Date:	Wed, 26 May 2010 22:42:31 -0400
From:	Len Brown <lenb@...nel.org>
To:	x86@...nel.org, linux-pm@...ts.linux-foundation.org
Cc:	linux-kernel@...r.kernel.org, Len Brown <len.brown@...el.com>
Subject: [PATCH 8/8] intel_idle: create a native cpuidle driver for select
 intel processors

From: Len Brown <len.brown@...el.com>

This EXPERIMENTAL driver supersedes acpi_idle
on modern Intel processors. (Nehalem and Atom Processors).

For CONFIG_INTEL_IDLE=y, intel_idle probes before acpi_idle,
no matter if CONFIG_ACPI_PROCESSOR=y or =m.

Boot with "intel_idle.max_cstate=0" to disable the driver
and to fall back on ACPI.

CONFIG_INTEL_IDLE=m is not recommended unless the system
has a method to guarantee intel_idle loads before ACPI's
processor_idle.

This driver does not yet know about cpu online/offline
and thus will not yet play well with cpu-hotplug.

Signed-off-by: Len Brown <len.brown@...el.com>
---
 MAINTAINERS                     |    7 +
 drivers/Makefile                |    2 +-
 drivers/acpi/processor_driver.c |    6 +-
 drivers/idle/Kconfig            |   11 +
 drivers/idle/Makefile           |    1 +
 drivers/idle/intel_idle.c       |  446 +++++++++++++++++++++++++++++++++++++++
 6 files changed, 471 insertions(+), 2 deletions(-)
 create mode 100755 drivers/idle/intel_idle.c

diff --git a/MAINTAINERS b/MAINTAINERS
index d329b05..276e79b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2850,6 +2850,13 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input.git
 S:	Maintained
 F:	drivers/input/
 
+INTEL IDLE DRIVER
+M:	Len Brown <lenb@...nel.org>
+L:	linux-pm@...ts.linux-foundation.org
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-idle-2.6.git
+S:	Supported
+F:	drivers/idle/intel_idle.c
+
 INTEL FRAMEBUFFER DRIVER (excluding 810 and 815)
 M:	Maik Broemme <mbroemme@...sserver.de>
 L:	linux-fbdev@...r.kernel.org
diff --git a/drivers/Makefile b/drivers/Makefile
index f42a030..91874e0 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -10,6 +10,7 @@ obj-$(CONFIG_PCI)		+= pci/
 obj-$(CONFIG_PARISC)		+= parisc/
 obj-$(CONFIG_RAPIDIO)		+= rapidio/
 obj-y				+= video/
+obj-y				+= idle/
 obj-$(CONFIG_ACPI)		+= acpi/
 obj-$(CONFIG_SFI)		+= sfi/
 # PnP must come after ACPI since it will eventually need to check if acpi
@@ -91,7 +92,6 @@ obj-$(CONFIG_EISA)		+= eisa/
 obj-y				+= lguest/
 obj-$(CONFIG_CPU_FREQ)		+= cpufreq/
 obj-$(CONFIG_CPU_IDLE)		+= cpuidle/
-obj-y				+= idle/
 obj-$(CONFIG_MMC)		+= mmc/
 obj-$(CONFIG_MEMSTICK)		+= memstick/
 obj-$(CONFIG_NEW_LEDS)		+= leds/
diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
index deefa85..b2a6d73 100644
--- a/drivers/acpi/processor_driver.c
+++ b/drivers/acpi/processor_driver.c
@@ -922,9 +922,13 @@ static int __init acpi_processor_init(void)
 		return -ENOMEM;
 #endif
 
