ACPI: Processor native C-states using MWAIT
Intel processors starting with the Core Duo support
support processor native C-state using the MWAIT instruction.
Refer: Intel Architecture Software Developer's Manual
http://www.intel.com/design/Pentium4/manuals/253668.htm
Platform firmware exports the support for Native C-state to OS using
ACPI _PDC and _CST methods.
Refer: Intel Processor Vendor-Specific ACPI: Interface Specification
http://www.intel.com/technology/iapc/acpi/downloads/302223.htm
With Processor Native C-state, we use 'MWAIT' instruction on the processor
to enter different C-states (C1, C2, C3). We won't use the special IO
ports to enter C-state and no SMM mode etc required to enter C-state.
Overall this will mean better C-state support.
One major advantage of using MWAIT for all C-states is, with this and
"treat interrupt as break event" feature of MWAIT, we can now get accurate
timing for the time spent in C1, C2, .. states.
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/arch/i386/kernel/acpi/cstate.c b/arch/i386/kernel/acpi/cstate.c
index 25db49e..20563e5 100644
--- a/arch/i386/kernel/acpi/cstate.c
+++ b/arch/i386/kernel/acpi/cstate.c
@@ -10,6 +10,7 @@
#include <linux/module.h>
#include <linux/init.h>
#include <linux/acpi.h>
+#include <linux/cpu.h>
#include <acpi/processor.h>
#include <asm/acpi.h>
@@ -41,5 +42,124 @@
flags->bm_check = 1;
}
}
-
EXPORT_SYMBOL(acpi_processor_power_init_bm_check);
+
+/* The code below handles cstate entry with monitor-mwait pair on Intel*/
+
+struct cstate_entry_s {
+ struct {
+ unsigned int eax;
+ unsigned int ecx;
+ } states[ACPI_PROCESSOR_MAX_POWER];
+};
+static struct cstate_entry_s *cpu_cstate_entry; /* per CPU ptr */
+
+static short mwait_supported[ACPI_PROCESSOR_MAX_POWER];
+
+#define MWAIT_SUBSTATE_MASK (0xf)
+#define MWAIT_SUBSTATE_SIZE (4)
+
+#define CPUID_MWAIT_LEAF (5)
+#define CPUID5_ECX_EXTENSIONS_SUPPORTED (0x1)
+#define CPUID5_ECX_INTERRUPT_BREAK (0x2)
+
+#define MWAIT_ECX_INTERRUPT_BREAK (0x1)
+
+#define NATIVE_CSTATE_BEYOND_HALT (2)
+
+int acpi_processor_ffh_cstate_probe(unsigned int cpu,
+ struct acpi_processor_cx *cx, struct acpi_power_register *reg)
+{
+ struct cstate_entry_s *percpu_entry;
+ struct cpuinfo_x86 *c = cpu_data + cpu;
+
+ cpumask_t saved_mask;
+ int retval;
+ unsigned int eax, ebx, ecx, edx;
+ unsigned int edx_part;
+ unsigned int cstate_type; /* C-state type and not ACPI C-state type */
+ unsigned int num_cstate_subtype;
+
+ if (!cpu_cstate_entry || c->cpuid_level < CPUID_MWAIT_LEAF )
+ return -1;
+
+ if (reg->bit_offset != NATIVE_CSTATE_BEYOND_HALT)
+ return -1;
+
+ percpu_entry = per_cpu_ptr(cpu_cstate_entry, cpu);
+ percpu_entry->states[cx->index].eax = 0;
+ percpu_entry->states[cx->index].ecx = 0;
+
+ /* Make sure we are running on right CPU */
+ saved_mask = current->cpus_allowed;
+ retval = set_cpus_allowed(current, cpumask_of_cpu(cpu));
+ if (retval)
+ return -1;
+
+ cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);
+
+ /* Check whether this particular cx_type (in CST) is supported or not */
+ cstate_type = (cx->address >> MWAIT_SUBSTATE_SIZE) + 1;
+ edx_part = edx >> (cstate_type * MWAIT_SUBSTATE_SIZE);
+ num_cstate_subtype = edx_part & MWAIT_SUBSTATE_MASK;
+
+ retval = 0;
+ if (num_cstate_subtype < (cx->address & MWAIT_SUBSTATE_MASK)) {
+ retval = -1;
+ goto out;
+ }
+
+ /* mwait ecx extensions INTERRUPT_BREAK should be supported for C2/C3 */
+ if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
+ !(ecx & CPUID5_ECX_INTERRUPT_BREAK)) {
+ retval = -1;
+ goto out;
+ }
+ percpu_entry->states[cx->index].ecx = MWAIT_ECX_INTERRUPT_BREAK;
+
+ /* Use the hint in CST */
+ percpu_entry->states[cx->index].eax = cx->address;
+
+ if (!mwait_supported[cstate_type]) {
+ mwait_supported[cstate_type] = 1;
+ printk(KERN_DEBUG "Monitor-Mwait will be used to enter C-%d "
+ "state\n", cx->type);
+ }
+
+out:
+ set_cpus_allowed(current, saved_mask);
+ return retval;
+}
+EXPORT_SYMBOL_GPL(acpi_processor_ffh_cstate_probe);
+
+void acpi_processor_ffh_cstate_enter(struct acpi_processor_cx *cx)
+{
+ unsigned int cpu = smp_processor_id();
+ struct cstate_entry_s *percpu_entry;
+
+ percpu_entry = per_cpu_ptr(cpu_cstate_entry, cpu);
+ mwait_idle_with_hints(percpu_entry->states[cx->index].eax,
+ percpu_entry->states[cx->index].ecx);
+}
+EXPORT_SYMBOL_GPL(acpi_processor_ffh_cstate_enter);
+
+static int __init ffh_cstate_init(void)
+{
+ struct cpuinfo_x86 *c = &boot_cpu_data;
+ if (c->x86_vendor != X86_VENDOR_INTEL)
+ return -1;
+
+ cpu_cstate_entry = alloc_percpu(struct cstate_entry_s);
+ return 0;
+}
+
+static void __exit ffh_cstate_exit(void)
+{
+ if (cpu_cstate_entry) {
+ free_percpu(cpu_cstate_entry);
+ cpu_cstate_entry = NULL;
+ }
+}
+
+arch_initcall(ffh_cstate_init);
+__exitcall(ffh_cstate_exit);