diff options
| author | Matthew Garrett <mjg@redhat.com> | 2010-07-20 13:52:00 -0400 |
|---|---|---|
| committer | Dave Jones <davej@redhat.com> | 2010-08-03 13:47:02 -0400 |
| commit | 5d77b85458f656923b85291a4ff56ed44859ed52 (patch) | |
| tree | 2c6486e767ec0007a01db589b8eec05d90d148a0 /arch/x86/kernel/cpu | |
| parent | cad70a6ae5aaef4641a3efdfd536c30f13891afe (diff) | |
[CPUFREQ] pcc driver should check for pcch method before calling _OSC
The pcc specification documents an _OSC method that's incompatible with the
one defined as part of the ACPI spec. This shouldn't be a problem as both
are supposed to be guarded with a UUID. Unfortunately approximately nobody
(including HP, who wrote this spec) properly check the UUID on entry to the
_OSC call. Right now this could result in surprising behaviour if the pcc
driver performs an _OSC call on a machine that doesn't implement the pcc
specification. Check whether the PCCH method exists first in order to reduce
this probability.
Signed-off-by: Matthew Garrett <mjg@redhat.com>
Cc: Naga Chumbalkar <nagananda.chumbalkar@hp.com>
Signed-off-by: Dave Jones <davej@redhat.com>
Diffstat (limited to 'arch/x86/kernel/cpu')
| -rw-r--r-- | arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c b/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c index ce7cde713e7..01bd25c3c7c 100644 --- a/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c +++ b/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c @@ -397,13 +397,17 @@ static int __init pcc_cpufreq_probe(void) struct pcc_memory_resource *mem_resource; struct pcc_register_resource *reg_resource; union acpi_object *out_obj, *member; - acpi_handle handle, osc_handle; + acpi_handle handle, osc_handle, pcch_handle; int ret = 0; status = acpi_get_handle(NULL, "\\_SB", &handle); if (ACPI_FAILURE(status)) return -ENODEV; + status = acpi_get_handle(handle, "PCCH", &pcch_handle); + if (ACPI_FAILURE(status)) + return -ENODEV; + status = acpi_get_handle(handle, "_OSC", &osc_handle); if (ACPI_SUCCESS(status)) { ret = pcc_cpufreq_do_osc(&osc_handle); |