From 5d77b85458f656923b85291a4ff56ed44859ed52 Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Tue, 20 Jul 2010 13:52:00 -0400 Subject: [PATCH] [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 Cc: Naga Chumbalkar Signed-off-by: Dave Jones --- arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c b/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c index ce7cde713e71..01bd25c3c7ca 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); -- 2.20.1