-	if (!cpuidle_register_driver(&acpi_idle_driver))
+	if (!cpuidle_register_driver(&acpi_idle_driver)) {
 		printk(KERN_DEBUG "ACPI: %s registered with cpuidle\n",
 			acpi_idle_driver.name);
+	} else {
+                printk(KERN_DEBUG "ACPI: intel_idle yielding to %s",
+                        cpuidle_get_driver()->name);
+	}
 
 	result = acpi_bus_register_driver(&acpi_processor_driver);
 	if (result < 0)
diff --git a/drivers/idle/Kconfig b/drivers/idle/Kconfig
index f15e90a..fb5c518 100644
--- a/drivers/idle/Kconfig
+++ b/drivers/idle/Kconfig
@@ -1,3 +1,14 @@
+config INTEL_IDLE
+	tristate "Cpuidle Driver for Intel Processors"
+	depends on CPU_IDLE
+	depends on X86
+	depends on CPU_SUP_INTEL
+	depends on EXPERIMENTAL
+	help
+	  Enable intel_idle, a cpuidle driver that includes knowledge of
+	  native Intel hardware idle features.  The acpi_idle driver
+	  can be configured at the same time, in order to handle
+	  processors intel_idle does not support.
 
 menu "Memory power savings"
 depends on X86_64
diff --git a/drivers/idle/Makefile b/drivers/idle/Makefile
index 5f68fc3..23d295c 100644
--- a/drivers/idle/Makefile
+++ b/drivers/idle/Makefile
@@ -1,2 +1,3 @@
 obj-$(CONFIG_I7300_IDLE)			+= i7300_idle.o
+obj-$(CONFIG_INTEL_IDLE)			+= intel_idle.o
 
