[RFC PATCH 3/3] cpuidle: big.LITTLE: vexpress-TC2 CPU idle driver
Lorenzo Pieralisi
lorenzo.pieralisi at arm.com
Thu Jul 25 07:14:26 EDT 2013
The big.LITTLE architecture is composed of two clusters of cpus. One cluster
contains less powerful but more energy efficient processors and the other
cluster groups the powerful but energy-intensive cpus.
The TC2 testchip implements two clusters of CPUs (A7 and A15 clusters in
a big.LITTLE configuration) connected through a CCI interconnect that manages
coherency of their respective L2 caches and intercluster distributed
virtual memory messages (DVM).
TC2 testchip integrates a power controller that manages cores resets, wake-up
IRQs and cluster low-power states. Power states are managed at cluster
level, which means that voltage is removed from a cluster iff all cores
in a cluster are in a wfi state. Single cores can enter a reset state
which is identical to wfi in terms of power consumption but simplifies the
way cluster states are entered.
This patch provides a multiple driver CPU idle implementation for TC2
which paves the way for a generic big.LITTLE idle driver for all
upcoming big.LITTLE based systems on chip.
The driver relies on the MCPM infrastructure to coordinate and manage
core power states; in particular MCPM allows to suspend specific cores
and hides the CPUs coordination required to shut-down clusters of CPUs.
Power down sequences for the respective clusters are implemented in the
MCPM TC2 backend, with all code needed to clean caches and exit coherency.
The multiple driver CPU idle infrastructure allows to define different
C-states for big and little cores, determined at boot by checking the
part id of the possible CPUs and initializing the respective logical
masks in the big and little drivers.
Current big.little systems are composed of A7 and A15 clusters, as
implemented in TC2, but in the future that may change and the driver
will have evolve to retrieve what is a 'big' cpu and what is a 'little'
cpu in order to build the correct topology.
Cc: Kevin Hilman <khilman at linaro.org>
Cc: Amit Kucheria <amit.kucheria at linaro.org>
Cc: Olof Johansson <olof at lixom.net>
Cc: Nicolas Pitre <nicolas.pitre at linaro.org>
Cc: Rafael J. Wysocki <rjw at sisk.pl>
Signed-off-by: Daniel Lezcano <daniel.lezcano at linaro.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
---
MAINTAINERS | 9 ++
drivers/cpuidle/Kconfig | 10 ++
drivers/cpuidle/Makefile | 1 +
drivers/cpuidle/cpuidle-big_little.c | 187 +++++++++++++++++++++++++++++++++++
4 files changed, 207 insertions(+)
create mode 100644 drivers/cpuidle/cpuidle-big_little.c
diff --git a/MAINTAINERS b/MAINTAINERS
index bf61e04..01f1b3d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2263,6 +2263,15 @@ F: drivers/cpufreq/arm_big_little.h
F: drivers/cpufreq/arm_big_little.c
F: drivers/cpufreq/arm_big_little_dt.c
+CPUIDLE DRIVER - ARM BIG LITTLE
+M: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
+M: Daniel Lezcano <daniel.lezcano at linaro.org>
+L: linux-pm at vger.kernel.org
+L: linux-arm-kernel at lists.infradead.org
+T: git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git
+S: Maintained
+F: drivers/cpuidle/cpuidle-big_little.c
+
CPUIDLE DRIVERS
M: Rafael J. Wysocki <rjw at sisk.pl>
M: Daniel Lezcano <daniel.lezcano at linaro.org>
diff --git a/drivers/cpuidle/Kconfig b/drivers/cpuidle/Kconfig
index 0e2cd5c..0f86587 100644
--- a/drivers/cpuidle/Kconfig
+++ b/drivers/cpuidle/Kconfig
@@ -42,6 +42,16 @@ config CPU_IDLE_ZYNQ
help
Select this to enable cpuidle on Xilinx Zynq processors.
