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2cb7cef9 BS |
1 | From: john stultz <johnstul@us.ibm.com> |
2 | Date: Fri, 13 Feb 2009 02:48:53 +0000 (-0800) | |
3 | Subject: x86, hpet: fix for LS21 + HPET = boot hang | |
4 | Patch-mainline: 2.6.29-rc6 | |
5 | Git-commit: b13e24644c138d0ddbc451403c30a96b09bfd556 | |
6 | References: bnc#476877 | |
7 | ||
8 | x86, hpet: fix for LS21 + HPET = boot hang | |
9 | ||
10 | Between 2.6.23 and 2.6.24-rc1 a change was made that broke IBM LS21 | |
11 | systems that had the HPET enabled in the BIOS, resulting in boot hangs | |
12 | for x86_64. | |
13 | ||
14 | Specifically commit b8ce33590687888ebb900d09557b8807c4539022, which | |
15 | merges the i386 and x86_64 HPET code. | |
16 | ||
17 | Prior to this commit, when we setup the HPET timers in x86_64, we did | |
18 | the following: | |
19 | ||
20 | hpet_writel(HPET_TN_ENABLE | HPET_TN_PERIODIC | HPET_TN_SETVAL | | |
21 | HPET_TN_32BIT, HPET_T0_CFG); | |
22 | ||
23 | However after the i386/x86_64 HPET merge, we do the following: | |
24 | ||
25 | cfg = hpet_readl(HPET_Tn_CFG(timer)); | |
26 | cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC | | |
27 | HPET_TN_SETVAL | HPET_TN_32BIT; | |
28 | hpet_writel(cfg, HPET_Tn_CFG(timer)); | |
29 | ||
30 | However on LS21s with HPET enabled in the BIOS, the HPET_T0_CFG register | |
31 | boots with Level triggered interrupts (HPET_TN_LEVEL) enabled. This | |
32 | causes the periodic interrupt to be not so periodic, and that results in | |
33 | the boot time hang I reported earlier in the delay calibration. | |
34 | ||
35 | My fix: Always disable HPET_TN_LEVEL when setting up periodic mode. | |
36 | ||
37 | Signed-off-by: John Stultz <johnstul@us.ibm.com> | |
38 | Signed-off-by: Ingo Molnar <mingo@elte.hu> | |
39 | Acked-by: Jeff Mahoney <jeffm@suse.com> | |
40 | --- | |
41 | ||
42 | --- | |
43 | arch/x86/kernel/hpet.c | 2 ++ | |
44 | 1 file changed, 2 insertions(+) | |
45 | ||
46 | --- a/arch/x86/kernel/hpet.c | |
47 | +++ b/arch/x86/kernel/hpet.c | |
48 | @@ -304,6 +304,8 @@ static void hpet_legacy_set_mode(enum cl | |
49 | now = hpet_read_value(HPET_COUNTER); | |
50 | cmp = now + (unsigned long) delta; | |
51 | cfg = hpet_readl(HPET_T0_CFG); | |
52 | + /* Make sure we use edge triggered interrupts */ | |
53 | + cfg &= ~HPET_TN_LEVEL; | |
54 | cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC | | |
55 | HPET_TN_SETVAL | | |
56 | (hpet_legacy_use_64_bits ? 0 : HPET_TN_32BIT); |