From c1e3b377ad48febba6f91b8ae42c44ee4d4ab45e Mon Sep 17 00:00:00 2001 From: Zhao Yakui Date: Tue, 24 Jun 2008 17:58:53 +0800 Subject: ACPI: Create "idle=halt" bootparam "idle=halt" limits the idle loop to using the halt instruction. No MWAIT, no IO accesses, no C-states deeper than C1. If something is broken in the idle code, "idle=halt" is a less severe workaround than "idle=poll" which disables all power savings. Signed-off-by: Zhao Yakui Signed-off-by: Len Brown Signed-off-by: Andi Kleen --- drivers/acpi/processor_idle.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'drivers') diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index 0fc310e7dfd..c75c7ace8c1 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -41,6 +41,7 @@ #include #include #include +#include /* * Include the apic definitions for x86 to have the APIC timer related defines @@ -57,6 +58,7 @@ #include #include +#include #define ACPI_PROCESSOR_COMPONENT 0x01000000 #define ACPI_PROCESSOR_CLASS "processor" @@ -955,6 +957,17 @@ static int acpi_processor_get_power_info_cst(struct acpi_processor *pr) } else { continue; } + if (cx.type == ACPI_STATE_C1 && idle_halt) { + /* + * In most cases the C1 space_id obtained from + * _CST object is FIXED_HARDWARE access mode. + * But when the option of idle=halt is added, + * the entry_method type should be changed from + * CSTATE_FFH to CSTATE_HALT. + */ + cx.entry_method = ACPI_CSTATE_HALT; + snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI HLT"); + } } else { snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI IOPORT 0x%x", cx.address); @@ -1780,6 +1793,15 @@ int __cpuinit acpi_processor_power_init(struct acpi_processor *pr, return 0; if (!first_run) { + if (idle_halt) { + /* + * When the boot option of "idle=halt" is added, halt + * is used for CPU IDLE. + * In such case C2/C3 is meaningless. So the max_cstate + * is set to one. + */ + max_cstate = 1; + } dmi_check_system(processor_power_dmi_table); max_cstate = acpi_processor_cstate_check(max_cstate); if (max_cstate < ACPI_C_STATES_MAX) -- cgit v1.2.3