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
new file mode 100755
index 0000000..12f31d9
--- /dev/null
+++ b/drivers/idle/intel_idle.c
@@ -0,0 +1,446 @@
+/*
+ * intel_idle.c - native hardware idle loop for modern Intel processors
+ *
+ * Copyright (c) 2010, Intel Corporation.
+ * Len Brown <len.brown@...el.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/*
+ * intel_idle is a cpuidle driver that loads on specific Intel processors
+ * in lieu of the legacy ACPI processor_idle driver.  The intent is to
+ * make Linux more efficient on these processors, as intel_idle knows
+ * more than ACPI, as well as make Linux more immune to ACPI BIOS bugs.
+ */
+
+/*
+ * Design Assumptions
+ *
+ * All CPUs have same idle states as boot CPU
+ *
+ * Chipset BM_STS (bus master status) bit is a NOP
+ * 	for preventing entry into deep C-stats
+ */
+
+/*
+ * Known issues
+ *
+ * The driver currently initializes for_each_online_cpu() upon modprobe.
+ * It it unaware cpu online/offline and cpui hotplug
+ *
+ * ACPI has a .suspend hack to turn off deep c-statees during suspend
+ * to avoid complications with the lapic timer workaround
+ * will need to address that situation here too.
+ *
+ * There is currently no automatic probing/loading mechanism
+ * if the driver is built as a module.
+ */
+
+/*
+ * todo test
+ * test: build & run with acpi=off
+ * test: repeated load/unload
+ * test: suspend/resume vs timer workaround
+ */
+
+/*
+ * todo cpuidle
+ * 	cpuidle should supply the counters for each driver
+ * 	since they are private to cpuidle, not the driver
+ */
+
+
+/* un-comment DEBUG to enable pr_debug() statements */
+#define DEBUG
+
+#include <linux/kernel.h>
+#include <linux/cpuidle.h>
+#include <linux/clockchips.h>
+#include <linux/hrtimer.h>	/* ktime_get_real() */
+#include <trace/events/power.h>
+#include <linux/sched.h>
+
+#define INTEL_IDLE_VERSION "0.3"
+#define PREFIX "intel_idle: "
+
+#define MWAIT_SUBSTATE_MASK	(0xf)
+#define MWAIT_CSTATE_MASK	(0xf)
+#define MWAIT_SUBSTATE_SIZE	(4)
+#define MWAIT_MAX_NUM_CSTATES	8
+#define CPUID_MWAIT_LEAF (5)
+#define CPUID5_ECX_EXTENSIONS_SUPPORTED (0x1)
+#define CPUID5_ECX_INTERRUPT_BREAK	(0x2)
+
+#define mwait_hint_to_cstate(hint) ((((hint) >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK) + 1)
+#define lapic_timer_reliable(cstate) (lapic_timer_reliable_states & (1 << (cstate)))
+
+static struct cpuidle_driver intel_idle_driver = {
+	.name = "intel_idle",
+	.owner = THIS_MODULE,
+};
+static int max_cstate = MWAIT_MAX_NUM_CSTATES - 1;	/* intel_idle.max_cstate=0 disables driver */
+static int power_policy = 7; /* 0 = max perf; 15 = max powersave */
+
+static unsigned int substates;
+#define get_num_mwait_substates(cstate) ((substates >> ((cstate) * 4)) && 0xF)
+
+/* Reliable LAPIC Timer States, bit 1 for C1 etc.  */
+static unsigned int lapic_timer_reliable_states;
+
+static struct cpuidle_device *intel_idle_cpuidle_devices;
+static int intel_idle(struct cpuidle_device *dev, struct cpuidle_state *state);
+
+/*
+ * These attributes are be visible under
+ * /sys/devices/system/cpu/cpu.../cpuidle/state.../
+ *
+ * name 
+ * 	Hardware name of the state, from datasheet
+ * desc
+ * 	MWAIT param
+ * driver_data
+ * 	token passed to intel_idle()
+ * flags
+ * 	CPUIDLE_FLAG_TIME_VALID
+ * 		we return valid times in all states
+ * 	CPUIDLE_FLAG_SHALLOW
+ * 		lapic timer keeps running
+ * exit_latency
+ * 	[usec]
+ * power_usage
+ * 	mW (TBD)
+ * target_residency
+ * 	currently we multiply exit_latency by 4
+ * 	[usec]
+ * usage
+ * 	instance counter
+ * time
+ * 	residency counter [usec]
+ */
+
+static struct cpuidle_state *cpuidle_state_table;
+
+/*
+ * States are indexed by the cstate number,
+ * which is also the index into the MWAIT hint array.
+ * Thus C0 is a dummy.
+ */
+static struct cpuidle_state nehalem_cstates[MWAIT_MAX_NUM_CSTATES] = {
+	{ "", "", 0, 0, 0, 0, 0, 0, 0, 0},
