diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2007-07-21 17:11:12 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-07-21 18:37:12 -0700 |
| commit | 075bcd1f9726b8a1caff86eda06f29f71fb21235 (patch) | |
| tree | 992a8717dbe7b17fa80cd10f47c3dc639f395aa2 /arch/i386/kernel/hpet.c | |
| parent | df2edcf3b6ba54d9ffa620e322583cd994a6e54a (diff) | |
| download | lwn-075bcd1f9726b8a1caff86eda06f29f71fb21235.tar.gz lwn-075bcd1f9726b8a1caff86eda06f29f71fb21235.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>
Cc: john stultz <johnstul@us.ibm.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/i386/kernel/hpet.c')
| -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 662d7976a9ea..b93310d11950 100644 --- a/arch/i386/kernel/hpet.c +++ b/arch/i386/kernel/hpet.c @@ -232,7 +232,8 @@ 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; @@ -279,6 +280,27 @@ 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 |