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authorMatthew Garrett <mjg@redhat.com>2010-07-20 13:52:00 -0400
committerDave Jones <davej@redhat.com>2010-07-26 15:25:34 -0400
commit47f8bcf362410b631a4d99ff5c79ec6b9dd3ace6 (patch)
tree2c6486e767ec0007a01db589b8eec05d90d148a0 /arch
parent6f90388ac98e8cb2c63e307ffb13871a6b87f29b (diff)
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[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')
-rw-r--r--arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c6
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);