+	{ "NHM-C1", "MWAIT 0x00", (void *) 0x00,
+		CPUIDLE_FLAG_TIME_VALID,
+		3, 1000, 6, 0, 0, &intel_idle },
+	{ "NHM-C3", "MWAIT 0x10", (void *) 0x10,
+		CPUIDLE_FLAG_TIME_VALID,
+		20, 500, 80, 0, 0, &intel_idle },
+	{ "NHM-C6", "MWAIT 0x20", (void *) 0x20,
+		CPUIDLE_FLAG_TIME_VALID,
+		200, 350, 800, 0, 0, &intel_idle },
+	{ "", "", 0, 0, 0, 0, 0, 0, 0, 0},
+	{ "", "", 0, 0, 0, 0, 0, 0, 0, 0},
+	{ "", "", 0, 0, 0, 0, 0, 0, 0, 0},
+	{ "", "", 0, 0, 0, 0, 0, 0, 0, 0}
+};
+
+static struct cpuidle_state atom_cstates[MWAIT_MAX_NUM_CSTATES] = {
+	{ "", "", 0, 0, 0, 0, 0, 0, 0, 0},
+	{ "ATM-C1", "MWAIT 0x00", (void *) 0x00,
+		CPUIDLE_FLAG_TIME_VALID,
+		1, 1000, 4, 0, 0, &intel_idle },
+	{ "ATM-C2", "MWAIT 0x10", (void *) 0x10,
+		CPUIDLE_FLAG_TIME_VALID,
+		20, 500, 80, 0, 0, &intel_idle },
+	{ "", "", 0, 0, 0, 0, 0, 0, 0, 0},
+	{ "ATM-C4", "MWAIT 0x30", (void *) 0x30,
+		CPUIDLE_FLAG_TIME_VALID,
+		100, 250, 400, 0, 0, &intel_idle },
+	{ "ATM-C6", "MWAIT 0x40", (void *) 0x40,
+		CPUIDLE_FLAG_TIME_VALID,
+		200, 150, 800, 0, 0, &intel_idle },
+	{ "", "", 0, 0, 0, 0, 0, 0, 0, 0},
+	{ "", "", 0, 0, 0, 0, 0, 0, 0, 0}
+};
+
+/*
+ * choose_substate()
+ *
+ * Run-time decision on which C-state substate to invoke
+ * If power_policy = 0, choose shallowest substate (0)
+ * If power_policy = 15, choose deepest substate
+ * If power_policy = middle, choose middle substate etc.
+ */
+static int choose_substate(int cstate)
+{
+	unsigned int num_substates;
+
+	power_policy &= 0xF;	/* valid range: 0-15 */
+	cstate &= 7;	/* valid range: 0-7 */
+
+	num_substates = get_num_mwait_substates(cstate);
+
+	if (num_substates <= 1)
+		return 0;
+	
+	return ((power_policy + (power_policy + 1) * (num_substates - 1)) / 16);
+}
+
+/**
+ * intel_idle
+ * @dev: cpuidle_device
+ * @state: cpuidle state
+ *
+ */
+static int intel_idle(struct cpuidle_device *dev, struct cpuidle_state *state)
+{
+	unsigned long ecx = 1; /* break on interrupt flag */
+	unsigned long eax = (unsigned long)cpuidle_get_statedata(state);
+	unsigned int cstate;
+	ktime_t kt_before, kt_after;
+	s64 usec_delta;
+	int cpu = smp_processor_id();
+
+	cstate = mwait_hint_to_cstate(eax);
+
+	eax = eax + choose_substate(cstate);
+
+	local_irq_disable();
+
+	if (!lapic_timer_reliable(cstate))
+		clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu); 
+
+	kt_before = ktime_get_real();
+
+	stop_critical_timings();
+#ifndef MODULE
+	trace_power_start(POWER_CSTATE, (eax >> 4) + 1);
+#endif
+	if (!need_resched()) {
+
+		__monitor((void *)&current_thread_info()->flags, 0, 0);
+		smp_mb();
+		if (!need_resched())
+			__mwait(eax, ecx);
+	}
+
+	start_critical_timings();
+
+	kt_after = ktime_get_real();
+	usec_delta = ktime_to_us(ktime_sub(kt_after, kt_before));
+
+	local_irq_enable();
+	
+	if (!lapic_timer_reliable(cstate))
+ 		clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu); 
+
+	return usec_delta;
+}
+
+
+/*
+ * intel_idle_probe()
+ */
+static int intel_idle_probe(void)
+{
+	unsigned int eax, ebx, ecx, edx;
+
+	if (max_cstate == 0) {
+		pr_debug(PREFIX "disabled\n" );
+		return -1;
+	}
+
+	if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
+		return -1;
+ 
+	if (!boot_cpu_has(X86_FEATURE_MWAIT))
+		return -1;
+
+	if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
+		return -1;
+
+	cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);
+
+	if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
+		!(ecx & CPUID5_ECX_INTERRUPT_BREAK))
+			return -1;
+
+	pr_debug(PREFIX "MWAIT substates: 0x%x\n", edx);
+
+#ifdef DEBUG
+	if (substates == 0)	/* can over-ride via modparam */
+#endif
+		substates = edx;
+
+	/*
+ 	 * Bail out if non-stop TSC unavailable.
+ 	 * Nehalem and newer have it.
+ 	 *
+ 	 * Atom and Core2 will will require
+ 	 * mark_tsc_unstable("TSC halts in idle")
+ 	 * when have a state deeper than C1
+ 	 */