+config CPU_IDLE_BIG_LITTLE
+ bool "Support for ARM big.LITTLE processors"
+ depends on ARCH_VEXPRESS_TC2_PM
+ select ARM_CPU_SUSPEND
+ select CPU_IDLE_MULTIPLE_DRIVERS
+ help
+ Select this option to enable CPU idle driver for big.LITTLE based
+ ARM systems. Driver manages CPUs coordination through MCPM and
+ define different C-states for little and big cores through the
+ multiple CPU idle drivers infrastructure.
endif
config ARCH_NEEDS_CPU_IDLE_COUPLED
diff --git a/drivers/cpuidle/Makefile b/drivers/cpuidle/Makefile
index 8767a7b..3b6445c 100644
--- a/drivers/cpuidle/Makefile
+++ b/drivers/cpuidle/Makefile
@@ -8,3 +8,4 @@ obj-$(CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED) += coupled.o
obj-$(CONFIG_CPU_IDLE_CALXEDA) += cpuidle-calxeda.o
obj-$(CONFIG_ARCH_KIRKWOOD) += cpuidle-kirkwood.o
obj-$(CONFIG_CPU_IDLE_ZYNQ) += cpuidle-zynq.o
+obj-$(CONFIG_CPU_IDLE_BIG_LITTLE) += cpuidle-big_little.o
diff --git a/drivers/cpuidle/cpuidle-big_little.c b/drivers/cpuidle/cpuidle-big_little.c
new file mode 100644
index 0000000..98cb375
--- /dev/null
+++ b/drivers/cpuidle/cpuidle-big_little.c
@@ -0,0 +1,187 @@
+/*
+ * Copyright (c) 2013 ARM/Linaro
+ *
+ * Authors: Daniel Lezcano <daniel.lezcano at linaro.org>
+ * Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
+ * Nicolas Pitre <nicolas.pitre at linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Maintainer: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
+ * Maintainer: Daniel Lezcano <daniel.lezcano at linaro.org>
+ */
+#include <linux/cpuidle.h>
+#include <linux/cpu_pm.h>
+#include <linux/slab.h>
+#include <linux/of.h>
+
+#include <asm/cpu.h>
+#include <asm/cputype.h>
+#include <asm/cpuidle.h>
+#include <asm/mcpm.h>
+#include <asm/smp_plat.h>
+#include <asm/suspend.h>
+
+static int bl_enter_powerdown(struct cpuidle_device *dev,
+ struct cpuidle_driver *drv, int idx);
+
+static struct cpuidle_driver bl_idle_little_driver = {
+ .name = "little_idle",
+ .owner = THIS_MODULE,
+ .states[0] = ARM_CPUIDLE_WFI_STATE,
+ .states[1] = {
+ .enter = bl_enter_powerdown,
+ .exit_latency = 1000,
+ .target_residency = 3500,
+ .flags = CPUIDLE_FLAG_TIME_VALID |
+ CPUIDLE_FLAG_TIMER_STOP,
+ .name = "C1",
+ .desc = "ARM little-cluster power down",
+ },
+ .state_count = 2,
+};
+
+static struct cpuidle_driver bl_idle_big_driver = {
+ .name = "big_idle",
+ .owner = THIS_MODULE,
+ .states[0] = ARM_CPUIDLE_WFI_STATE,
+ .states[1] = {
+ .enter = bl_enter_powerdown,
+ .exit_latency = 1000,
+ .target_residency = 3000,
+ .flags = CPUIDLE_FLAG_TIME_VALID |
+ CPUIDLE_FLAG_TIMER_STOP,
+ .name = "C1",
+ .desc = "ARM big-cluster power down",
+ },
+ .state_count = 2,
+};
+
+/*
+ * notrace prevents trace shims from getting inserted where they
+ * should not. Global jumps and ldrex/strex must not be inserted
+ * in power down sequences where caches and MMU may be turned off.
