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| author | Thomas Gleixner <tglx@linutronix.de> | 2007-07-21 17:11:12 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2007-08-09 14:27:37 -0700 |
| commit | 3ee3cf9d25b563e1adb4e6515cb5c337b54e88fb (patch) | |
| tree | 81352bd8a083315d67b3e4a3022495bba9662056 | |
| parent | 2d68c23353ff6e72ca62a4d355f09332382d6796 (diff) | |
| download | lwn-3ee3cf9d25b563e1adb4e6515cb5c337b54e88fb.tar.gz lwn-3ee3cf9d25b563e1adb4e6515cb5c337b54e88fb.zip | |
i386: HPET, check if the counter works
Some systems have a HPET which is not incrementing, which leads to a
complete hang. Detect it during HPET setup.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | arch/i386/kernel/hpet.c | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/arch/i386/kernel/hpet.c b/arch/i386/kernel/hpet.c index 17d73459fc5f..cbb47519e0cf 100644 --- a/arch/i386/kernel/hpet.c +++ b/arch/i386/kernel/hpet.c @@ -226,7 +226,8 @@ int __init hpet_enable(void) { unsigned long id; uint64_t hpet_freq; - u64 tmp; + u64 tmp, start, now; + cycle_t t1; if (!is_hpet_capable()) return 0; @@ -273,6 +274,27 @@ int __init hpet_enable(void) /* Start the counter */ hpet_start_counter(); + /* Verify whether hpet counter works */ + t1 = read_hpet(); + rdtscll(start); + + /* + * We don't know the TSC frequency yet, but waiting for + * 200000 TSC cycles is safe: + * 4 GHz == 50us + * 1 GHz == 200us + */ + do { + rep_nop(); + rdtscll(now); + } while ((now - start) < 200000UL); + + if (t1 == read_hpet()) { + printk(KERN_WARNING + "HPET counter not counting. HPET disabled\n"); + goto out_nohpet; + } + /* Initialize and register HPET clocksource * * hpet period is in femto seconds per cycle |