+	if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
+		return -1;
+
+	if (boot_cpu_has(X86_FEATURE_ARAT))	/* Always Reliable APIC Timer */
+		lapic_timer_reliable_states = 0xFFFFFFFF;
+
+	if (boot_cpu_data.x86 != 6)	/* family 6 */
+		return -1;
+
+	switch (boot_cpu_data.x86_model) {
+
+	case 0x1A:	/* Core i7, Xeon 5500 series */
+	case 0x1E:	/* Core i7 and i5 Processor - Lynnfield, Jasper Forest */
+	case 0x1F:	/* Core i7 and i5 Processor - Nehalem */
+	case 0x2E:	/* Nehalem-EX Xeon */
+		lapic_timer_reliable_states = (1 << 1);	 /* C1 */
+
+	case 0x25:	/* Westmere */
+	case 0x2C:	/* Westmere */
+
+		cpuidle_state_table = nehalem_cstates;
+		break;
+#ifdef notyet
+	case 0x1C:	/* 28 - Atom Processor */
+		cpuidle_state_table = atom_cstates;
+		break;
+#endif
+
+	case 0x17:	/* 23 - Core 2 Duo */
+		lapic_timer_reliable_states = (1 << 2) | (1 << 1); /* C2, C1 */
+
+	default:
+		pr_debug(PREFIX "does not run on family %d model %d\n",
+			boot_cpu_data.x86, boot_cpu_data.x86_model);
+		return -1;
+	}
+
+	pr_debug(PREFIX "v" INTEL_IDLE_VERSION
+		" model 0x%X\n", boot_cpu_data.x86_model);
+
+pr_debug(PREFIX "lapic_timer_reliable_states 0x%x\n", lapic_timer_reliable_states);
+	return 0;
+}
+
+/*
+ * intel_idle_cpuidle_devices_init()
+ * allocate, initialize, register cpuidle_devices
+ */
+static int intel_idle_cpuidle_devices_init(void)
+{
+	int i, cstate;
+	struct cpuidle_device *dev;
+
+	intel_idle_cpuidle_devices = alloc_percpu(struct cpuidle_device);
+	if (intel_idle_cpuidle_devices == NULL)
+		return -1;
+
+	for_each_online_cpu(i) {
+		dev = per_cpu_ptr(intel_idle_cpuidle_devices, i);
+
+		dev->state_count = 1;
+
+		for (cstate = 1; cstate < MWAIT_MAX_NUM_CSTATES; ++cstate) {
+			int num_substates;
+
+			if (cstate > max_cstate) {
+				printk(PREFIX "max_cstate %d exceeded", max_cstate);
+				break;
+			}
+
+			/* does the state exist in CPUID.MWAIT? */
+			num_substates = get_num_mwait_substates(cstate);
+			if (num_substates == 0)
+				continue;
+
+			/* does the state exist in the driver's table? */
+			if (cpuidle_state_table[cstate].name == NULL) {
+				pr_debug(PREFIX "unaware of model 0x%x MWAIT %x\
+					please contact lenb@...nel.org", boot_cpu_data.x86_model, cstate);
+				continue;
+			}
+			dev->states[dev->state_count] = cpuidle_state_table[cstate];	/* structure copy */
+			dev->state_count += 1;
+		}
+
+		dev->cpu = i;
+		if (cpuidle_register_device(dev)) {
+			pr_debug(PREFIX "cpuidle_register_device %d failed!\n", i);
+			free_percpu(intel_idle_cpuidle_devices);
+			return -EIO;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * intel_idle_cpuidle_devices_uninit()
+ * unregister, free cpuidle_devices
+ */
+static void intel_idle_cpuidle_devices_uninit(void)
+{
+	int i;
+	struct cpuidle_device *dev;
+
+	for_each_online_cpu(i) {
+		dev = per_cpu_ptr(intel_idle_cpuidle_devices, i);
+		cpuidle_unregister_device(dev);
+	}
+
+	free_percpu(intel_idle_cpuidle_devices);
+	return;
+}
+
+static int intel_idle_init(void) 
+{
+
+	if (intel_idle_probe())
+		return -1;
+
+	if (cpuidle_register_driver(&intel_idle_driver)) {
+		pr_debug(PREFIX "unable to register with cpuidle due to %s",
+			cpuidle_get_driver()->name);
+		return -1;
+	}
+
+	if (intel_idle_cpuidle_devices_init()) {
+		cpuidle_unregister_driver(&intel_idle_driver);
+		return -1;
+	}
+
+	return 0;	
+}
+
+static void __exit intel_idle_exit(void)
+{
+	intel_idle_cpuidle_devices_uninit();
+	cpuidle_unregister_driver(&intel_idle_driver);
+
+	return;
+}
+
+module_init(intel_idle_init);
+module_exit(intel_idle_exit);
+
+module_param(power_policy, int, 0644);
+module_param(max_cstate, int, 0444);
+#ifdef DEBUG
+module_param(substates, int, 0444);
+#endif
+
+MODULE_AUTHOR("Len Brown <len.brown@...el.com>");
+MODULE_DESCRIPTION("Cpuidle driver for Intel Hardware v" INTEL_IDLE_VERSION);
+MODULE_LICENSE("GPL");
-- 
1.6.0.6

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