If x86 CPU implementation of the MWAIT instruction reasonably

interacts with interrupts, query ACPI and use MWAIT for entrance into
Cx sleep states.  Support C1 "I/O then halt" mode.  See Intel'
document 302223-007 "Intelб╝ Processor Vendor-Specific ACPI Interface
Specification" for description.

Move the acpi_cpu_c1() function into x86/cpu_machdep.c and use
it instead of inlining "sti; hlt" sequence in several places.

In the acpi(4) man page, besides documenting the dev.cpu.N.cx_methods
sysctl, correct the names for dev.cpu.N.{cx_usage,cx_lowest,cx_supported}
sysctls.

Both jkim and avg have some other patches implementing the mwait
functionality; this work is unrelated.  Linux does not rely on the
ACPI to provide correct tables describing Cx modes.  Instead, the
driver has pre-defined knowledge of the CPU models, it was supplied by
Intel.

Tested by:    pho (previous versions)
Sponsored by:	The FreeBSD Foundation

2 files changed, 1 insertions, 7 deletions

diff --git a/sys/i386/acpica/acpi_machdep.c b/sys/i386/acpica/acpi_machdep.c
index 049354b0c213..4c79691dbeee 100644
--- a/sys/i386/acpica/acpi_machdep.c
+++ b/sys/i386/acpica/acpi_machdep.c
@@ -106,13 +106,6 @@ acpi_machdep_quirks(int *quirks)
 	return (0);
 }
 
-void
-acpi_cpu_c1()
-{
-
-	__asm __volatile("sti; hlt");
-}
-
 /*
  * Support for mapping ACPI tables during early boot.  This abuses the
  * crashdump map because the kernel cannot allocate KVA in
diff --git a/sys/i386/include/md_var.h b/sys/i386/include/md_var.h
index bffdd5751d66..b5bd35ef524d 100644
--- a/sys/i386/include/md_var.h
+++ b/sys/i386/include/md_var.h
@@ -97,6 +97,7 @@ struct	dumperinfo;
 void	*alloc_fpusave(int flags);
 void	bcopyb(const void *from, void *to, size_t len);
 void	busdma_swi(void);
+bool	cpu_mwait_usable(void);
 void	cpu_probe_amdc1e(void);
 void	cpu_setregs(void);
 void	cpu_switch_load_gs(void) __asm(__STRING(cpu_switch_load_gs));