+ */
+static int notrace bl_powerdown_finisher(unsigned long arg)
+{
+ /* MCPM works with HW CPU identifiers */
+ unsigned int mpidr = read_cpuid_mpidr();
+ unsigned int cluster = (mpidr >> 8) & 0xf;
+ unsigned int cpu = mpidr & 0xf;
+
+ mcpm_set_entry_vector(cpu, cluster, cpu_resume);
+ /*
+ * Residency value passed to mcpm_cpu_suspend back-end
+ * has to be given clear semantics. Set to 0 as a
+ * temporary value.
+ */
+ mcpm_cpu_suspend(0);
+ /* return value != 0 means failure */
+ return 1;
+}
+
+/**
+ * bl_enter_powerdown - Programs CPU to enter the specified state
+ * @dev: cpuidle device
+ * @drv: The target state to be programmed
+ * @idx: state index
+ *
+ * Called from the CPUidle framework to program the device to the
+ * specified target state selected by the governor.
+ */
+static int bl_enter_powerdown(struct cpuidle_device *dev,
+ struct cpuidle_driver *drv, int idx)
+{
+ struct timespec ts_preidle, ts_postidle, ts_idle;
+ int ret;
+
+ /* Used to keep track of the total time in idle */
+ getnstimeofday(&ts_preidle);
+
+ cpu_pm_enter();
+
+ ret = cpu_suspend(0, bl_powerdown_finisher);
+ /* signals the MCPM core that CPU is out of low power state */
+ mcpm_cpu_powered_up();
+
+ cpu_pm_exit();
+
+ getnstimeofday(&ts_postidle);
+ ts_idle = timespec_sub(ts_postidle, ts_preidle);
+
+ dev->last_residency = ts_idle.tv_nsec / NSEC_PER_USEC +
+ ts_idle.tv_sec * USEC_PER_SEC;
+ local_irq_enable();
+ return idx;
+}
+
+static int __init bl_idle_driver_init(struct cpuidle_driver *drv, int cpu_id)
+{
+ struct cpuinfo_arm *cpu_info;
+ struct cpumask *cpumask;
+ unsigned long cpuid;
+ int cpu;
+
+ cpumask = kzalloc(cpumask_size(), GFP_KERNEL);
+ if (!cpumask)
+ return -ENOMEM;
+
+ for_each_possible_cpu(cpu) {
+ cpu_info = &per_cpu(cpu_data, cpu);
+ cpuid = is_smp() ? cpu_info->cpuid : read_cpuid_id();
+
+ /* read cpu id part number */
+ if ((cpuid & 0xFFF0) == cpu_id)
+ cpumask_set_cpu(cpu, cpumask);
+ }
+
+ drv->cpumask = cpumask;
+
+ return 0;
+}
+
+static int __init bl_idle_init(void)
+{
+ int ret;
+ /*
+ * Initialize the driver just for a compliant set of machines
+ */
+ if (!of_machine_is_compatible("arm,vexpress,v2p-ca15_a7"))
+ return -ENODEV;
+ /*
+ * For now the differentiation between little and big cores
+ * is based on the part number. A7 cores are considered little
+ * cores, A15 are considered big cores. This distinction may
+ * evolve in the future with a more generic matching approach.
+ */
+ ret = bl_idle_driver_init(&bl_idle_little_driver,
+ ARM_CPU_PART_CORTEX_A7);
+ if (ret)
+ return ret;
+
+ ret = bl_idle_driver_init(&bl_idle_big_driver, ARM_CPU_PART_CORTEX_A15);
+ if (ret)
+ goto out_uninit_little;
+
+ ret = cpuidle_register(&bl_idle_little_driver, NULL);
+ if (ret)
+ goto out_uninit_big;
+
+ ret = cpuidle_register(&bl_idle_big_driver, NULL);
+ if (ret)
+ goto out_unregister_little;
+
+ return 0;
+
+out_unregister_little:
+ cpuidle_unregister(&bl_idle_little_driver);
+out_uninit_big:
+ kfree(bl_idle_big_driver.cpumask);
+out_uninit_little:
+ kfree(bl_idle_little_driver.cpumask);
+
+ return ret;
+}
+device_initcall(bl_idle_init);
--
1.8.2.2
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