Subject:[ACPI]:Add boot option of "idle=nomwait" to disable mwait for CPU C-states From: Zhao Yakui <yakui.zhao@xxxxxxxxx> Add the boot option of "idle=nomwait" to disable Mwait for CPU C-states. If the boot option of "idle=nomwait" is added , OSPM should not use mwait for cpu idle even when the mwait is supported. In such case the C2C3_FFH access mode will be disabled. http://bugzilla.kernel.org/show_bug.cgi?id=10807 Signed-off-by: Zhao Yakui <yakui.zhao@xxxxxxxxx> Signed-off-by: Li Shaohua <shaohua.li@xxxxxxxxx> --- Documentation/kernel-parameters.txt | 4 +++- arch/ia64/kernel/process.c | 2 ++ arch/x86/kernel/process.c | 14 ++++++++++++++ drivers/acpi/processor_core.c | 12 ++++++++++++ include/asm-ia64/processor.h | 1 + include/asm-x86/processor.h | 1 + 6 files changed, 33 insertions(+), 1 deletion(-) Index: linux-2.6/Documentation/kernel-parameters.txt =================================================================== --- linux-2.6.orig/Documentation/kernel-parameters.txt +++ linux-2.6/Documentation/kernel-parameters.txt @@ -785,7 +785,7 @@ and is between 256 and 4096 characters. See Documentation/ide/ide.txt. idle= [X86] - Format: idle=poll or idle=mwait, idle = halt + Format: idle=poll or idle=mwait, idle = halt, idle=nomwait Poll forces a polling idle loop that can slightly improves the performance of waking up a idle CPU, but will use a lot of power and make the system run hot. Not recommended. @@ -795,6 +795,8 @@ and is between 256 and 4096 characters. as idle=poll. idle = halt . Halt is forced to be used for CPU idle. In such case C2/C3 won't be used again. + idle = nomwait. disable Mwait for CPU C-state. + In such case C2C3_FFH access mode will be disabled. ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem Claim all unknown PCI IDE storage controllers. Index: linux-2.6/arch/ia64/kernel/process.c =================================================================== --- linux-2.6.orig/arch/ia64/kernel/process.c +++ linux-2.6/arch/ia64/kernel/process.c @@ -55,6 +55,8 @@ void (*ia64_mark_idle)(int); unsigned long boot_option_idle_override = 0; EXPORT_SYMBOL(boot_option_idle_override); +unsigned long idle_nomwait; +EXPORT_SYMBOL(idle_nomwait); void ia64_do_show_stack (struct unw_frame_info *info, void *arg) Index: linux-2.6/arch/x86/kernel/process.c =================================================================== --- linux-2.6.orig/arch/x86/kernel/process.c +++ linux-2.6/arch/x86/kernel/process.c @@ -7,6 +7,10 @@ #include <linux/module.h> #include <linux/pm.h> #include <asm/system.h> +#include <asm/processor.h> + +unsigned long idle_nomwait; +EXPORT_SYMBOL(idle_nomwait); struct kmem_cache *task_xstate_cachep; @@ -172,6 +176,16 @@ static int __init idle_setup(char *str) force_mwait = 1; else if (!strcmp(str, "halt")) pm_idle = default_idle; + else if (!strcmp(str, "nomwait")) { + /* + * If the boot option of "idle=nomwait" is added, + * it means that mwait will be disabled for CPU C2/C3 + * states. In such case it won't touch the variable + * of boot_option_idle_override. + */ + idle_nomwait = 1; + return 0; + } else return -1; Index: linux-2.6/include/asm-ia64/processor.h =================================================================== --- linux-2.6.orig/include/asm-ia64/processor.h +++ linux-2.6/include/asm-ia64/processor.h @@ -763,6 +763,7 @@ prefetchw (const void *x) #define spin_lock_prefetch(x) prefetchw(x) extern unsigned long boot_option_idle_override; +extern unsigned long idle_nomwait; #endif /* !__ASSEMBLY__ */ Index: linux-2.6/include/asm-x86/processor.h =================================================================== --- linux-2.6.orig/include/asm-x86/processor.h +++ linux-2.6/include/asm-x86/processor.h @@ -732,6 +732,7 @@ extern int force_mwait; extern void select_idle_routine(const struct cpuinfo_x86 *c); extern unsigned long boot_option_idle_override; +extern unsigned long idle_nomwait; extern void enable_sep_cpu(void); extern int sysenter_setup(void); Index: linux-2.6/drivers/acpi/processor_core.c =================================================================== --- linux-2.6.orig/drivers/acpi/processor_core.c +++ linux-2.6/drivers/acpi/processor_core.c @@ -267,6 +267,18 @@ static int acpi_processor_set_pdc(struct if (!pdc_in) return status; + if (idle_nomwait) { + /* + * If mwait is disabled for CPU C-states, the C2C3_FFH access + * mode will be disabled in the parameter of _PDC object. + */ + union acpi_object *obj; + u32 *buffer = NULL; + + obj = pdc_in->pointer; + buffer = (u32 *)(obj->buffer.pointer); + buffer[2] &= ~(ACPI_PDC_C_C2C3_FFH); + } status = acpi_evaluate_object(pr->handle, "_PDC", pdc_in, NULL); if (ACPI_FAILURE(status)) -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
